research articles on dreams

July 26, 2011

The Science Behind Dreaming

New research sheds light on how and why we remember dreams--and what purpose they are likely to serve

By Sander van der Linden

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For centuries people have pondered the meaning of dreams. Early civilizations thought of dreams as a medium between our earthly world and that of the gods. In fact, the Greeks and Romans were convinced that dreams had certain prophetic powers. While there has always been a great interest in the interpretation of human dreams, it wasn’t until the end of the nineteenth century that Sigmund Freud and Carl Jung put forth some of the most widely-known modern theories of dreaming. Freud’s theory centred around the notion of repressed longing -- the idea that dreaming allows us to sort through unresolved, repressed wishes. Carl Jung (who studied under Freud) also believed that dreams had psychological importance, but proposed different theories about their meaning.

Since then, technological advancements have allowed for the development of other theories. One prominent neurobiological theory of dreaming is the “activation-synthesis hypothesis,” which states that dreams don’t actually mean anything: they are merely electrical brain impulses that pull random thoughts and imagery from our memories. Humans, the theory goes, construct dream stories after they wake up, in a natural attempt to make sense of it all. Yet, given the vast documentation of realistic aspects to human dreaming as well as indirect experimental evidence that other mammals such as cats also dream, evolutionary psychologists have theorized that dreaming really does serve a purpose. In particular, the “threat simulation theory” suggests that dreaming should be seen as an ancient biological defence mechanism that provided an evolutionary advantage because of  its capacity to repeatedly simulate potential threatening events – enhancing the neuro-cognitive mechanisms required for efficient threat perception and avoidance.

So, over the years, numerous theories have been put forth in an attempt to illuminate the mystery behind human dreams, but, until recently, strong tangible evidence has remained largely elusive.

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Yet, new research published in the Journal of Neuroscience provides compelling insights into the mechanisms that underlie dreaming and the strong relationship our dreams have with our memories. Cristina Marzano and her colleagues at the University of Rome have succeeded, for the first time, in explaining how humans remember their dreams. The scientists predicted the likelihood of successful dream recall based on a signature pattern of brain waves. In order to do this, the Italian research team invited 65 students to spend two consecutive nights in their research laboratory.

During the first night, the students were left to sleep, allowing them to get used to the sound-proofed and temperature-controlled rooms. During the second night the researchers measured the student’s brain waves while they slept. Our brain experiences four types of electrical brain waves: “delta,” “theta,” “alpha,” and “beta.” Each represents a different speed of oscillating electrical voltages and together they form the electroencephalography (EEG). The Italian research team used this technology to measure the participant’s brain waves during various sleep-stages. (There are five stages of sleep; most dreaming and our most intense dreams occur during the REM stage.) The students were woken at various times and asked to fill out a diary detailing whether or not they dreamt, how often they dreamt and whether they could remember the content of their dreams.

While previous studies have already indicated that people are more likely to remember their dreams when woken directly after REM sleep, the current study explains why. Those participants who exhibited more low frequency theta waves in the frontal lobes were also more likely to remember their dreams.

This finding is interesting because the increased frontal theta activity the researchers observed looks just like the successful encoding and retrieval of autobiographical memories seen while we are awake. That is, it is the same electrical oscillations in the frontal cortex that make the recollection of episodic memories (e.g., things that happened to you) possible. Thus, these findings suggest that the neurophysiological mechanisms that we employ while dreaming (and recalling dreams) are the same as when we construct and retrieve memories while we are awake.

In another recent study conducted by the same research team, the authors used the latest MRI techniques to investigate the relation between dreaming and the role of deep-brain structures. In their study, the researchers found that vivid, bizarre and emotionally intense dreams (the dreams that people usually remember) are linked to parts of the amygdala and hippocampus. While the amygdala plays a primary role in the processing and memory of emotional reactions, the hippocampus has been implicated in important memory functions, such as the consolidation of information from short-term to long-term memory.

The proposed link between our dreams and emotions is also highlighted in another recent study published by Matthew Walker and colleagues at the Sleep and Neuroimaging Lab at UC Berkeley, who found that a reduction in REM sleep (or less “dreaming”) influences our ability to understand complex emotions in daily life – an essential feature of human social functioning.  Scientists have also recently identified where dreaming is likely to occur in the brain.  A very rare clinical condition known as “Charcot-Wilbrand Syndrome” has been known to cause (among other neurological symptoms) loss of the ability to dream.  However, it was not until a few years ago that a patient reported to have lost her ability to dream while having virtually no other permanent neurological symptoms. The patient suffered a lesion in a part of the brain known as the right inferior lingual gyrus (located in the visual cortex). Thus, we know that dreams are generated in, or transmitted through this particular area of the brain, which is associated with visual processing, emotion and visual memories.

Taken together, these recent findings tell an important story about the underlying mechanism and possible purpose of dreaming.

Dreams seem to help us process emotions by encoding and constructing memories of them. What we see and experience in our dreams might not necessarily be real, but the emotions attached to these experiences certainly are. Our dream stories essentially try to strip the emotion out of a certain experience by creating a memory of it. This way, the emotion itself is no longer active.  This mechanism fulfils an important role because when we don’t process our emotions, especially negative ones, this increases personal worry and anxiety. In fact, severe REM sleep-deprivation is increasingly correlated to the development of mental disorders. In short, dreams help regulate traffic on that fragile bridge which connects our experiences with our emotions and memories.

Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook, a Pulitzer prize-winning journalist at the Boston Globe. He can be reached at garethideas AT gmail.com or Twitter @garethideas .

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Special issue of the APA journal Dreaming, Vol. 15, No. 3, September 2005. Includes articles about REM dreaming in the transition from late childhood to adolescence; influence of gender and age; trauma, dreaming, and psychological distress; children's interpretation of auditory messages in divine dreams; and earliest remembered dreams.

Special issue of the APA journal Dreaming, Vol. 14, No. 2/3, June/September 2004. Includes articles about dreaming in a number of different cultures around the world.

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• Open access
• Published: 02 October 2023

Evidence for an emotional adaptive function of dreams: a cross-cultural study

• David R. Samson 1 , 2 ,
• Alice Clerget 3 ,
• Noor Abbas 1 ,
• Jeffrey Senese 1 ,
• Mallika S. Sarma 4 ,
• Sheina Lew-Levy 5 ,
• Ibrahim A. Mabulla 6 ,
• Audax Z. P. Mabulla 6 ,
• Valchy Miegakanda 7 ,
• Francesca Borghese 3 ,
• Pauline Henckaerts 3 ,
• Sophie Schwartz 3 ,
• Virginie Sterpenich 3 ,
• Lee T. Gettler 8 ,
• Adam Boyette 5 ,
• Alyssa N. Crittenden 9 &
• Lampros Perogamvros 3 , 10 , 11  

Scientific Reports volume  13 , Article number:  16530 ( 2023 ) Cite this article

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• Anthropology

The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forager societies. Here, we analyze dream content with cross-cultural comparisons between the BaYaka (Rep. of Congo) and Hadza (Tanzania) foraging groups and Global North populations, to test the hypothesis that dreams in forager groups serve a more effective emotion regulation function due to their strong social norms and high interpersonal support. Using a linear mixed effects model we analyzed 896 dreams from 234 individuals across these populations, recorded using dream diaries. Dream texts were processed into four psychosocial constructs using the Linguistic Inquiry and Word Count (LIWC-22) dictionary. The BaYaka displayed greater community-oriented dream content. Both the BaYaka and Hadza exhibited heightened threat dream content, while, at the same time, the Hadza demonstrated low negative emotions in their dreams. The Global North Nightmare Disorder group had increased negative emotion content, and the Canadian student sample during the COVID-19 pandemic displayed the highest anxiety dream content. In conclusion, this study supports the notion that dreams in non-clinical populations can effectively regulate emotions by linking potential threats with non-fearful contexts, reducing anxiety and negative emotions through emotional release or catharsis. Overall, this work contributes to our understanding of the evolutionary significance of this altered state of consciousness.

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Introduction.

Why do humans dream? As a product of the brain’s neurophysiology, our species can produce hallucinatory experiences during sleep. These dream experiences represent an altered state of consciousness. Why is it that we exhibit this altered state of consciousness rather than experiencing sleep in total perception quiescence? Research investigating dream content reveals that the dream state of consciousness, which is most often expressed in rapid-eye movement (REM), appears to be preoccupied with world simulation with content often reflecting the self’s social realities 1 , 2 , social networks 3 , 4 , and dangers 5 . Yet, whether dreams could enhance cognitive, affective, or social adaptation has been a question of active debate for decades.

A common framework for explaining the function of dreams is provided by simulation theories , which are based on the premise that dreams have a biological function and reflect selective pressures and fitness enhancement in the evolutionary past via altered states of consciousness 6 . Accordingly, dreams are credible real-world analogs 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 that prime the individual for corresponding contexts encountered in waking life. From this perspective, it has been argued that the phenotypic expression of dreaming could meet the necessary criteria for evolution by natural selection 15 .

Dream simulation and emotion regulation

Emerging work integrating neuroscience and dream content analysis suggests that emotional experiences are a crucial part of the virtual-world simulation of dreams and support an adaptive process that contributes to the resolution of emotional distress and preparation for future affective reactions 6 , 16 , 17 , 18 , 19 . In this context, the threat simulation theory 6 and social simulation theory 9 posit that dreams are biased to simulate threatening and social situations respectively. Such a mechanism would, in turn, promote adjusted behavioral responses in real-life situations 5 , 9 . Other studies have also supported the idea that past negative memories are reprocessed and combined in dreams with new, realistic, and safe contexts, suggesting the possibility of desensitization 20 , 21 or extinction 17 functions for dreaming. Functional dreams could thus expose us to threatening situations while providing us with efficient solutions to these situations. Such a process may facilitate the resolution of current social and emotional internal conflict 16 , 22 , a process also called emotional catharsis 23 , and the reduction of next-day negative mood 24 .

Together, these proposals and empirical observations suggest a potential core function of dreams via simulating distress in a safe environment to help process threats in beneficial ways; as such, functional dreams would strongly contribute to efficient emotion regulation in wakefulness 18 . These mechanisms seem to be impaired in clinical populations, such as patients with nightmare disorder 17 , 25 and anxiety disorders 26 —two pathologies characterized by less efficient fear extinction 17 , 27 .

Indeed, anxiety is considered a maladaptive emotional response implicating dysfunction of inhibitory (extinction) learning 27 , and the persistence of the fear response across time. We would thus expect that dreams with high levels of anxiety and negative emotions in the presence of a threat, as those found in clinical populations, would not serve the emotional processing function of dreams, as no emotional resolution is achieved. Critically, Revonsuo posited that the adaptive emotional function of dreams may be particularly relevant to contemporary small-scale societies facing routine ecological risks such as infectious disease and predation, as the emotional simulating mechanism would be fully activated in the face of the kinds of challenges within their environment 6 . Although there is some preliminary evidence for this argument 5 , 28 , 29 , such arguments have yet to be comparatively tested with large, multicultural datasets.

The importance of cross-cultural testing of dream content

The major challenge to the scientific investigation of dream function remains a sampling problem. To date, most dream studies have been conducted in the Global North—and primarily in the U.S. and European settings with samples of limited socio-economic and racial/ethnic breadth. Thus, one critical challenge to overcome limitations in past dream-based research, is to test the function of dreams by generating dream content variation among diverse populations’ socio-ecological experiences. This may be due in part to the interest of sleep researchers in pairing such work with sleep-based physiological techniques (i.e. polysomnography) that have been historically limited to lab settings (but see 30 for field-based methods in human biology and sleep research that are gaining momentum). While historically dreams have been the subject of anthropological investigation 28 , 31 , 32 , 33 , this ethnographic work is largely descriptive. Hence, much of the dream data are generated from studies that represent a very narrow range of human experiences for select populations (e.g., college undergraduates) at specific historical moments (e.g., between 1970 and 1990) in particular locations (e.g., U.S., Europe) and under similar societal and economic contexts (e.g., educated, high income).

There is a dearth of direct empirical tests of the evolutionary function of dreams, including comparative perspectives that would enable us to assess variation across cultural and ecological contexts in relation to dream content 9 . For example, smaller-scale societies that engage in mixed-subsistence foraging (i.e., hunt and gather for a large part of their diet), often differ from other smaller-scale societies in important ways. The depth and breadth of egalitarianism (i.e., cultural values and practices aimed at the treatment of all individuals as equal, often with norms around avoidance of prestige and hierarchy) in many sub-tropical foraging populations is intertwined with norms of cooperative pooling of time and energetic resources, such as to help provision and care for children 34 , 35 , 36 , 37 , 38 , 39 . Such forms of egalitarianism and extensive cooperation in resource sharing and family life are thought to be critical to survival and reproduction.

In contemporary populations, including the Hadza of Tanzania and BaYaka of the Republic of the Congo forager communities we focus on here, these cooperative subsistence and social dynamics necessarily place a strong emphasis on the importance of face-to-face supportive relationships for day-to-day health, well-being, and even survival 35 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 . These communities share some broad socioecological similarities in terms of (i) continuous environmental exposure to key stimuli—such as ambient light and temperature cues—known to drive circadian entrainment (e.g., circadian driven fluctuations have been shown to influence central characteristics of dream reports 50 ), (ii) gender divisions of foraging and household labor (though varying in their intensity between the BaYaka and Hadza), (iii) ecological risk in the form of predation exposure by way of large animals, pathogens and parasites, and (iv) norms regarding egalitarianism and generous resource sharing behaviors 39 , 40 , 41 , 42 , 43 , 44 , 51 , 52 .

The community-oriented interpersonal behaviors characteristic of BaYaka and Hadza and their maintenance require high degrees of emotion regulation and social problem solving. Unlike the experience of many individuals in populations from the Global North, these foragers’ daily interactions are repeated with the same network of cooperative partners throughout their lives. Additionally, although precise estimates are difficult to assess, mortality rates are relatively higher in subsistence-level societies compared to populations with better access to emergency care and biomedical treatment 41 —a factor that may be relevant in evaluating the possible threat simulation function of dreams. Thus, foragers may experience greater threat and community oriented responses to threat in their dreams. If an adaptive function of dreams is to reinforce or rehearse such day-to-day, prosocial (i.e., community-oriented) interactions, particularly with trusted kin, then people in BaYaka and Hadza communities will have a higher representation of those interactions and family members in their dreams than would typical populations in the Global North who reside in more individualistic societies.

Hypotheses and predictions

Here, we compare the dreams of two foraging communities—the BaYaka and Hadza—to non-clinical and clinical (i.e., with nightmares and social anxiety) populations from the Global North. First, because of their strong egalitarian social norms and high levels of daily face-to-face interpersonal support from trusted family and friends, we predict that the dream content of both forager groups will have a greater frequency of community-oriented behaviors when compared to dreamers in the Global North. Second, given that both forager groups experience greater early-to-midlife mortality—subsequently leading to a greater chance of an individual losing their own life, the life of offspring, kin, or friends—we predict a greater frequency of threat related dream content relevant to mortality. Third, we expect that foragers’ dreams will serve an efficient emotion regulation function, where threats are associated with new, non-fearful contexts/efficient solutions 17 , and, thus, with lower anxiety/negative emotions in dreams. Finally, we predict that the Nightmare group will have greater levels of negative emotions in dreams and that the student group, associated with COVID-19 pandemic, as well as the social anxiety group, will be characterized by greater anxiety in dream content. By comparing these groups, we can better understand the role of culture and environment in shaping the human experience of dreaming.

Material and methods

Participants.

In all, individuals from two sub-Saharan foraging egalitarian communities with low degrees of market integration, the Hadza and BaYaka and from three high income capitalistic populations (including non-clinical and clinical populations) totaling 234 participants contributed 896 dreams (see Table 1 for summary details).

Global North data collection and characteristics

Data from the Global North populations were drawn from previously published studies done in Switzerland, Belgium, and Canada. The Switzerland and Belgium samples were generated between 2014 and 2022 25 , 26 , 53 , 54 , 55 and included data from three groups: a non-patient group of young healthy participants, patients suffering from social anxiety disorder (SAD), and patients suffering from nightmare disorder. Participants in these studies all kept the same sleep and dream diary (for details see 18 ). During the night or every morning, upon spontaneous awakening, the participants were asked to report whether they had a dream with or without recall or no dream at all. They also reported the presence of specific emotions thanks to dichotomous questions (presence/absence); in total, eleven emotions could be reported. A twelfth choice was reserved to the “absence of emotions”. In the last section of the dream diary, they were also asked to freely write down the dreams they had experienced during their sleep.

The non-clinical reference control group in the Global North includes 219 participants (123 females). A subset of 103 participants, aged between 16 and 40 years old (M = 22.1, SD = 7.9), had dream word counts equal to or greater than 20 words and were included in the dream analysis (word average per dream = 78.2, SD = 66.0). All participants followed a constant sleep schedule during the days preceding the experiment to assess the mean sleep duration and exclude any circadian disturbance or sleep disorder. People suffering from mental disorders were excluded. Ethical approval was granted by the committee of the Faculty of Medicine of the University of Liege and by the Ethical Committee of the Canton of Geneva.

Dreams were also collected from patients suffering from social anxiety disorder (SAD) according to The Diagnostic and Statistical Manual of Mental Disorders (DSM5) 26 , 56 . SAD is characterized by a persistent amount of fear when confronted with social situations 57 . Forty-eight subjects (32 females) were included in the final sample, after assessment of their social anxiety disorder level. The dream diary was filled every morning upon awakening for 2 weeks. Three hundred twenty-four (324) dream reports were collected (6.75 dreams per participant). A subset of 37 participants, aged between 16 and 40 years old (M = 24.4, SD =7.9), had dream word counts equal to or greater than 20 words and were included in the dream analysis (word average per dream = 76.9, SD = 56.7). Ethical approval was granted by the Ethical Committee of the Canton of Geneva, Switzerland (“Commission Cantonale d’Ethique de la Recherche sur l’être humain”).

Additionally, dreams were collected in individuals suffering from nightmare disorder 25 . In total, 36 patients (27 females) were included. All of them suffered from nightmare disorder according to DSM5 with at least moderate severity (> 1 episode per week). Every morning upon awakening participants filled in a dream diary for 2 weeks. One hundred thirty-four (134) dream reports were collected (3.72 dreams per participant). A subset of 33 participants, aged from 20 to 35 years old (M = 26.3, SD = 8.4), had dream word counts equal to or greater than 20 words and were included in the dream analysis (word average per dream = 43.5, SD = 23.8). Ethical approval was granted by the Ethical Committee of the Canton of Geneva, Switzerland (“Commission Cantonale d’Ethique de la Recherche sur l’être humain”).

Altogether, the Belgian and Swiss studies had 924 dream reports collected from the dream diary over 397 nights (4.2 dreams per participant on average). Of those dreams the number that were included in the final analysis with words counts equal to or above 20 are as follows: control N  = 356, Nightmare Disorder N  = 113, and SAD  = 184.

Students at the University of Toronto contributed dream reports ( N  = 184) collected during the fourth wave of the COVID-19 pandemic, where the proliferation of COVID-19 variants was of major concern in Ontario, Canada, as announced by the Public Health Agency of Canada (Statistics Canada, 2021). In total, 24 students (21 females) aged from 19 to 25 years old (M = 21.9, SD = 5.5) were included. Ethics was approved and attained by the University of Toronto REB (RIS Human Protocol Number 39768). During this time, self-rated mental health was below national average (< 50%), and 82% of the Canadian population that were eligible for vaccination were fully vaccinated, however restrictions were still imposed in most areas, including mask-wearing, and limiting contacts. Thus, explorations of evolutionary theories on dream functions may have special relevance during the COVID-19 pandemic 58 , 59 . The final number of dreams equal to or above 20 words and included in the analysis was N  = 168 (word average per dream = 120.6, SD = 44.4).

Global South data collection and characteristics

Data were collected over different time periods by different experimenters. Hadza participants ( N  = 18) were surveyed by DRS in January and February of 2016 and BaYaka participants ( N  = 19) by AHB, SLL, VM, and MSS in June and July 2017. Hadza participants were aged between 18 and 68 years old (M = 42.7, SD = 8.5) and BaYaka participants were aged between 27 and 70 years old (M = 42.3, SD = 10). Combined, we collected a total of 101 dream reports (2.16 dreams per participant and a word average per dream = 38.7, SD = 18.9). The Hadza contributed 48 dream reports (female dreams = 12, male dreams = 36; word average per dream = 44.4, SD = 20.6); all Hadza dreams were equal to or greater than 20 words and were included in the analysis. The BaYaka ( N  = 19) contributed 53 dream reports (females dreams = 26, male dreams = 27); twenty-seven BaYaka dreams were equal to or greater than 20 words (word average per dream = 28.7, SD = 9.1) and were included in the analysis.

Dream reports were collected in the field using a modified Most Recent Dream (MRD) method 60 as a template for questionnaires, and in practice (as the indigenous populations could not write) were a daily verbally administered dream diary. The instructions, given by field researchers in morning after a sleep period, requested the participant to recall whether they dreamt the previous night. If subjects answered in the affirmative, they were then asked to recount the details of the dream using the MRD method template. The report was expected to be detailed, including a description of the dream's setting, the people involved (their age, sex, and relationship to the participant), and any animals present in the dream. Participants were also instructed to describe their emotions during the dream and whether it was a positive or negative experience. This method is ideal for use in small-scale societies because it is a fast, inexpensive, and reliable way to obtain large samples of dream reports. For both forager groups, dream content was translated by the aid of a multilingual field assistant at the time the dream was recorded. Importantly, it is essential to note that, as both the MRD modified and verbally administered dream diary (Global South) and the classic Dream Diary method (Global North) recorded dreams of the previous night, they shared a similar approach and were directly comparable. Additionally, both were administered shortly after awakening from sleep on the same day as the dream, thereby minimizing potential memory biases 61 .

For work with the Hadza, IRB approval was granted from the University of Nevada, Las Vegas (2014) and verbal consent for participation was asked to each participant in Swahili, the second language of the Hadza community. All research was performed with approval of the government of Tanzania, via the Tanzanian Commission for Science and Technology (COSTECH) and the Tanzanian National Institute for Medical Research (NIMR). For the BaYaka, village council consent for this study was obtained at a community meeting in 2015. Subsequently, community consent was annually renewed. Verbal consent was provided by each participant following recruitment into this study. Approval to conduct research in the Republic of the Congo was given by The Centre de Recherche et D’Edudes en Sciences Sociales et Humaines. Ethics approval was obtained from Duke University (2017), the University of Notre Dame (2017), and the University of Cambridge (2017).

All methods were performed in accordance with the relevant guidelines and regulations, and informed consent was obtained from all participants.

Dream text analysis

LIWC-22 is an acronym for Linguistic Inquiry and Word Count, and it is a text analysis software program that can return results for up to 90 different variables or categories 62 . The English text analysis strategy employed the LIWC-22 Dictionary. This internal dictionary is comprised of over 12,000 words, phrases, and emoticons, which have been carefully selected and categorized into sub-dictionaries to assess various psychosocial constructs. Essentially, the LIWC-22 software program is designed to map linguistic constructions to important psychosocial theories and constructs, and thus, target words contained in texts that are read and analyzed by LIWC-22 are used for this purpose.

In this study, the dream texts were translated and transcribed into English, and preprocessed into four super-categories— Community-oriented (by grouping the LIWC categories: social, family, moral, friend, and prosocial) , Threat (by grouping the LIWC categories: conflict and death) , Negative emotions (encompassing the category: negative emotions), and Anxiety (encompassing the category: anxiety). To create an outcome variable for statistical models (see section ‘Modelling' ), we summed the number of words of each category in each dream text. Examples of the Community-oriented target words were: care, help, thank, please, parent, mother, father, baby, honor, deserve, judge, you, we, he, she. Examples of the Threat target words were: fight, killed, attack, death, dead, die, kill. Examples of the Negative emotions target words were: bad, hate, hurt, tired. Examples of the Anxiety target words were: worry, fear, afraid, nervous. The LIWC-22 Dictionary provides a systematic and reliable approach to text analysis 63 and has been widely used in other word-based dream content analyses 25 , 64 , 65 .

To assess the predictors of the four response variable categories ( Community-oriented, Threat, Negative emotions, Anxiety dream content) by population (BaYaka, Hadza, Nightmare, SAD, Students, and Control) we used a linear mixed effects model, built using the lme4 package and model averaged using the MuMin package 66 . To normalize the count data for each category, we square root transformed the response variable 67 , 68 . Finally, we made statistical inferences using a combination of standardized coefficients, confidence intervals, and p-values. We controlled for the fixed effects of age, number of dream reports, word count and sex as well as subject ID (to control for repeated measures) as a random effect. After assessing information criterion, models including the number of dream reports and age as fixed effects differed little from models without them, and so we removed them from final analysis. To increase the power of the model to identify the predicted patterns in the data, we obtained coefficients based on optimization of the log-likelihood using shrinkage, which incorporates measurement error into the regression model and improves less certain estimates by pooling information from more certain estimates 69 .

The non-patient sample from the Global North was used as a model reference category (i.e., a group that is used as a point of comparison for other groups in a statistical analysis) so effect-size estimates for each population are predicted differences in counts of dream content compared to this sample.

The dream content models were fit as follows:

The full dataset, along with all meta-data and more detail of each variable, is available in the Open Science Framework (OSF) data repository:  https://osf.io/7n6kf/ .

Community-oriented’ dream content is greatest in BaYaka

Amongst all sampled populations, the BaYaka showed greater community-oriented dream content than all group samples from Global North populations and Hadza population, after adjusting for sex, word count, and subject ID. As shown in Table 2 , and displayed in Fig.  1 , after factor correction, the BaYaka sample positively drives community-oriented dream content. Additionally, women’s dream reports and word count were drivers of the response variable (Table 2 ). As ethnographic data, we present a few such examples here:

‘I was walking in the forest with my two adult daughters and found a porcupine in a trap and brought it back to the village to eat it. It was a good dream’ ‘I was net hunting with my family (including extended family camp) and we caught many animals so he had to make a smoker "bota" to smoke all of them’

Prosocial dream estimates plot.

‘Threat’ dream content is greatest in BaYaka and Hadza

After adjusting for sex, word count, and controlling for repeated measures of the subject ID, both the BaYaka and Hadza samples had higher levels of threat dream content compared to the Global North groups. This is shown in Table 3 and depicted in Fig.  2 . Thus, belonging to the BaYaka or Hadza community is associated with a greater probability of experiencing threatening dream content. No other factors were found to significantly influence threat dream content.

Threat dream estimates plot.

Importantly, several dream reports gathered among the Hadza community demonstrated high threat situation to which a positive, emotionally cathartic resolution was found. For example:

‘I dreamt I was being chased by a herd of elephants; I was in Nyanza, which is open flat savanna land. I ran and found a small cave which was too small for the elephants to follow. I escaped’. ‘I was chased by an elephant in the bush around camp. I was with four unfamiliar women. I escaped by running into the mountains’. ‘I dreamt I was in the forest and the military was chasing me with guns and he climbed a tree to get away.’ ‘I was chased by a leopard in nearby mountains. I began by hunting but realized that I was the hunted. I was alone but I escaped’.

Moreover, in some Hadza dream reports, a solution to a threat was found through social support:

'I dreamt I fell into a well that is near the Hukumako area by the Dtoga people. I was with two others and one of my friends helped me get out of the well.' ‘I dreamt a buffalo hit me. I was in Numbeya bushland where we look for honey. I was looking for the "small honey". There was another man called January and he came and helped me’ ‘I dreamt a Toga not from this camp (who) took a knife and a person he didn't know from another camp. After I told the guy to stop, he left our Sengele camp.’

'Negative emotion’ dream content is greatest in Nightmare disorder sample

After adjusting for sex, word count, and subject ID, the sample of patients from the Global North in the Nightmare Disorder group had higher levels of dream content with negative emotions compared to the reference group (Table 4 and Fig.  3 ). Conversely, the Hadza exhibited significantly fewer negative emotion words in their dream content than the reference group. No other groups differed from the reference group, as shown in Table 4 and depicted in Fig.  3 . The following dream reports demonstrate high fear without resolution in the Nightmare Disorder group:

‘My mom would call me on my phone and ask me to put it on speakerphone so my sister and cousin could hear. Crying she announced to us that my little brother was dead. I was screaming in sadness and crying in pain.’ ‘I was with my boyfriend, our relationship was perfect and I felt completely fulfilled. Then he decided to abandon me, which awoke in me a deep feeling of despair and anguish.’ ‘I remember in my dream is that I was sitting at a table, in one of the secret rooms, across from a middle-aged man who said he was my uncle (he did not look like any of my uncles), and he was over 100 years old but looked like he was in his 50s. He looked like evil characters from movies. He said he was going to kill me after he went to speak with other people in the other room to admit his secret and then come to kill me. After he left the room, I got up and saw that the door was not fully closed. My thought was that I had to go fight him and then I woke up before I could approach the door.

Negative emotions dream estimates plot.

‘Anxiety’ dream content is greatest in the Canadian (COVID-19 pandemic era) student sample

After accounting for sex, the word count and participant repeated measures by subject ID, it was found that the student group had more anxiety dream content compared to the reference group. Table 5 and Fig.  4 indicate that no other groups demonstrated a significant difference from the control group. In the following two examples, the dream scenario illustrates the level of anxiety that the subject experiences as he needs to confront challenges alone:

‘The dream I remember relates to a game that I play. As it only involved myself, there was no one that I knew around, and I remember feeling anxious. I was doing a very difficult mini-game in the game where a bunch of non-player characters were all around me and I needed to hide behind obstacles to stay safe. I remember waking up once I died inside the mini-game’

Anxiety dream estimates plot.

Contrary to one of our predictions, no significant differences between the non-clinical group and the Social Anxiety Disorder group were found about the level of anxiety experienced in dreams. However, some dreams illustrate the social isolation these patients are experiencing in their real life, translated by a lack of social support when dangers arise:

‘I was in an elevator, stuck, alone. I pressed the down button, and then the elevator sped down. I was very scared, I tried to set off the emergency bell. I arrived at the bottom, it was dark and a sheet or blanket fell from the ceiling of the elevator to cover me.’

In other dreams of this group, people are regarded as hostile, which eventually increases the anxiety level:

‘I dreamed that I ran into someone I knew at the supermarket. We collided without excusing each other which led to an open conflict. The person in question threatens me, I go to the manager of the store accusing the person of having stolen something (it's not true). Then we walk out of the store and the other begs me to drop my charge of theft. I tell him that I won't go any further and that the newspapers won't know anything because I'm a journalist. The person's mother picks him up. I walk a bit until we go to their place. I explain to the person that I have the feeling of being followed by a man who looks like a shadow, and who watches over me and waits for the moment to seize me. I then understand that this man is death himself!’ ‘In my dream, I was at my high school. I went into the classroom by myself and two friends (female, 18) that I thought were close to me started isolating me during group work. I worked by myself the entire class while they acted aggressively towards me, at least verbally. I pulled out my chair to go submit my assignment and it hit a person behind me (male, 18). This person is a friend from my primary school. He shouted at me even though I tried to explain to him what happened was just an accident. I used the washroom, and my phone was water-damaged by one of the two girls (may or may not be an accident). I asked her to pay me back, but subconsciously I did not want the refund but instead to have an excuse to hold a conversation with her. It was an unpleasant dream because I thought I was close to them.’

In the present study, we tested the hypothesis that dreams serve an emotional function that is potentially adaptive by examining dream content from Hadza and BaYaka foragers, who belong to communities characterized by high levels of interpersonal support coupled with greater early-to-midlife mortality (due to predation, resource stress, food and water insecurity, and disease) in comparison to populations in the Global North. We found partial support to the first prediction, that forager dreams exhibit greater community-oriented dream content. Of all the populations examined, only BaYaka reported dreams with significantly more frequent content related to community-orientation and social support amongst family and friends (Table 2 and Fig.  1 ).

The second prediction, that foragers’ dreams contain more threat related content was supported. Both the BaYaka and Hadza samples demonstrated a greater frequency of mortality and conflict associated dream content compared to the reference group, whereas the other groups did not show such difference (Table 3 and Fig.  2 ). The prediction that dreams may augment the processing of high threat levels, yet also be characterized by low levels of both anxiety and negative emotions—was supported. The BaYaka exhibited levels of negative emotions in dreams that did not differ from the reference group, while the Hadza exhibited significantly less dream content with negative emotions compared to the reference. As expected, the Nightmare Disorder group also exhibited significantly greater levels of negative emotions in dreams (Table 4 and Fig.  3 ). A similar pattern was found with anxiety dream content, where the student group during the COVID-19 pandemic was characterized by significantly greater anxiety dream content compared to the reference group, while the BaYaka and Hadza did not differ compared to the reference group (Table 5 and Fig.  4 ).

Evidence for an emotional function of dreams in small-scale forager populations

BaYaka and Hadza foragers face several specific hazards. BaYaka communities reside in a rainforest ecology in the Congo Basin, where routine hazards (i.e., specific sources of danger include: (i) intergroup conflict with Bantu fisher-farmers due to perceived trade and labor related debt, (ii) illnesses (malaria, tuberculosis, intestinal parasites), and (iii) extrinsic risks (i.e., broader factors that can increase a person’s overall risk of harm or negative outcomes) of everyday life, including encounters with dangerous animals like snakes, elephants, crocodiles, and gorillas while hunting, fishing, and foraging as well as other hazardous aspects of the forest such as falling limbs/trees and falls while climbing 70 . The BaYaka infant mortality rate in the study region is unknown, but (as measured elsewhere in the region) can be inferred to be around 20 percent 41 . Adult and juvenile mortality is generally relatively high compared to populations with better access to emergency care and biomedical treatment, though precise estimates are currently unknown 41 . A study of death among the Aka in the Central African Republic found that infections and parasitic diseases were the most common causes of death across ages, causing 22 percent of 669 deaths, and diarrhea causing another 21 percent of deaths 71 .

The Hadza reside in a diverse ecological region characterized by rolling hills, grasslands, and acacia commiphora woodland. Hazards for the Hadza include (i) intergroup conflict with the Datoga pastoralists who co-reside in some areas of the landscape and keep large herds of cattle and goats that drink the scare water in the water holes during the dry season and eat much of the vegetation needed to support wildlife, (ii) illnesses (e.g. tuberculosis, malaria, viral diarrhea) that are faced with little access to biomedical treatment, and (iii) extrinsic risks of everyday life that include falling from trees when collecting honey, snakebites, and encounters with predators when hunting or scavenging meat 48 . One study showed that out of 75 deaths, a third of deaths were attributed to illness, with age, childbirth, poisoning or bewitching and homicide, and falling from trees as other causes of death 72 . With respect to mortality, 21% of infants die in the first year of life and 46% of juvenile children die by age 15 72 , 73 .

Comparatively, populations of the Global North face other types of threats and share different sociocultural values than individuals from small-scale societies. In contrast to collectivistic cultures, like BaYaka and Hadza, most societies of the Global North are strongly individualistic and competitive 74 . People in these societies have less routine face-to-face contact with and imperative cooperative reliance on broad kin networks. At the same time, this individualism shapes many common threats, which are mostly connected to social life (e.g., ostracism and exclusion, loss of status, shame, failure in an exam, etc.), and which are mostly experienced at an individual rather at a collective level. Although recent austerity plans resulted in the reemergence of unemployment, poverty, homelessness, and food insecurity in European and American countries 75 , economic development, public health infrastructure, and access to biomedical care have been linked to comparatively greater life expectancies in the Global North (e.g. 77 years in the U.S. and 80 years in the E.U.), with a larger proportion of deaths occurring in older age from chronic conditions 76 , 76 , 78 .

The present findings provide evidence that when compared to populations in the Global North, foragers disclose a prevalence of community-orientation in their waking life as well as the socially connected themes in their dreams, which may support emotional health. Specifically, our analysis suggests that even in the context of threat, community-orientation—expressed by strong social networks that rely daily on mutual assistance in the context of strong egalitarian social norms—may also play an important role in providing strategies to overcome threats and ultimately achieve emotion regulation. Importantly, an interpretation of BaYaka and Hadza dreams is that foragers activate both the threat simulation and extinction functions of dreaming, which may result in resolution of these threats within their dreams.

The dysfunctional nature of nightmares

We claim here, in line with other theoretical concepts 17 , that increased threat in dreams (as compared to dreams from healthy controls) does not seem to be functional without a subsequent emotional resolution. For example, patients with nightmare disorder have dreams characterized by recurrent, intense, and highly threatening content that cause significant distress and impairment in social, occupational, or other areas of functioning 56 . Nightmares are dreams with high threat but insufficient emotional resolution. The dreamer cannot find effective solutions for threats, therefore high fear and anxiety impedes emotion regulation and catharsis. According to the threat simulation theory, individuals possess a threat simulation system by which multiple factors (such as, inherited personality traits, threat input throughout adolescent development, current stress levels and recent threat input) regulate dream phenotypes. These inputs can also be attenuated by strong social support networks and egalitarian norms. Previous work has suggested that threatening content in dreams ultimately serve to strengthen waking threat perception skills and threat avoidance behaviors that help to self-cope with the challenging realities of waking life 6 , 8 , 79 , 80 .

The forager data further supports the idea that overcoming threat by way of adaptive emotional responses (in wake or sleep) is a crucial component of an efficient emotion regulation in the face of stressful events. When the presence of threats in dreams is not associated with subsequent emotional resolution, as in recurrent nightmares, dreams seem to lose their emotional processing function. Our results, along with others 81 , 82 , 83 suggest that nightmares are dysfunctional dreams with high threat simulation coupled with lack of fear extinction.

Dreams in situations of social isolation or social anxiety

Contrary to the community-oriented character of the BaYaka population, and similar to the increased negative emotions found in nightmares, the dream reports collected from students during the pandemic era were characterized by high levels of anxiety, and sometimes these manifested with themes of isolation and having to confront challenges alone (as depicted in the dream text examples in the “ Results ” section). For example, dreamers experienced high anxiety because of the presence of hostile people in the narrative, without finding any positive way to deal with such a threat. Our results suggest that dreams of individuals in situations of social isolation or social anxiety do not seem to achieve a sufficient degree of emotional resolution (see also 26 ). Whether there is a causal relationship between such a deficient extinction function of dreaming and the symptomatology of anxiety disorders is not clearly elucidated and should be further tested in the future.

Limitations

There are several limitations to the current study, particularly in regard to the dream content collection among the BaYaka and Hadza populations. Future dream research in such small-scale societies should emphasize not only generating dream data but also including daily reports of activity or evidence of daytime emotion regulation or performance 18 . Accounts for waking life experiences enable a direct analysis of dreams to experiences encountered during the day, which would then allow to test threat or social simulation hypotheses or to make claims related to these hypotheses in general 60 . Correlational studies, such as the one conducted by Sterpenich and colleagues 18 , or interventional studies (i.e., manipulating dream content and observing its effect in wakefulness 25 ) offer a closer approximation of the relationship between wake and dream functions. Importantly, observational dream research, including the present study, cannot claim to provide strong evidence for causality between wakefulness and dreams, nor for the directionality of such relationship regarding emotion regulation functions. Finally, as both a point of originality for this work and in distinction from previous work, this study did not test for the daytime emotional state-response, as emotional resolution was assessed in the dream itself.

Dream reports with greater length are more likely to contain sufficient information to accurately describe a dream 29 . Yet, some dream reports from both of these communities were relatively short in length. This can be attributed to dream recounting having to be translated and transcribed into English. Although we made efforts to recount as much detail as possible, dream descriptions could only be paraphrased summaries of dreams distilled through the translator. In addition, it is difficult to assess whether the participant recounting his/her dream was motivated and/or had sufficient practice formulating accurate long-term memories of the dream. Often, inexperienced dream recounters simply answer the questionnaire as is presented to them, which can attribute to dream report bias 80 . Despite the short dream descriptions and less formalized training in dream recounting, the BaYaka and Hadza communities are characterized by a rich storytelling culture and were typically highly motivated to discuss dreams and their interpretations. We also note that these samples are characterized by a stark lack of sexually related activity in dreams. It may well be that for these groups, the lack of recounting dreams of a sexual nature may reflect a taboo placed on descriptions of sexuality in general.

Here we provide support for the idea that in non-clinical populations with real and perceived threats, dreams may process high threat levels, yet also be characterized by low anxiety and negative emotions. Our results suggest indirectly that dreams can effectively regulate emotions by linking potential dangers with novel, non-fearful dream contexts and can lead to a reduction in feelings of anxiety and other negative emotions, as a form of emotional release or catharsis. In addition, in at least one such community (the BaYaka), emotional catharsis is often achieved by strong social support. Ultimately, if dreaming prepares human beings to face likely challenges and dangers in waking life, then our results are among the first to show these potential functions under evolutionarily relevant socio-ecological conditions.

Data availability

The data that support the findings of this study are publicly available on OSF ( https://osf.io/7n6kf/ ). 

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Acknowledgements

We would like to thank both the Hadza and BaYaka for participating in this study. We would like to thank Dambo Justin and Mékouno Paul for assistance with data collection in Congo. We would like to thank Jarno Tuominien for useful discussions and Audrey Theux for technical assistance. This project was funded by the National Geographic Society (no. 9665-15 to DS), the Jacobs Foundation (to LG and AB), the Medical Direction of University Hospitals of Geneva (PRD 18-2019-I to LP) and the Swiss National Science Foundation (CRSK-3_190722 to LP).

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Conceptualization: D.S. and L.P. Methodology, software: D.S., A.C., L.P. Data curation: D.S., A.C., N.A., J.S., M.S.S., S. L-L., F.B., P.H., V.S., L.T.G., A.B., A.N.C., L.P. Writing—original draft preparation: D.S. and L.P. Visualization, investigation: D.S., S. L-L., S.S., V.S., L.T.G., A.B., A.N.C., L.P. Supervision: D.S. and L.P. Funding acquisition: D.S., S. L-L., L.T.G., A.B., A.N.C., L.P. Writing—reviewing and editing: D.S., A.C., N.A., J.S., M.S.S., S. L-L., F.B., P.H., S.S., V.S., L.T.G., A.B., A.N.C., L.P.

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Samson, D.R., Clerget, A., Abbas, N. et al. Evidence for an emotional adaptive function of dreams: a cross-cultural study. Sci Rep 13 , 16530 (2023). https://doi.org/10.1038/s41598-023-43319-z

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April 14, 2024

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Untangling dreams and our waking lives: Latest findings in cognitive neuroscience

by Cognitive Neuroscience Society

"Dreams are messages from the deep." (Dune Part 1) Musings about dreams abound throughout society, from movies to TV to books. But despite being a constant source of fascination, the role of dreams in our lives still remains elusive.

As recently noted in the TV show Grey's Anatomy, "Honestly, no one knows why we dream or why we have nightmares." While true, neuroscientists are finding innovative new ways to study dreams and how they influence our cognition.

"Understanding how dreams are generated and what their function might be—if any—is one of science's biggest open questions right now," says Remington Mallett of University of Montréal, who is chairing a session today at the annual meeting of the Cognitive Neuroscience Society (CNS) in Toronto .

"Because we don't know much about dreams, it is hard to estimate their full impact on our waking lives. But current results suggest that indeed dreams influence our waking experiences."

As presented at CNS 2024, researchers are finding not only novel approaches to exploring dreams and the architecture of sleep, but also ways to engineer dreams to help people suffering from sleep disorders . In the process, scientists are seeing how perceptions of dreams and sleep quality often differ greatly from the objective measures traditionally used to evaluate them.

Perceptions versus reality

Claudia Picard-Deland posits that dreams are a window into understanding sleep quality. She and colleagues at the University of Montréal design studies that wake sleepers many times in the night to determine how the participants perceive their sleep.

"Dreams are not studied a lot in the context of sleep quality. The focus is more often on objective measures like brain activity or sleep stage, but I think we need to look closer at dream activity and its impact on how we perceive sleep." For people who suffer from insomnia and related disorders, perception of sleep is reality, and their dreams could offer possible ways to help shape those perceptions.

In their latest, unpublished study, Picard-Deland and colleagues woke 20 "good sleepers" some 12 times in the night, representing all four classic sleep stages at three different times in the night. At each awakening, the researchers would ask whether they had been awake or asleep, how deeply they were sleeping, what was last in their minds, and how immersed they felt in their dreams.

They found that sleep misperception—feeling awake even when electrodes measured they were asleep—was common among participants, especially in the early, dreamless stages of sleep. Likewise, they found that when the participants were able to recall their dreams, they perceived their sleep as deeper.

"And when they are more immersed in their dreams, feel more physically present, or have more vivid dreams, they wake up feeling their sleep was deeper compared to when they have no, or light, dream activity," Picard-Deland says.

The researchers were surprised to see how frequently participants thought they had been awake when they were actually sleeping ("paradoxical insomnia") and in the deeper, slow-wave phase of sleep. This work builds upon similar previous findings and has important implications for how scientists understand the architecture of sleep, as well as for people who report insomnia.

As someone who has experienced insomnia her whole life, Picard-Deland thinks it is crucial for people to realize that they may be sleeping more than they think. "It helped me to see it with my own eyes, happening in front of me, that participants were sleeping yet still felt awake."

Beyond that understanding, this work could have future applications for sleep rehabilitation based on dreams. For example, Picard-Deland would love to explore whether dream training, such as teaching people how to experience more immersive lucid dreams, could lead to better perceived sleep quality.

Lucid dreams as a tool

Lucid dreams are an important part of the work of Saba Al-Youssef whose team at Sorbonne Université leverages the ability of lucid dreamers to use facial muscles during sleep as a new tool for gathering data. "Dreams are a hidden world to which we have no direct access," she says.

"We mostly rely on dream reports no matter what study method we use. The capacity of lucid dreamers to communicate with us in real time gives us side door access to dreams, at least knowing when a specific event is happening."

In a new study with researchers at Northwestern University published in Current Biology , Al-Youssef and colleagues aim to better understand how the brain acts during dreams in comparison to its behavior when awake.

When people are awake and close their eyes, visual content disappears and specific electrical signals occur. Researchers therefore wondered what happens in the brain when someone closes their eyes in a dream. They hope to better understand the neural correlates of visual perception during dreams.

The researchers recruited participants who included lucid dreamers with narcolepsy. Over the course of five naps, the researchers instructed participants to close and open their "dream eyes" and signal so by sniffing once or twice. They then asked those with narcolepsy to report whether they had visual content in each condition by frowning or smiling.

"Surprisingly, we've found that closing our 'dream eyes' is not always accompanied by a loss of vision, as is the case when we're awake," Al-Youssef says. "I hope this work would help show how using lucid dreams can be helpful in studying dreams and even understanding their function."

Mallett is excited to see work like this to develop new methodology for studying dreams. "I think most scientists are skeptical that dreams can be studied, so before I tell them about what we found, I need to convince them that we can find something," Mallett says, "that we have the methods and tools to make discoveries about dreams."

Both Picard-Deland's and Al-Youssef's work open new avenues of research in manipulating dreams through new technology and with immediate clinical benefits. "You need to manipulate dreams for good experimentation, and you need to manipulate dreams to reduce nightmares," he says.

"Nightmares are incredibly frustrating for a variety of clinical populations, and there is great need for approaches to reducing them. Understanding how dreams are formed, and how to change them, is already laying paths forward for efficient nightmare reduction protocols."

Overall, the body of work presented at CNS 2024 is showing the myriad ways dreams affect our waking lives. "This is rather unsurprising when you consider that dreams are experiences, and your prior experience is always going to impact your experiences going forward."

The work also echoes a fundamental lesson from cognitive neuroscience, that whether awake or asleep, our perceptions of the world are but imperfect creations in our minds.

The symposium " Into the Night: The Cognitive Neuroscience of Dreaming " is taking place at 1:30pmEDT on Sunday, April 14, as part of the CNS 2024 annual meeting from April 13-16, 2024 in Toronto, Canada.

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Why Do We Dream? A New Theory on How It Protects Our Brains

W hen he was two years old, Ben stopped seeing out of his left eye. His mother took him to the doctor and soon discovered he had retinal cancer in both eyes. After chemotherapy and radiation failed, surgeons removed both his eyes. For Ben, vision was gone forever.

But by the time he was seven years old, he had devised a technique for decoding the world around him: he clicked with his mouth and listened for the returning echoes. This method enabled Ben to determine the locations of open doorways, people, parked cars, garbage cans, and so on. He was echolocating: bouncing his sound waves off objects in the environment and catching the reflections to build a mental model of his surroundings.

Echolocation may sound like an improbable feat for a human, but thousands of blind people have perfected this skill, just like Ben did. The phenomenon has been written about since at least the 1940s, when the word “echolocation” was first coined in a Science article titled “Echolocation by Blind Men, Bats, and Radar.”

How could blindness give rise to the stunning ability to understand the surroundings with one’s ears? The answer lies in a gift bestowed on the brain by evolution: tremendous adaptability.

Whenever we learn something new, pick up a new skill, or modify our habits, the physical structure of our brain changes. Neurons, the cells responsible for rapidly processing information in the brain, are interconnected by the thousands—but like friendships in a community, the connections between them constantly change: strengthening, weakening, and finding new partners. The field of neuroscience calls this phenomenon “brain plasticity,” referring to the ability of the brain, like plastic, to assume new shapes and hold them. More recent discoveries in neuroscience suggest that the brain’s brand of flexibility is far more nuanced than holding onto a shape, though. To capture this, we refer to the brain’s plasticity as “livewiring” to spotlight how this vast system of 86 billion neurons and 0.2 quadrillion connections rewires itself every moment of your life.

Neuroscience used to think that different parts of the brain were predetermined to perform specific functions. But more recent discoveries have upended the old paradigm. One part of the brain may initially be assigned a specific task; for instance, the back of our brain is called the “visual cortex” because it usually handles sight. But that territory can be reassigned to a different task. There is nothing special about neurons in the visual cortex: they are simply neurons that happen to be involved in processing shapes or colors in people who have functioning eyes. But in the sightless, these same neurons can rewire themselves to process other types of information.

Mother Nature imbued our brains with flexibility to adapt to circumstances. Just as sharp teeth and fast legs are useful for survival, so is the brain’s ability to reconfigure. The brain’s livewiring allows for learning, memory, and the ability to develop new skills.

In Ben’s case, his brain’s flexible wiring repurposed his visual cortex for processing sound. As a result, Ben had more neurons available to deal with auditory information, and this increased processing power allowed Ben to interpret soundwaves in shocking detail. Ben’s super-hearing demonstrates a more general rule: the more brain territory a particular sense has, the better it performs.

Recent decades have yielded several revelations about livewiring, but perhaps the biggest surprise is its rapidity. Brain circuits reorganize not only in the newly blind, but also in the sighted who have temporary blindness. In one study, sighted participants intensively learned how to read Braille. Half the participants were blindfolded throughout the experience. At the end of the five days, the participants who wore blindfolds could distinguish subtle differences between Braille characters much better than the participants who didn’t wear blindfolds. Even more remarkably, the blindfolded participants showed activation in visual brain regions in response to touch and sound. When activity in the visual cortex was temporarily disrupted, the Braille-reading advantage of the blindfolded participants went away. In other words, the blindfolded participants performed better on the touch-related task because their visual cortex had been recruited to help. After the blindfold was removed, the visual cortex returned to normal within a day, no longer responding to touch and sound.

But such changes don’t have to take five days; that just happened to be when the measurement took place. When blindfolded participants are continuously measured, touch-related activity shows up in the visual cortex in about an hour.

What does brain flexibility and rapid cortical takeover have to do with dreaming? Perhaps more than previously thought. Ben clearly benefited from the redistribution of his visual cortex to other senses because he had permanently lost his eyes, but what about the participants in the blindfold experiments? If our loss of a sense is only temporary, then the rapid conquest of brain territory may not be so helpful.

And this, we propose, is why we dream.

In the ceaseless competition for brain territory, the visual system has a unique problem: due to the planet’s rotation, all animals are cast into darkness for an average of 12 out of every 24 hours. (Of course, this refers to the vast majority of evolutionary time, not to our present electrified world.) Our ancestors effectively were unwitting participants in the blindfold experiment, every night of their entire lives.

So how did the visual cortex of our ancestors’ brains defend its territory, in the absence of input from the eyes?

We suggest that the brain preserves the territory of the visual cortex by keeping it active at night. In our “defensive activation theory,” dream sleep exists to keep neurons in the visual cortex active, thereby combating a takeover by the neighboring senses. In this view, dreams are primarily visual precisely because this is the only sense that is disadvantaged by darkness. Thus, only the visual cortex is vulnerable in a way that warrants internally-generated activity to preserve its territory.

In humans, sleep is punctuated by rapid eye movement (REM) sleep every 90 minutes. This is when most dreaming occurs . (Although some forms of dreaming can occur during non-REM sleep, such dreams are abstract and lack the visual vividness of REM dreams.)

REM sleep is triggered by a specialized set of neurons that pump activity straight into the brain’s visual cortex, causing us to experience vision even though our eyes are closed. This activity in the visual cortex is presumably why dreams are pictorial and filmic. (The dream-stoking circuitry also paralyzes your muscles during REM sleep so that your brain can simulate a visual experience without moving the body at the same time.) The anatomical precision of these circuits suggests that dream sleep is biologically important—such precise and universal circuitry rarely evolves without an important function behind it.

The defensive activation theory makes some clear predictions about dreaming. For example, because brain flexibility diminishes with age, the fraction of sleep spent in REM should also decrease across the lifespan. And that’s exactly what happens: in humans, REM accounts for half of an infant’s sleep time, but the percentage decreases steadily to about 18% in the elderly. REM sleep appears to become less necessary as the brain becomes less flexible.

Of course, this relationship is not sufficient to prove the defensive activation theory. To test it on a deeper level, we broadened our investigation to animals other than humans. The defensive activation theory makes a specific prediction: the more flexible an animal’s brain, the more REM sleep it should have to defend its visual system during sleep. To this end, we examined the extent to which the brains of 25 species of primates are “pre-programmed” versus flexible at birth. How might we measure this? We looked at the time it takes animals of each species to develop. How long do they take to wean from their mothers? How quickly do they learn to walk? How many years until they reach adolescence? The more rapid an animal’s development, the more pre-programmed (that is, less flexible) the brain.

As predicted, we found that species with more flexible brains spend more time in REM sleep each night. Although these two measures—brain flexibility and REM sleep—would seem at first to be unrelated, they are in fact linked.

As a side note, two of the primate species we looked at were nocturnal. But this does not change the hypothesis: whenever an animal sleeps, whether at night or during the day, the visual cortex is at risk of takeover by the other senses. Nocturnal primates, equipped with strong night vision, employ their vision throughout the night as they seek food and avoid predation. When they subsequently sleep during the day, their closed eyes allow no visual input, and thus, their visual cortex requires defense.

Dream circuitry is so fundamentally important that it is found even in people who are born blind. However, those who are born blind (or who become blind early in life) don’t experience visual imagery in their dreams; instead, they have other sensory experiences, such as feeling their way around a rearranged living room or hearing strange dogs barking. This is because other senses have taken over their visual cortex. In other words, blind and sighted people alike experience activity in the same region of their brain during dreams; they differ only in the senses that are processed there. Interestingly, people who become blind after the age of seven have more visual content in their dreams than those who become blind at younger ages. This, too, is consistent with the defensive activation theory: brains become less flexible as we age, so if one loses sight at an older age, the non-visual senses cannot fully conquer the visual cortex.

If dreams are visual hallucinations triggered by a lack of visual input, we might expect to find similar visual hallucinations in people who are slowly deprived of visual input while awake. In fact, this is precisely what happens in people with eye degeneration, patients confined to a tank-respirator, and prisoners in solitary confinement. In all of these cases, people see things that are not there.

We developed our defensive activation theory to explain visual hallucinations during extended periods of darkness, but it may represent a more general principle: the brain has evolved specific circuitry to generate activity that compensates for periods of deprivation. This might occur in several scenarios: when deprivation is regular and predictable (e.g., dreams during sleep), when there is damage to the sensory input pathway (e.g., tinnitus or phantom limb syndrome), and when deprivation is unpredictable (e.g., hallucinations induced by sensory deprivation). In this sense, hallucinations during deprivation may in fact be a feature of the system rather than a bug.

We’re now pursuing a systematic comparison between a variety of species across the animal kingdom. So far, the evidence has been encouraging. Some mammals are born immature, unable to regulate their own temperature, acquire food, or defend themselves (think kittens, puppies, and ferrets). Others are born mature, emerging from the womb with teeth, fur, open eyes, and the abilities to regulate their temperature, walk within an hour of birth, and eat solid food (think guinea pigs, sheep, and giraffes). The immature animals have up to 8 times more REM sleep than those born mature. Why? Because when a newborn brain is highly flexible, the system requires more effort to defend the visual system during sleep.

Since the dawn of communication, dreams have perplexed philosophers, priests, and poets. What do dreams mean ? Do they portend the future? In recent decades, dreams have come under the gaze of neuroscientists as one of the field’s central unsolved mysteries. Do they serve a more practical, functional purpose? We suggest that dream sleep exists, at least in part, to prevent the other senses from taking over the brain’s visual cortex when it goes unused. Dreams are the counterbalance against too much flexibility. Thus, although dreams have long been the subject of song and story, they may be better understood as the strange lovechild of brain plasticity and the rotation of the planet.

For more information:

• Eagleman DM (2020). Livewired: The Inside Story of the Ever-Changing Brain. New York: Pantheon.
• Eagleman DM, Vaughn DA (2020). The defensive activation theory: dreaming as a mechanism to prevent takeover of the visual cortex .

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Science News

Here’s what lucid dreamers might tell us about our sleeping minds.

Dreams are one of the most universal yet elusive human experiences

Most people rarely lucid dream. But some people can do it regularly and even gain control over these alternate realities.

RUNE FISKER

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By Maria Temming

August 27, 2023 at 9:00 am

When Christopher Mazurek realizes he’s dreaming, it’s always the small stuff that tips him off.

The first time it happened, Mazurek was a freshman at Northwestern University in Evanston, Ill. In the dream, he found himself in a campus dining hall. It was winter, but Mazurek wasn’t wearing his favorite coat.

“I realized that, OK, if I don’t have the coat, I must be dreaming,” Mazurek says. That epiphany rocked the dream like an earthquake. “Gravity shifted, and I was flung down a hallway that seemed to go on for miles,” he says. “My left arm disappeared, and then I woke up.”

Most people rarely if ever realize that they’re dreaming while it’s happening, what’s known as lucid dreaming. But some enthusiasts have cultivated techniques to become self-aware in their sleep and even wrest some control over their dream selves and settings. Mazurek, 24, says that he’s gotten better at molding his lucid dreams since that first whirlwind experience, sometimes taking them as opportunities to try flying or say hi to deceased family members.

Other lucid dreamers have used their personal virtual realities to plumb their subconscious minds for insights or feast on junk food without real-world consequences. But now, scientists have a new job for lucid dreamers: to explore their dreamscapes and report out in real time.

Dream research has traditionally relied on reports collected after someone wakes up. But people often wake with only spotty, distorted memories of what they dreamed. The dreamers can’t say exactly when events occurred, and they certainly can’t tailor their dreams to specific scientific studies.

Gravity shifted, and I was flung down a hallway that seemed to go on for miles.… My left arm disappeared, and then I woke up. Christopher Mazurek

“The special thing about lucid dreaming is that you can get even closer to dream content and in a much more controlled and systematic fashion,” says Martin Dresler, a cognitive neuroscientist at the Donders Institute in Nijmegen, Netherlands.

Lucid dreamers who can perform assigned tasks and communicate with researchers during a dream open up tantalizing opportunities to study an otherwise untouchable realm. They are like the astronauts of the dream world, serving as envoys to the mysterious inner spaces created by slumbering minds.

So far, tests in very small groups of lucid dreamers suggest that the strange realities we visit in sleep may be experienced more like the real world than imagined ones. With more emissaries enlisted, researchers hope to probe how sleeping brains construct their elaborate, often bizarre plots and set pieces. Besides satisfying age-old curiosity, this work may point to new ways to treat nightmares. Lucid dream studies could also offer clues about how dreams contribute to creativity, regulating emotions or other cognitive jobs — helping solve the grand mystery of why we dream.

But there are still a lot of problems to solve before lucid dreaming research can really take off. Chief among them is that very few dreamers can become lucid on demand in the lab. Those who can often struggle to do scientists’ bidding or communicate with the waking world. Pinpointing the best techniques to give more people more lucid dreams may assuage those issues. But even if it does, not all scientists agree on what lucid dreams can tell us about the far more common, nonlucid kind.

Are lucid dreams real?

Tales of lucid dreams date back to antiquity. Aristotle may have been the first to mention them in Western literature in his treatise On Dreams . “Often when one is asleep,” he wrote, “there is something in consciousness which declares that what then presents itself is but a dream.”

If Aristotle had lucid dreams often, though, he was probably an outlier. Only about half of people say they’ve ever had a lucid dream , while a mere 1 percent or so say they lucid dream multiple times a week. Modern enthusiasts use various techniques to boost their likelihood of lucid dreaming — such as repeatedly telling themselves before bedtime that they will have a lucid dream, or making a habit of checking whether they’re awake several times a day in the hopes that this routine carries over into their dreams, where a self-check may help them realize they’re asleep. But those practices don’t guarantee lucidity.

The rarity of lucid dreaming may be why modern science took some convincing that it’s even real. For millennia, lucid dreamers’ own testimonies were the only evidence that someone could be self-aware while catching z’s. Some scientists wondered if so-called lucid dreams were just brief waking hallucinations between bouts of sleep.

But within the last few decades, experiments have offered proof that lucid dreams are truly what they seem. It turns out, when someone in a dream purposely sweeps their gaze all the way left, then all the way right, their eyes can match those movements behind closed lids in real life. These motions, measured by electrodes near the eyes, stand out from the smaller optical jitters typical of REM sleep, when most lucid dreams happen. This gives dreamers a crude way to signal they’ve become lucid or send other messages to the outside world ( SN: 9/19/81, p. 183 ). Meanwhile, brain waves and muscle paralysis throughout the rest of the body confirm that the dreamer is indeed asleep.

Eyes on eye movements

A person’s eyes can smoothly track left and right movements when they are awake or in a lucid dream. But when someone closes their eyes and tries to imagine tracking that motion, their eyes pan in small jumps, suggesting that lucid dreams are experienced more like waking perception.

Neuroscientists are just beginning to realize the potential of that line of communication. Lucid dream research “has been enjoying a renaissance over the last decade,” says neuroscientist Tore Nielsen. He directs the Dream & Nightmare Laboratory at the Center for Advanced Research in Sleep Medicine in Montreal. “This renaissance has made it one of the cutting-edge areas of dream study.”

One research team recently deployed experienced lucid dreamers to find out whether dream imagery is more like real-life visuals or imagined ones. While asleep, six lucid dreamers moved their thumbs in either a circle or a line (or both) and traced that motion with their eyes. Participants repeated the same task while awake with their eyes open and in their imaginations with their eyes closed. People’s gazes panned jerkily when they tracked the imagined movements, as though they were viewing something in low resolution. But in dreams, people’s eyes tracked the movements smoothly just as in real life, the team reported in 2018 in Nature Communications .

“It’s been debated really all the way back to the ancient Greeks, are dreams more like imagination, or is it more like perception?” says study coauthor Benjamin Baird, a cognitive psychologist and neuroscientist at the University of Texas at Austin. “The smooth tracking data suggests that, at least in that sense, the imagery is more like perception.”

This and other early experiments offer a taste of what dreamstronauts could teach us. But any conclusions based on just a handful of dreamers have to be taken with a grain of salt. “They’re more like proof-of-concept studies,” says Michelle Carr, a cognitive neuroscientist at the Center for Advanced Research in Sleep Medicine. “It needs to be studied in bigger samples.”

That means finding — or creating — more expert lucid dreamers.

Strategies for lucid dreaming

If you want to have a lucid dream, there are a few strategies you can use to up your chances. Besides regularly questioning whether you’re awake and setting an intention before bed to become lucid, you can keep a dream diary. Getting familiar with common characters, events or themes in your dreams may help you recognize when you’re dreaming. Some aspiring lucid dreamers also use a tactic called “wake-back-to-bed.” They wake up extremely early in the morning, stay up for a while, then get more shut-eye. That jolt of alertness right before tumbling back into REM sleep may help them become lucid in a dream.

Such techniques can be hit-or-miss, though. And data on their effectiveness are still pretty murky, Baird says. One study with about 170 Australians, for instance, suggested that checking if you’re awake, setting an intention to become lucid and doing wake-back-to-bed all together can increase your odds of lucid dreaming . But it wasn’t as clear if using just one or two of those practices worked.

Investigations by Baird and others have shown that the supplement galantamine promotes lucid dreaming , probably by fiddling with neurotransmitters involved in REM sleep. But galantamine can be saddled with side effects such as nausea. And although lucidity itself does not appear to spoil sleep quality , the long-term effects of using galantamine are not well-known. “Personally, I wouldn’t be mucking around with my neurotransmitters every night,” Baird says.

In 2020, Carr and colleagues reported that they’d coaxed 14 of 28 nappers to become lucid in the lab — including three people who’d never before lucid dreamed — no drugs necessary. Before falling asleep, participants learned to associate a cue, such as a series of beeps, with self-awareness. Hearing the same sound again while sleeping reminded them to become lucid. Carr is particularly interested in finding out whether lucid dreaming can help people conquer nightmares, but researchers at Northwestern use the sensory cue strategy to get more lucid emissaries to carry out dream tasks for their experiments.

Galantamine as a dream aid

For three nights, 121 people combined commonly used strategies for lucid dreaming with one of three doses of galantamine. Those who took higher doses of galantamine were more likely to have lucid dreams.

Effect of galantamine dose on likelihood of lucid dreaming

“Our method is kind of a shortcut,” says Northwestern cognitive neuroscientist Ken Paller. It doesn’t require a lot of mental training or the grueling sleep interruptions that some other lucid dreaming techniques do.

Another shortcut for researchers is to recruit dreamers from a special slice of the population: people with narcolepsy, who are liable to fall asleep suddenly during the day.

“They’re just champions at lucid dreams,” says Isabelle Arnulf, a sleep neurologist who heads the sleep disorders clinic at Pitie-Salpetriere University Hospital in Paris.

In 2018, Arnulf’s team reported a study where 18 of 21 narcolepsy patients signaled lucidity during lab naps . Even with those impressive numbers, a couple of lucid nappers still couldn’t control their dreams well enough to complete their assignment: to do something in a dream that made them briefly stop breathing, such as swimming underwater or speaking. One said after waking that they’d simply forgotten to stop breathing while diving off a cliff, while another said they tried to speak but couldn’t get any words out.

Staying lucid and successfully wrangling dream scenarios present challenges for lucid dreamers — and the scientists relying on them. In one study, lucid dreamers instructed to fill a dream room with objects, such as a clock and a rubber snake, ran into problems ; the clock spun wildly, or the snake slithered away. In another experiment, lucid dreamers asked to practice throwing darts were waylaid by only having pencils to throw or being pelted with darts by a nasty doll.

“It’s a lot harder than just passively lucid dreaming in your bed,” says Mazurek, who has participated in several lucid dream studies at Northwestern. “You realize, ‘OK, I have to stabilize the dream. I have to remember what the task is. I have to do the task without the dream falling apart.’ ”

Missions to the moon may be hard, but at least astronauts don’t have to worry about forgetting who or where they are, or their spaceship suddenly turning into a banana.

Despite these challenges, lucid dream expeditions are forging ahead — and fast. In fact, an international crew of dreamfarers, including Mazurek, recently embarked on their most ambitious mission yet.

Real-time dream science

When it comes to getting on-the-ground data, interviewing dreamers in real time is, well, the dream. Instead of just sitting back and watching dreamers do various activities, researchers could ask these agents about their experiences moment to moment, painting the realm of dreams in sharper detail than ever before.

“Reports of dreamed sensations, [such as] tasting certain foods, can be compared with those of actual sensations,” Nielsen says. “Similarly, one could test whether sexual pleasure, certain sounds or other types of experiences are accurately simulated.” These details, he says, might help “probe the limits and mechanisms of dream production.”

Karen Konkoly is especially excited about giving people assignments mid-dream. Say researchers want to know how much dreams help with creative problem-solving. If dreamers are assigned a problem before sleep, they’re liable to mull it over as they nod off. “Even if it feels like the lucid dream, maybe it’s really the time as you’re falling asleep that helped you solve the problem,” says Konkoly, a cognitive neuroscientist at Northwestern. Airdropping a puzzle straight into a dream could better isolate the usefulness of that specific part of sleep.

There’s a whole medley of theories about why people dream, from honing skills to tapping into creativity to processing memories or emotions. “But if you can’t control the dream in real time and then study the outcome, then you never know … if the dream is really doing anything,” Konkoly says. So a few years ago, she, Arnulf, Dresler and others decided to find out if people can receive and respond to outside input while dreaming.

Thirty-six people took snoozes at Northwestern, Arnulf’s lab, Dresler’s lab or another lab that was in Germany. Once sleepers signaled that they were lucid, researchers spoke yes-or-no questions or math problems in the sleepers’ ears. Or, for the Germans, lights flashing different colors conveyed math questions in Morse code. Before conking out, dreamers were told to answer whatever questions they received with eye signals or by smiling and frowning.

“Facial muscles are less inhibited than other muscles during REM sleep,” Arnulf explains. Someone smiling in a dream may not make that expression in real life, but electrodes on the face can register tiny corresponding muscle twitches.

Out of 158 attempts to interrogate lucid dreamers, 29 total correct responses came from six different people . Those six ranged from newbie to frequent lucid dreamers, including Mazurek, who heard scientists’ questions while dreaming he was in a Legend of Zelda game. The rest of the attempts yielded five wrong answers, 28 ambiguous ones and 96 nonresponses.

When Konkoly first saw someone correctly answer a question in their sleep, “my first reaction was to not believe it.” But for 26 of those 29 correct responses, a panel of independent sleep experts unanimously agreed that the dreamers were in the throes of REM sleep when they replied. Nearly 400 attempts to reach sleepers who hadn’t signaled lucidity netted a single correct response — bolstering the researchers’ confidence that correct answers from lucid dreamers weren’t flukes. The results appeared in 2021 in Current Biology .

Answering questions during a dream

While dreaming, Christopher Mazurek signaled the outside world by sweeping his eyes left and right. Electrodes on his face recorded those motions. On the graph below, Mazurek’s eye motions that indicate he is lucid appear as three big up-down sweeps. Eye signals answering “2” to researchers’ simple math question appear as two big up-down sweeps.

Lucid dreamer’s eye movements during a mid-dream conversation

“I was astonished,” says Robert Stickgold, a cognitive neuroscientist at Harvard Medical School who studies dreams but not lucid ones. “I had no question but that these people are in fact listening and are in fact having lucid dreams at the time of the communication — and that opens up all sorts of possibilities.”

Arnulf and others have since asked lucid dreamers to smile or frown as their dreams became more or less pleasant with the goal of understanding how dreamers experience emotion. Another study, not yet published, tracked when lucid dreamers answered or ignored researchers’ questions to see how people tuned in and out of the real world while dreaming. Knowing which signals break the dream-reality barrier could help “uncover the mechanism of the brain’s disconnection from the external world — which is huge,” Baird says. It could even be relevant for other states of unconsciousness, he adds, such as when someone is put under for surgery.

Limits of lucidity

Even if researchers get all the expert lucid dreamers they need to run all their desired experiments, there’s still one major sticking point to this whole field of study.

“The biggest issue is how far can you push these results to dreaming in general,” Stickgold says. Imagine, for instance, that lucid dreamers get better at a skill by practicing it in their dreams. It’s not clear that people who just happen to have normal dreams about doing those activities, without self-awareness, would reap the same rewards. “It’s a little bit like recruiting major league baseball players to give you some baseline data on how far people can throw balls,” Stickgold says.

Existing data do suggest that lucid dreamers may have access to parts of the brain that normal dreamers don’t. The lone case study comparing fMRIs of someone’s lucid and nonlucid REM sleep hints that brain areas linked with self-reflection and working memory are more active during lucidity. But those data come from just one person, and it’s not yet clear how such differences in brain activity would affect the outcomes of lucid dream experiments.

Brain clues to lucid dreams

Functional MRI scans of one sleeper’s brain during lucid and nonlucid sleep showed that some brain areas (highlighted) may be more active during lucid dreams than during normal sleep.

• The lateral parietal cortex is involved in working memory.
• The dorsolateral prefrontal cortex and frontopolar cortex are involved in working memory and introspection.
• Activity near the temporal cortex may make lucid dreams brighter and more detailed than normal dreams.

Some researchers, including Dresler, resist the idea that lucid dreams are profoundly different from nonlucid ones. “Lucid dreaming is not a strict all-or-nothing phenomenon,” he says, with people often fluttering in and out of awareness. “That suggests that lucid and nonlucid dreaming are in principle something very similar on the neural level and not two completely different animals.”

Perhaps lucidity affects some aspects of the dream experience but not all of them, Baird adds. In terms of how dreams look, he says, “it would be very, very surprising if it was somehow completely different when you become lucid.”

A more thorough inventory of the differences in brain activity between lucid and nonlucid dreams might help settle these questions. But even if lucid dreams don’t represent dreams in general, Nielsen still thinks they’re worth studying. “It is a type of consciousness that has intrigued and amused people for centuries,” he says. “It would be important for science to understand how and why humans have this extraordinary capacity for intentional world simulation.”

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REVIEW article

Experimental research on dreaming: state of the art and neuropsychoanalytic perspectives.

• 1 INSERM U1028, Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, Lyon, France
• 2 CNRS UMR5292, Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, Lyon, France
• 3 University Lyon 1, Lyon, France

Dreaming is still a mystery of human cognition, although it has been studied experimentally for more than a century. Experimental psychology first investigated dream content and frequency. The neuroscientific approach to dreaming arose at the end of the 1950s and soon proposed a physiological substrate of dreaming: rapid eye movement sleep. Fifty years later, this hypothesis was challenged because it could not explain all of the characteristics of dream reports. Therefore, the neurophysiological correlates of dreaming are still unclear, and many questions remain unresolved. Do the representations that constitute the dream emerge randomly from the brain, or do they surface according to certain parameters? Is the organization of the dream’s representations chaotic or is it determined by rules? Does dreaming have a meaning? What is/are the function(s) of dreaming? Psychoanalysis provides hypotheses to address these questions. Until now, these hypotheses have received minimal attention in cognitive neuroscience, but the recent development of neuropsychoanalysis brings new hopes of interaction between the two fields. Considering the psychoanalytical perspective in cognitive neuroscience would provide new directions and leads for dream research and would help to achieve a comprehensive understanding of dreaming. Notably, several subjective issues at the core of the psychoanalytic approach, such as the concept of personal meaning, the concept of unconscious episodic memory and the subject’s history, are not addressed or considered in cognitive neuroscience. This paper argues that the focus on singularity and personal meaning in psychoanalysis is needed to successfully address these issues in cognitive neuroscience and to progress in the understanding of dreaming and the psyche.

The word “dream” is commonly used to express an unattainable ideal or a very deep and strong desire:

I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin, but by the content of their character.

Martin Luther King

In dream reports, however, one often notices banal situations, strange scenes, or even frightening events. Why is there such a contrast between the popular meaning of the word “dream” and the content of dream reports? Why are some dream scenes so bizarre? Are dreams built from images that arise randomly from the sleeping brain? Or is the emergence and organization of dream images controlled by currently unknown parameters? Does dreaming have a function?

Answering these questions is not easy because dreaming is elusive. We still do not know when it happens during the night, how long it lasts, whether we can recall its entire content, or how to control it. For more than a century, such limited understanding of dreaming has seriously hampered experimental investigations. Nonetheless, scientific research has managed to produce considerable information about the phenomenology and physiology of dreaming and has improved our understanding of this fascinating phenomenon.

Experimental Research on Dreaming

Dreaming and experimental psychology, dream content.

Dreaming was first investigated on an experimental level in the nineteenth century. Calkins (1893) published the first statistical results about dreaming and argued that some aspects of dream content could be quantified. Later, questionnaires and automatic analysis of the lexical content of dream reports allowed psychologists to show that dream content has some precise phenomenological characteristics. According to psychological studies ( Hall and Van de Castle, 1966 ; Schwartz, 1999 ), visual imagery occurs more frequently in dreams than imagery of other senses (audition, olfaction, touch, and taste); the dream drama is mostly lived by the dreamer from a first-person perspective; some elements of real-life events previously experienced by the dreamer often contribute to the scene of the dream; most often, the dream sequence is not within the dreamer’s voluntary control (i.e., the dreamer may be convinced during the dream that the dream’s story is really happening); temporal and spatial incoherencies can occur in the dream story; the dream report is often full of people interacting with each other (e.g., discussions, fights, pursuit, sexuality); and finally, the dream report often contains strong emotions.

Substantial variability of content exists, however, among the same individual’s dreams and among the dreams of different individuals. Further, psychological studies have shown that many internal and external parameters can influence dream content. For example, males report more aggression and violence in their dreams than do females ( Nielsen et al., 2003 ; Schredl et al., 2004 ). External stimulation perceived by the dreamer can be incorporated into dreams ( Koulack, 1969 ; Saint-Denys, 1867; Hoelscher et al., 1981 ), as illustrated by the famous Dali painting Dream Caused by the Flight of a Bee around a Pomegranate a Second before Awakening . The current concerns of the subject may also be found in the content of his/her dreams ( Schwartz, 1999 ; Domhoff and Schneider, 2008 ), and many aspects of the subject’s daily life were found to influence dream content, including news events ( Bulkeley and Kahan, 2008 ), musical practice ( Uga et al., 2006 ), religious beliefs ( Domhoff and Schneider, 2008 ), chronic pain ( Raymond et al., 2002 ), mood ( Cartwright et al., 1998a ), or a violent living environment ( Valli et al., 2005 ). By contrast, congenital or acquired malformations do not seem to significantly influence dream content ( Voss et al., 2010 ; Saurat et al., 2011 ).

Based on these results, two opposing hypotheses were formulated: the continuity hypothesis ( Schredl and Hofmann, 2003 ) and the discontinuity hypothesis ( Rechtschaffen, 1978 ; Kahn et al., 1997 ; Stickgold et al., 2001 ). The former relies on results showing that the themes of an individual’s thoughts during waking life and dreaming are similar; the latter focuses on the fundamentally different structures of thoughts during waking life and dreaming. Voss et al. (2010) stressed in their recent paper that these hypotheses represent oversimplified approaches to dream analysis and argued that waking and dreaming thoughts were related but structurally independent; in other words, she argued in favor of merging the continuity and discontinuity hypotheses.

Dream report frequency

Dream report frequency (DRF) can vary within subjects and varies substantially among subjects. In a study of 900 German subjects with a large age range from various socioprofessional categories, the mean DRF was approximately 1 dream report per week ( Schredl, 2008 ). This result shows that the dream experience is common and familiar to everyone. Psychological studies have demonstrated that many parameters covary with DRF and may thus influence it.

Sleep parameters. First, DRF varies according to the sleep stage preceding awakening (e.g., Dement and Kleitman, 1957b ; Nielsen, 2000 , for a review). More dream reports are obtained after an awakening during rapid eye movement (REM) sleep than after an awakening during non-REM (NREM) sleep. These results inspired the REM sleep hypothesis of dreaming (see the section Dreaming and Neuroscience). Second, DRF increases with the number of awakenings during sleep, according to retrospective self-evaluations of awakenings ( Cory and Ormiston, 1975 ; Schredl et al., 2003 ). Such studies showed that the more the subjects tended to awaken during sleep, the higher their DRF. These results support the hypothesis of Koulack and Goodenough (1976) , which proposes that nocturnal awakenings facilitate the encoding of the dream in memory and thus facilitate dream recall upon awakening. However, this hypothesis has not been tested by measuring awakenings with polysomnographic recordings in healthy subjects with various DRFs. Finally, DRF varies according to the method of awakening. Abrupt awakenings lead to more dream reports than gradual awakenings ( Shapiro et al., 1963 , 1965 ; Goodenough et al., 1965 ).

Physiological and environmental parameters. Dream report frequency deceases with age (e.g., Schredl, 2008 ) and tends to be slightly higher among females than males (e.g., Schredl, 2008 ; Schredl and Reinhard, 2008 ). Remarkably, Schredl’s (2008) results revealed that DRF also varied according to the size of the subject’s place of residence.

Psychological parameters. First, increased professional stress or interpersonal stress resulted in an increase in DRF (for a review, see Schredl, 1999 ). Second, an interest in dreams or a positive attitude toward dreams clearly covaries with DRF ( Hill et al., 1997 ; Schredl, 1999 ; Schredl et al., 2003 ). The greater an individual’s interest in dreams, the higher his/her DRF. Third, several cognitive abilities have been found to covary with DRF. Contradictory results have been reported for the correlation between DRF and memory abilities (short-term, long-term, visual, verbal, implicit, and explicit; significant positive correlation: Cory and Ormiston, 1975 ; Belicki et al., 1978 ; Butler and Watson, 1985 ; Schredl et al., 1995 ; Solms, 1997 ; no significant correlation: Cohen, 1971 ; Belicki et al., 1978 ; Schredl et al., 1995 , 1997 , 2003 ; Solms, 1997 ) and the correlation between DRF and visual imagery ( significant positive correlation : Hiscock and Cohen, 1973 ; Richardson, 1979 ; Okada et al., 2000 ; no significant correlation : Hill et al., 1997 ; Okada et al., 2000 ). However, several studies have consistently shown that DRF is positively correlated with creativity ( Fitch and Armitage, 1989 ; Schredl, 1999 ; Schredl et al., 2003 ) and intelligence scales (multiple-choice vocabulary test, Schonbar, 1959 ; Shipley Intelligence Scale, Connor and Boblitt, 1970 ). Finally, many authors have reported a correlation between DRF and personality traits. Subjects with a high DRF are more likely to have a personality with thinner boundaries (Hartmann described people with thin boundaries as being open, trustworthy, vulnerable, and sensitive; Hartmann, 1989 ; Hartmann et al., 1991 ; Schredl et al., 2003 ), to be more anxious ( Schonbar, 1959 ; Tart, 1962 ), to have a higher level of absorption (the absorption scale measures the capacity to become absorptively involved in imaginative and esthetic experiences; Hill et al., 1997 ; Schredl, 1999 ; Schredl et al., 2003 ), to be more open to experience ( Hill et al., 1997 ; Schredl et al., 2003 ), and to be less alexithymic (alexithymia is a personality variable that incorporates difficulty identifying and describing feelings, difficulty distinguishing between feelings and the physical sensation of emotional arousal, limited imaginative processes, and an externally oriented cognitive style; De Gennaro et al., 2003 ; Nielsen et al., 2011 ) compared to subjects with a low dream recall frequency. However, those results have not always been reproducible (e.g., Schredl, 2002 for openness to experience; Cory and Ormiston, 1975 ; Hill et al., 1997 for anxiety; Nielsen et al., 1997 for alexithymia) and, according to the recent review by Blagrove and Pace-Schott (2010) , it is difficult to draw conclusions about a possible link between personality traits and DRF.

In conclusion, numerous parameters have been identified that covary with DRF. Schredl stressed in many of his papers that the studied parameters usually explain only a small percentage of the total variance (e.g., Schredl, 2008 ). Thus, the DRF variation profile suggests that the production, encoding and recall of dreams are influenced by numerous parameters that probably interact with each other.

Dreaming and Neuroscience

The neuroscientific approach to dreaming arose at the end of the 1950s with the discovery of REM during human sleep by the American physiologist Nathaniel Kleitman and his team ( Aserinsky and Kleitman, 1953 ; Dement and Kleitman, 1957a ). During these sleep episodes with saccades, the researchers noticed a decrease in voltage and an increase in frequency in the EEG, accompanied by an increase in cardiac frequency variability and a decrease in body movements. They concluded that these physiological modifications indicate a particular sleep stage, which they called REM sleep. A few years later, the French team led by neurobiologist Michel Jouvet discovered that the lack of movement during REM sleep in cats was due to a general muscular atonia, controlled notably by the locus coeruleus α in the brainstem ( Jouvet and Michel, 1959 ; Berger, 1961 later showed that muscular atonia during REM sleep also occurs in humans). Interestingly, the inability to move during REM sleep indicates deep sleep and paradoxically, the fast EEG activity of REM sleep resembles EEG activity in wakefulness. Jouvet concluded that this particular physiological state is associated with a “third state” of the brain (in addition to the brain states associated with wakefulness and NREM sleep) which he called “paradoxical sleep” instead of “REM sleep” ( Jouvet et al., 1959 ; Jouvet, 1992 ). Several years later, Fisher et al. (1965) discovered another physiological characteristic of REM sleep: the penile erection.

During the same period, the American team noticed that a subject awakened during REM sleep very often reported a dream (80% of awakenings in REM sleep vs. 6% of awakenings in NREM sleep are followed by a dream report, according to Dement and Kleitman, 1957b ). Researchers concluded that dreaming occurs during REM sleep. The eye movements of REM sleep would allow the dreamer to scan the imaginary scene of the dream (the scanning hypothesis); the cerebral cortex activation revealed by the rapid EEG would allow intense cognitive activity, creating the complex stories of a dream; and the lack of muscle tone would prevent the dreamer from acting out his dreams. From that time on, researchers investigated REM sleep to obtain answers about dreaming.

In the 1990s, researchers used functional neuroimaging techniques such as positron emission tomography (PET) to investigate brain activity during REM sleep in humans. This new approach enabled researchers to demonstrate that the functional organization of the brain during REM sleep is different from the functional organization of the brain during wakefulness ( Maquet et al., 1996 ; Braun et al., 1998 ). In comparison to wakefulness, brain activity during REM sleep is decreased in some brain regions (e.g., in the dorsolateral prefrontal cortex; Braun et al., 1998 ) and increased in other regions (e.g., in the occipital and temporal cortex, the hippocampus and parahippocampus, the anterior cingulate, the precentral and postcentral gyri, the superior parietal cortex, and the pons; Braun et al., 1998 ; Maquet et al., 2000 ). Looking more generally for brain activity correlating with REM sleep (the vigilance states considered included wakefulness, slow-wave sleep, and REM sleep), Maquet et al. (1996) found negative correlations in the precuneus, posterior cingulate cortex, temporoparietal junction, and dorsolateral prefrontal cortex and positive correlations in the amygdala, anterior cingulate, postcentral gyrus, thalamus, and pons (see Schwartz and Maquet, 2002 ; Maquet et al., 2005 ; Nir and Tononi, 2010 for reviews). Based on these results, researchers argued that the particular functional organization of the brain during REM sleep could explain the phenomenological characteristics of dream reports ( Hobson and Pace-Schott, 2002 ; Schwartz and Maquet, 2002 ; Maquet et al., 2005 ; Nir and Tononi, 2010 ). They considered that brain activity increases and decreases during REM sleep could be interpreted on the basis of what we know about brain activity during wakefulness. In this context, the increased occipital cortex activity during REM sleep could explain the visual component of dream reports because neuroimaging results during wakefulness showed that visual imagery with the eyes closed activates the occipital cortex ( Kosslyn and Thompson, 2003 ). The decreased activity in the temporoparietal junction during REM sleep may explain why dreams are mainly experienced in the egocentric coordinates of the first-person; indeed, during wakefulness, activity in the temporoparietal junction was reported to be greater for allocentric vs. egocentric representation (e.g., Ruby and Decety, 2001 ; Zacks et al., 2003 ) and for third- vs. first-person perspective (e.g., Ruby and Decety, 2003 , 2004 ). The increased activity in the hippocampus during REM sleep could explain why dreams are often composed of known images or characters, as the hippocampus is known to be associated with the encoding and retrieval of lived events during wakefulness (e.g., Piolino et al., 2009 ). The decreased activity in the lateral prefrontal cortex during REM sleep could explain why dream stories lack consistency, why the dreamer’s perception of time is altered, why the dream story is beyond the control of the dreamer and why the dreamer is convinced that the dream story is really happening. Indeed, during wakefulness, the lateral prefrontal cortex is involved in executive function, cognitive control, and working memory ( Petrides, 2005 ; Koechlin and Hyafil, 2007 ). The increased activity in the medial prefrontal cortex during REM sleep could explain the attribution of thoughts, beliefs, and emotions to the characters in the dream because, during wakefulness, the medial prefrontal cortex is known to participate in mind reading ( Ruby et al., 2007 , 2009 ; Legrand and Ruby, 2009 ). The increased activity in the motor cortex (precentral gyrus) during REM sleep could explain the movements of the characters’ bodies in the dream because, during wakefulness, motor imagery, and the imagination of someone’s action from the third-person perspective involve the precentral gyrus ( Decety et al., 1994 ; Ruby and Decety, 2001 ). Finally, the amygdala’s activity during REM sleep could explain why emotions, especially fear, are often mentioned in dream reports; indeed, the amygdala is involved in the processing of emotional stimuli during wakefulness ( Adolphs, 2008 ).

In conclusion, results from experimental psychology and neuroscience allow us to better understand the phenomenology of dreaming and the cerebral correlates of some characteristics of dream reports. Still, what do they tell us about the role of dreaming? What are the current hypotheses about dream function(s)?

Hypotheses about Dream Function(s)

No function.

At the end of the twentieth century, the neurologist Alan Hobson, who was profoundly anti-psychoanalysis, proposed a theory that deprived dreaming of any function. Hobson argued that dreaming is an epiphenomenon of REM sleep: “Because dreams are so difficult to remember, it seems unlikely that attention to their content could afford much in the way of high-priority survival value. Indeed, it might instead be assumed that dreaming is an epiphenomenon of REM sleep whose cognitive content is so ambiguous as to invite misleading or even erroneous interpretation” ( Hobson et al., 1998 ).

Psychological individualism

In contrast, other teams, like Michel Jouvet’s, believed that dreaming serves a vital function. In 1979, Jouvet’s team blocked muscular atonia during REM sleep in a cat by damaging the locus coeruleus α in its brainstem. This lesion resulted in the appearance of movements during REM sleep. Movies from the Jouvet lab show sleeping cats performing complex motor actions (with altered control and coordination) resembling those of wakefulness, such as fur licking, growling, chasing prey, mastication, and fighting. From these videos, the authors concluded that the cat was acting out its dream, and they called this non-physiological state “oneiric behavior” ( Sastre and Jouvet, 1979 ). These results led Jouvet to propose that dreaming plays a role in reinforcing a species’ typical behavior. Later in his career, Jouvet moved toward a hypothesis focusing on the role of dreaming in the individual dimension. He speculated that dreams (note that, for Jouvet, dreams and paradoxical sleep were equivalent) could be involved in psychological individualism and in the stability of the dreamer’s personality ( Jouvet, 1991 , 1992 , 1998 ). According to Jouvet, “the brain is the sole organ of homeotherms that do not undergo cell division. We thus have to explain how certain aspects of psychological heredity (found in homozygote twins raised in different surroundings) may persist for a whole life (psychological individuation). A definitive genetic programming during development (by neurogenesis) is unlikely due to the plasticity of the nervous system. That is why we have to consider the possibility of an iterative genetic programming. The internal mechanisms (synchronous) of paradoxical sleep (SP) are particularly adapted to such programming. This would activate an endogenous system of stimulation that would stimulate and stabilize receptors genetically programmed by DNA in some neuronal circuits. The excitation of these neurons during SP leads to oniric behaviors that could be experimentally revealed – the lists of these behaviors are specific to each individual and indirect data suggest a genetic component of this programming. Amongst the mechanisms allowing the iterative programming of SP, sleep is particularly important. Security – and hence the inhibition of the arousal system – is a sine qua non-condition for genetic programming to take place. In that sense, sleep could very well be the guardian of dreaming” ( Jouvet, 1991 ). In other words, Jouvet’s hypothesis is that paradoxical sleep restores neuronal circuitry that was modified during the day to preserve the expression of the genetic program that codes for psychological characteristics. This process would ensure the stability of personality across time.

The threat simulation theory

The Finnish psychologist Antti Revonsuo recently proposed a hypothesis called threat simulation theory, which explains the fearful characteristics of dream content ( Revonsuo, 2000 ; Valli and Revonsuo, 2009 ). According to this theory, dreams serve as virtual training places to improve threat avoidance or threat fighting ability. The theory postulates that such nocturnal training makes the dreamer more efficient at resolving threatening situations during wakefulness.

Emotional regulation

Cartwright et al. (1998a , b ) defended the idea that dreaming is involved in emotional regulation. Her team showed that, in healthy subjects, the depression level before sleep was significantly correlated with affect in the first REM report. Her team also observed that low scorers on the depression scale displayed a flat distribution of positive and negative affect in dreams, whereas those with a depressed mood before sleep showed a pattern of decreasing negative and increasing positive affect in dreams reported from successive REM periods ( Cartwright et al., 1998a ). These results led Cartwright’s team to suggest that dreaming may actively moderate mood overnight in normal subjects. The team strengthened this hypothesis by showing that among subjects who were depressed because of a divorce, those who reported more negative dreams at the beginning of sleep and fewer at the night’s end were more likely to be in remission 1 year later than subjects who had fewer negative dreams at the beginning of sleep and more at the end of the night ( Cartwright et al., 1998b ). The researchers concluded that negative dreams early in the night may reflect a within-sleep mood regulation process, whereas those that occur later may indicate a failure in the completion of this process.

Memory consolidation

Finally, a current mainstream hypothesis in cognitive neuroscience credits sleep and dreaming with a role in memory consolidation (for a recent review, see Diekelmann and Born, 2010 ). Numerous studies have shown that brain activity during training is replayed during post-training sleep (e.g., using a serial reaction time task Maquet et al., 2000 , demonstrated replay during REM sleep; using a maze exploration task Peigneux et al., 2004 , demonstrated replay during slow-wave sleep). Decreased performance during the post-training day in sleep-deprived subjects further suggested that the replay of brain activity at night contributes to memory consolidation (e.g., Maquet et al., 2003 ). Only recently, however, have experimental results in humans argued in favor of a role of dreaming per se in memory consolidation. In one study, subjects were trained on a virtual navigation task before taking a nap. Post-nap tests showed that subjects who dreamed about the task performed better than subjects who did not dream (note that only 4 out of 50 subjects dreamed about the task in this study; Wamsley et al., 2010 ). Using a different approach, Nielsen and colleagues provided additional arguments supporting a link between dreams and memory ( Nielsen et al., 2004 ; Nielsen and Stenstrom, 2005 ). This team demonstrated that dreams preferably incorporate events that the dreamer lived the day before and events that the dreamer lived 7 days before the dream (U shaped curve). Animal studies have shown that after associative learning, the excitability of hippocampal cells increases (which leads to an increase in neuronal plasticity) and then returns to baseline 7 days after training ( Thompson et al., 1996 ). The similarity between the delay of episodic event incorporation into dreams and the delay of post-training cellular plasticity in the hippocampus led the Canadian team to suggest a link between dreaming and episodic memory consolidation.

In summary, the preceding section describes the current state of the art on dreaming, its phenomenology and cerebral correlates and hypotheses about its functions. Some substantial advances have been made, but much remains to be understood.

Unresolved Issues

The link between oneiric behaviors and dream reports.

A piece of evidence in favor of a strong link between REM sleep and dreaming is the oneiric behavior (the appearance of complex motor behaviors when motor inhibition is suppressed during REM sleep) discovered by Sastre and Jouvet (1979) in cats and reproduced by Sanford et al. (2001) in rats. Researchers interpreted these results as the animal acting out its dream. However, as animals do not talk, the link between oneiric behavior and dream recall cannot be tested experimentally. This limitation seriously hampers our understanding of dreaming. In humans, complex motor behaviors (e.g., talking, grabbing, and manipulating imaginary objects, walking, and running) can also occur during REM sleep in a pathological context. This syndrome is called REM sleep behavior disorder (RBD). It can be caused by substance withdrawal (e.g., alcohol, Nitrazepam) or intoxication (e.g., caffeine, tricyclic antidepressants) or by various diseases (e.g., Parkinson’s and Alzheimer’s diseases, pontine neoplasms). According to physicians experts on this syndrome, some patients report dreams that are consistent with their behaviors in REM sleep ( Mahowald and Schenck, 2000 ). According to the literature, however, such matches seem to be loose and not systematic. Only one study has tested whether observers can link dream content to sleep behaviors in RBD ( Valli et al., 2011 ). In this study, each video recording of motor manifestations was combined with four dream reports, and seven judges had to match the video clip with the correctly reported dream content. The authors found that reported dream content can be linked to motor behaviors at a level better than chance. However, only 39.5% of video-dream pairs were correctly identified. Note, however, that because the authors obtained only movements and not behavioral episodes for many RBD patients, the link between videos and dream reports was unfairly difficult to make.

It is important to note that motor behavior during sleep can happen outside of REM sleep. Sleepwalking and sleep terrors, which occur during NREM sleep, are usually not considered dream enactments. However, we know that dreams can happen during NREM sleep, and many patients report dreamlike mentation after awakening from sleepwalking or sleep terrors (71%, according to Oudiette et al., 2009 ). In addition, Oudiette et al. (2009) reported that the dreamlike mentation can correspond with the sleep behavior in NREM sleep. Consequently, the authors concluded that sleepwalking may represent an acting out of corresponding dreamlike mentation.

Recent research suggests that any kind of motor behavior during sleep can be considered an oneiric behavior. One of the challenges for future research is to test the strength of the link between these oneiric behaviors and dream reports in a controlled and systematic way.

Neurophysiological Correlates of Dreaming

Despite the numerous neuroimaging studies of sleep in humans, the neurophysiological correlates of dreaming remain unclear.

Indeed, dreaming can happen during NREM sleep, and although NREM brain activity differs substantially from REM sleep brain activity ( Maquet et al., 2000 ; Buchsbaum et al., 2001 ), some NREM dreams are phenomenologically indistinguishable from REM dreams ( Hobson, 1988 ; Cavallero et al., 1992 ; Cicogna et al., 1998 ; Wittmann et al., 2004 ). This phenomenon is difficult to understand given what we currently know about the sleeping brain and about dreaming. One explanation may rely on the possibility that brain activity during sleep is not as stable as we think.

Brain activity during REM sleep in humans is considered to be well understood ( Hobson and Pace-Schott, 2002 ; Schwartz and Maquet, 2002 ; Nir and Tononi, 2010 ), but several results question this notion. First, contrary to the common belief that dorsolateral prefrontal cortex activity decreases during REM sleep, several studies have reported increased activity in the dorsolateral prefrontal cortex during REM sleep ( Hong et al., 1995 , 2009 ; Nofzinger et al., 1997 ; Kubota et al., 2011 ). Second, brain activity during REM sleep is heterogeneous. The mean regional cerebral blood flow during 1 min of REM sleep (e.g., as reported in Maquet et al., 1996 ) and the regional cerebral blood flow associated with the rapid eye movements of REM sleep ( Hong et al., 2009 ; Miyauchi et al., 2009 ) highlight different brain regions. Finally, few congruencies have been noted in the results of studies investigating brain activity during REM sleep ( Hong et al., 1995 , 2009 ; Maquet et al., 1996 , 2000 ; Braun et al., 1997 , 1998 ; Nofzinger et al., 1997 ; Peigneux et al., 2001 ; Wehrle et al., 2005 ; Miyauchi et al., 2009 ; Kubota et al., 2011 ), even between studies using the same technique and the same contrasts (e.g., Braun et al., 1998 ; Maquet et al., 2000 ), or between studies investigating the same REM event (e.g., brain activity associated with rapid eyes movements, as in Peigneux et al., 2001 ; Wehrle et al., 2005 ; Hong et al., 2009 ; Miyauchi et al., 2009 ). Furthermore, few brain regions are consistently reported across the majority of the studies. This inconsistency suggests great intra- and intersubject variability in brain activity during REM sleep in humans. A challenge for future research will be to find out whether the variability in brain activity during REM sleep can be explained by the variability in dream content.

Because dream reports can be collected after awakenings from any sleep stage, one may hypothesize that the brain activity that subserves dreaming (if such brain activity is reproducible across dreams) is quite constant throughout the night and can be observed during all sleep stages. Some results have supported this hypothesis and encouraged further attention in this direction. Buchsbaum et al. (2001) , for example, reported that metabolism in the primary visual areas and certain parts of the lateral temporal cortex does not fluctuate much across REM and slow-wave sleep. Similarly, Nielsen’s team found that dream recall (vs. no dream recall) was associated with decreased alpha (8–12 Hz) power in the EEG preceding awakening, regardless of the sleep stage (Stage 2 or REM sleep; Esposito et al., 2004 ). Interestingly, some authors have suggested that decreased power in the alpha band during wakefulness reflects search and retrieval processes in long-term memory (for a review, see Klimesch, 1999 ).

Processes of Selection and Organization of Dream Representations

Nielsen’s team found that episodic events from the 1, 7, and 8 days before a dream were more often incorporated into the dream than were events from 2 or 6 days before the dream ( Nielsen et al., 2004 ; results reproduced by Blagrove et al., 2011 ). This result tells us that internal processes control and shape dream content and thus help us to constrain and shape hypotheses about the function and biological basis of dreaming.

At the end of the nineteenth century, Saint-Denys (1867) showed that a sensory stimulus (e.g., the scent of lavender) presented to a sleeping subject without his or her knowledge could induce the incorporation of an event associated with the stimulus (e.g., holidays spent near a lavender field) into the dream, regardless of the delay between the dream and the association stimulus/events (lavender scent/holidays). The author demonstrated that the external world can influence dream content in a direct or indirect way.

Finally, it appears that both external and internal parameters can shape or govern dream content. Nonetheless, few of these parameters are known, and some regularities in the phenomenology of dreams suggest that more influencing parameters remain to be discovered. For example, some individuals experience recurring themes, characters, or places in their dreams. In line with this observation, Michael Schredl’s team showed that the content and style of a person’s life strongly influence dream content ( Schredl and Hofmann, 2003 ). However, the rule(s) governing which lived events are incorporated into dreams remain unknown. Do the representations constituting the dream emerge randomly from the brain, or do they surface according to certain parameters? Similarly, is the organization of the dream’s representations chaotic, or is it determined by rules? Does dreaming have a meaning? What is/are the function(s) of dreaming?

Dreaming, Psychoanalysis, and Neuropsychoanalysis

Psychoanalysis, which was developed by the neurologist Sigmund Freud in the beginning of the twentieth century, proposes answers to the questions raised above. Indeed, his theory of the human mind comprises hypotheses about the rules of selection and organization of the representations that constitute dreams.

At the beginning of the twentieth century, Freud presented the concept of the unconscious. He proposed that a part of our mind is made up of thoughts, desires, emotions, and knowledge that we are not aware of, but that nevertheless profoundly influence and guide our behaviors. In his books (e.g., Freud, 1900, 1920 ), Freud proposes that the unconscious mind comes out in slips and dreams. Its expression, however, is coded within dreams (the work of dream), and unconscious thoughts are distorted before they emerge in the conscious mind of the sleeping subject (manifest content of the dream). As a consequence, the dreamer is not disturbed by repressed and unacceptable thoughts (latent content of the dream) and can continue sleeping (this is the reason why Freud considered dreams the guardians of sleep). Hence, according to Freud, decoding dreams’ latent content provides an access to the unconscious mind.

In Freud’s theory of the mind, unconscious thoughts and feelings may cause the patient to experience life difficulties and/or maladjustment, and free unconscious thoughts can help the patient gain insight into his/her situation. As a consequence, Freud developed techniques to decode dreams and provide a way for an analyst to look inside the words and unconscious images of the patient, and to free them through patient insight. One of these techniques is called free association, and is regarded as an essential part of the psychoanalytic therapy process. In order for an analyst to get to the latent content of a dream, he requires the patient to discuss the dream’s manifest content and encourage free association about the dream. Free association is the principle that the patient is to say anything and everything that comes to mind. This includes decensoring his/her own speech so that he/she truly expresses everything. Over time, the therapist or analyst will draw associations between the many trains of uncensored speech the patient shares during each session. This can lead to patient insight into their unconscious thoughts or repressed memories, and the accomplishment of their ultimate goal of “freedom from the oppression of the unconscious” ( Trull, 2005 ).

Hence, Freud considered that dreams, as well as slips, have a meaning and can be interpreted, so that one is justified in inferring from them the presence of restrained or repressed intentions (Freud, 1900, 1920 ). Note that, in Freud’s theory of the mind, the words “meaning” and “intention” are closely linked: “Let us agree once more on what we understand by the ‘meaning’ of a psychic process. A psychic process is nothing more than the purpose which it serves and the position which it holds in a psychic sequence. We can also substitute the word ‘purpose’ or ‘intention’ for ‘meaning’ in most of our investigations” ( Freud, 1920 ).

In other words, according to Freud, decoding dreams with the free association method provides an access to what makes each of us so special, uncorvering the forces that guide one’s behavior. It gives access to an unknown dimension of ourselves that is fundamental in understanding who we are. It provides access to personal meaning.

This hypothesis, attributing significant importance and meaning to dreams, has rarely been considered by neuroscientists who often consider Freud’s work and theory unscientific.

However, this situation may change as the relationship between psychoanalysis and neuroscience evolves. The starting point was the creation of the International Society for Neuropsychoanalysis in 2000. It was founded by neuropsychologist and psychoanalyst Mark Solms with the intention to promote interactions and collaborations between psychoanalysis and neuroscience. The challenge was serious, as illustrated by neuroscientist Alan Hobson’s aggressiveness in the famous dream debate (Alan Hobson vs. Mark Solms) entitled “Should Freud’s dream theory be abandoned?” held in Tucson, Arizona, in 2006 during the Towards a Science of Consciousness meeting (scientific arguments can be found in Solms, 2000 and Hobson et al., 2000 ). Alan Hobson tried to convince the assembly that Freud was 100% wrong and that Freud’s dream theory was misguided and misleading and should be abandoned. He aimed to demonstrate that Freud’s dream theory is incompatible with what we know about how the brain works. He added that Freud’s dream theory was not scientific because it was not testable or falsifiable. Finally, he presented his model of dreaming, the activation-synthesis hypothesis ( Hobson and McCarley, 1977 ; Hobson et al., 2000 ): “The Activation-Synthesis model of dream construction proposed that the phasic signals arising in the pontine brainstem during REM sleep and impinging upon the cortex and limbic forebrain led directly to the visual and motor hallucinations, emotion, and distinctively bizarre cognition that characterize dream mentation. In doing so, these chaotically generated signals arising from the brain stem acted as a physiological Rorschach test, initiating a process of image and narrative synthesis involving associative and language regions of the brain and resulting in the construction of the dream scenarios.” In contrast, Mark Solms demonstrated that what is currently known about the dreaming brain is at least broadly consistent with Freud’s dream theory. He argued that it is generally accepted that brain stem activation is necessary, but not sufficient, to explain the particular characteristics of dream consciousness. What does explain the particular characteristics of dream consciousness, according to Solms, are the following features of brain activity during REM sleep ( Braun et al., 1997 ): the activation of core forebrain emotion and instinctual drive mechanisms, i.e., the limbic and paralimbic brain areas (the anterior cingulate, insula, hippocampus, parahippocampal gyrus, and temporal pole), and of the posterior perceptual system (the fusiform gyrus, superior, inferior and middle temporal gyrus, and angular gyrus) and the deactivation of executive dorsolateral frontal control mechanisms (the dorsolateral prefrontal cortex). He further argued that his lesion studies ( Solms, 1997 ) are congruent with neuroimaging results because they showed that a total cessation of dreaming results from lesions in the medial part of the frontal lobe and in the temporoparietal junction (whereas no cessation of dreaming was observed for core brainstem lesions or for dorsolateral prefrontal lesions). Finally he emphasized that the activation of motivational mechanisms (such as drives and basic emotions) and of posterior perceptual system associated with deactivation of the executive control (i.e., reality oriented regulatory mechanism) during REM sleep, is broadly consistent with Freud’s dream theory which claims that our instinctual drive states (notably appetitive and libidinal drive system) are relatively disinhibited during sleep. Note that experimental results demonstrating the existence of unconscious representations that guide behavior (e.g., Shevrin and Fritzler, 1968 ; Bunce et al., 1999 ; Arminjon, 2011 , for a review) could also have been cited in support of Freud’s dream theory. This debate was a success for Mark Solms and neuropsychoanalysis. Indeed, at the end of the debate, approximately 100 people voted “no” (i.e., “Freud’s dream theory should not be abandoned”), approximately 50 people voted “yes” and 50 voted “I don’t know”.

Solms’ (1997 , 2000 ) approach to dreaming and his experimental results fundamentally challenged our current understanding of dreaming. He proposes that dreaming and REM sleep are controlled by different brain mechanisms. According to Solms, REM sleep is controlled by cholinergic brain stem mechanisms, whereas dreaming is mediated by forebrain mechanisms that are probably dopaminergic. This implies that dreaming can be activated by a variety of NREM triggers. Several experimental results support this hypothesis.

First, behavioral studies have demonstrated that the link between REM sleep and dream reports is lax. Subjects awakened during NREM sleep can recall dreams at a high rate ( Foulkes, 1962 : 74% of awakenings in NREM sleep were followed by dream reports; Cavallero et al., 1992 : 64%; Wittmann et al., 2004 : 60%); dreams can be recalled after a nap consisting only of NREM sleep ( Salzarulo, 1971 ; Palagini et al., 2004 ); and some individuals never recall dreams, even when awakened from REM sleep ( Pagel, 2003 ). In addition, in healthy subjects with a normal dream recall frequency (around 1 dream recall per week, Schredl, 2008 ), dream recall after an awakening during REM sleep is not systematic: 5–30% of awakenings in REM sleep are not followed by a dream recall, according to the literature (e.g., Dement and Kleitman, 1957a , b ; Foulkes, 1962 ; Hobson, 1988 ). Finally, 5–10% of NREM dreams cannot be distinguished from REM dreams based on their content ( Hobson, 1988 ; Cavallero et al., 1992 ; Cicogna et al., 1998 ; Wittmann et al., 2004 ).

Second, as Solms (2000) argued, the amount of dream recall can be modulated by dopamine agonists ( Scharf et al., 1978 ; Nausieda et al., 1982 ) without concomitant modification of the duration and frequency of REM sleep ( Hartmann et al., 1980 ). Dream recall can be suppressed by focal brain lesions (at the temporo-parieto-occipital junction and ventromedial prefrontal cortex; Solms, 1997 , 2000 ). These lesions do not have any appreciable effects on REM frequency, duration, or density ( Kerr et al., 1978 ; Michel and Sieroff, 1981 ). Finally, some clinical studies suggest that a dream can be triggered by nocturnal seizures in NREM sleep, i.e., by focal brain stimulation. Some cases of recurring nightmares caused by epileptiform activity in the temporal lobe have indeed been reported ( Solms, 2000 ).

Conclusion: Collaboration between Neuroscience and Psychoanalysis Would Benefit Dream Research

Considering the issues that remain unresolved (e.g., neurophysiologic variability, parameter(s) influencing the emergence of representations in dreams, the meaning of dreams), a psychoanalytic perspective would certainly benefit dream research by providing new directions/leads and helping to reach a comprehensive understanding of dreaming.

On the one hand, psychological research has demonstrated that dream content is influenced by one’s personal life, especially personal concerns ( Schwartz, 1999 ; Schwartz and Maquet, 2002 ; Schredl and Hofmann, 2003 ), and some neuroscientists have hypothesized that dreaming is involved in psychological individualism. Thus, both psychology and neuroscience have provided results and hypotheses that validate the possibility that dreaming has something to do with personal and meaningful issues. On the other hand, Freud argued that the unconscious, which guides behaviors and desires, express itself during dreams. The two disciplines’ (cognitive neuroscience and psychoanalysis) convergence on dreaming thus seems obvious; however, very little collaboration has occurred to date.

Note that some experimental studies in psychology have considered the psychoanalytic perspective. For example, Greenberg et al. (1992) attempted “a research-based reconsideration of the psychoanalytical theory of dreaming.” They evaluated the presence of problems (defined as an expression of negative feeling or any situation evoking such feeling or requiring some change or adaptation) during dreaming and pre- and post-sleep wakefulness in two subjects. They showed that problems occurred very frequently in the manifest dream content and that these problems were nearly systematically related to the problems noted during pre-sleep wakefulness. In addition, they observed that effective dreams (i.e., dreams that presented some solution to the individuals’ problems) were followed by a waking state in which the impact of the problems was diminished, whereas ineffective dreams were followed by the persistence of the problems. This study thus confirmed that personal concerns influence dream content. In addition it provided new results suggesting that dreaming may have some psychological problem-solving function (this result recalls the neuroscientific findings that sleep has a cognitive problem-solving function associated with brain reorganization; e.g., Wagner et al., 2004 ; Darsaud et al., 2011 ). Greenberg et al.’s (1992) study managed to quantify personal issues and clearly broadened the cognitive neuroscience perspective on dreaming. To proceed further, approaches integrating psychoanalysis and neuroscience must now be developed. Several subjective issues at the core of the psychoanalytic approach, such as the concept of personal meaning, the concept of unconscious episodic memory and the subject’s history, are not addressed or considered in cognitive neuroscience. This limitation hampers the understanding of psychological and neurophysiological functioning in humans. These issues must be addressed, and the expertise of psychoanalysts in singularity and personal meaning is needed to do so in neuroscience and to further the understanding of dreaming and of the psyche.

Conflict of Interest Statement

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords: dream, neurophysiological correlates of dreaming, dream functions, unconscious, personal meaning, neuroimaging, psychoanalysis

Citation: Ruby PM (2011) Experimental research on dreaming: state of the art and neuropsychoanalytic perspectives. Front. Psychology 2 :286. doi: 10.3389/fpsyg.2011.00286

Received: 16 May 2011; Accepted: 10 October 2011; Published online: 18 November 2011.

Reviewed by:

Copyright: © 2011 Ruby. This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.

*Correspondence: Perrine M. Ruby, INSERM U1028, Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, Lyon F-69000, France. e-mail: perrine.ruby@inserm.fr

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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7 surprising facts about dreams — why we have them and what they mean

Andrea Muraskin

An abstract 3d cloud model in the bedroom. (3d render) Eoneren/Getty Images/E+ hide caption

I had a nightmare last night.

It began like many of my dreams do – I was on vacation with my extended family. This time, we were in Australia, visiting family friends in a big house. Things took a turn when — in some way that I can’t quite explain — I got mixed up in this Australian family’s jewelry theft and smuggling operation. And I lied about it in front of my relatives, to protect myself and my co-conspirators. Before I woke up, I was terrified I’d be sent to prison.

The dream seems bizarre, but when I pick the narrative apart, there are clear connections to my waking life. For instance, I recently listened to a podcast where a pair of fancy hairpins suspiciously go missing during a family gathering. Moreover, I’m moving tomorrow and still have packing to do. When the movers arrive in the morning, if I haven't finished packing, I'll face the consequences of my lack of preparedness – a crime, at least to my subconscious.

This story also appears in the June 2 issue of the NPR Health newsletter. Click here to subscribe.

Dr. Rahul Jandial, neurosurgeon, neuroscientist and author of This is Why You Dream: What Your Sleeping Brain Reveals About Your Waking Life , says the major themes and images of vivid dreams like these are worth paying attention to, and trying to derive meaning from. (For me, I decided that the next time I have to move, I’m taking the day before off!)

Dr. Rahul Jandial Sam Lim/Penguin Random House hide caption

I spoke with Dr. Jandial about what else we can learn from our dreams, including some of modern science’s most remarkable findings, and theories, about the dreaming brain.

1. Dreams are not random

From dream diaries recorded in ancient Egypt and China to reports from anthropologists in the Amazon, to surveys of modern Americans, evidence shows our dreams have a lot in common. For example, being chased and falling are pretty consistent.

“Reports of nightmares and erotic dreams are nearly universal,” Jandial says, while people rarely report dreaming about math. Jandial says the lack of math makes sense because the part of your brain primarily responsible for logic — the prefrontal cortex — is typically not involved in dreaming.

2. Our brains are super active when we dream

Jandial learned something fundamental about dreams in the midst of performing brain surgery.

It was awake surgery – he’d numbed the scalp and partially opened the skull. (The brain does not feel pain). Jandial was operating on the left temporal lobe, where language is typically located. Working carefully to avoid damage, he went millimeter by millimeter, stimulating the neurons, and asking the patient to count to ten at each spot.

But after one such zap of electricity, Jandial’s patient experienced a nightmare that had recurred for him since childhood.

Research has since confirmed that nightmares, and all dreams, arise from brain activity. “Now we know from different measurements of electricity and metabolic usage, the sleeping-dreaming brain is burning hot. It's sparking with electricity. We might be asleep, but the brain is on fire,” Jandial says.

3. When you first wake up, or while you're drifting off, is fertile time for creativity

Salvador Dali had a method for capturing his thoughts just as he was falling asleep, which Jandial recounts in This is Why You Dream . The artist would sit in a chair holding a large key above a plate on the floor. When he nodded off, the key would drop on the plate and wake him up. Then he’d sketch what he remembered from the last few moments of sleep – an inspiration for his surrealist paintings. Brain imaging studies support the potential of sleep-entry as a moment of insight, says Jandial.

Fortunately for those of us who prefer to fall asleep and stay there, thank you very much, you can also get inspiration from your dreams when you first wake up. “I get all my ideas when I wake slowly,” Jandial says. He writes down what he remembers in the first few minutes after waking, before checking the news or Instagram. It’s not all great stuff, “But when there are good ideas, it's from that time. It's not from two o'clock with my espresso,” he says.

4. Nightmares? Write a new script

Jandial says nightmares around occasional stressful events, like my dream about the jewelry heist – are usually not cause for concern. But if you’re stuck in a loop of recurring fearful dreams, there is something you can try: Imagery Rehearsal Therapy.

This is something you can do with a therapist. “If [a patient has] a recurrent nightmare of an explosion or an airplane crashing, they'll go to the therapist to draw out the map of the dream, the dreamscape, if you will, and then they'll rehearse that the airplane landed safely,” or that they arrived home from a drive instead of crashing, Jandial explains. After time, he says many patients see their nightmares change.

5. Dreams about cheating are normal. They don’t mean there's something wrong with your relationship

In surveys, a majority of people report erotic dreams. And for people in relationships, these dreams contain “high rates of infidelity, whether people report being in healthy relationships or unhealthy relationships,” Jandial says.

But sexy dreams have rules too. “When you look at the pattern of erotic dreams, the acts seem to be wild, but the characters are surprisingly narrow. Celebrities, even family members, repellent bosses; it's a small collection of people as a pattern.” Jandial and others theorize that having sexual dreams about people familiar to us may be a feature our brains evolved to keep us open to procreation and increase the likelihood of the species’ survival.

6. Near the end of life, dreams can provide comfort

Treating patients at City of Hope cancer center in Los Angeles, Jandial observes a phenomenon he calls “dreams to the rescue.” For some patients near the end of their lives, “even though the day is filled with struggle, the dreams are of reconciliation, of hope, of positive emotions. I was surprised to find that end-of-life dreams are a common thing, and they lean positive.”

Jandial says there’s evidence that death may come with one final dream. “Once the heart stops, with the last gush of blood up the carotid [artery] to the brain, the brain's electricity explodes in the minute or two after cardiac death…Those patterns look like expansive electrical brainwave patterns of dreaming and memory recall,” Jandial says.

7. Dreams can be ‘a portal to your inner self’ — and mental health

Everyone has anxiety dreams from time to time. Some are literal, like dreaming you’re on a podium naked when you actually have to give a speech the next day, says Jandial. But others can be more symbolic, and these are worth tuning in to.

Jandial remembers one he had during the pandemic. In waking life, he’d just learned to sail. In the dream he was sailing a boat and, “there was a massive waterfall,” he recounts. “And I was sailing horizontally and I had to constantly keep the helm, or the wheel, up-river just to go straight and not fall off.”

He interprets it as his brain’s way of helping him process a difficult time. He was raising teenagers and working as a cancer surgeon amid COVID fears. “There were wars on many fronts for me at that time. And what I walked away with is just by avoiding going all over the waterfall, you're doing it.”

He says if you have a powerful dream, it’s worth thinking about why. “Dreams with a strong emotion and a powerful central image, those are ones not to ignore,” he says. “The dreaming brain is serving a function, and if it gives you a nugget of an emotional and visual dream, reflect on that. That's a portal to yourself that no therapist can even get to.”

And repeated anxiety dreams, he says “I think that's something to pay attention to. That might be a vital sign for your mental health.”

International Association for the Study of Dreams

Journal: Dreaming

Dreaming journal of the association for the study of dreams.

Dreaming is a peer-reviewed multidisciplinary journal devoted specifically to dreaming.

The journal publishes scholarly articles related to dreams from any discipline and viewpoint. This includes biological aspects of dreaming and sleep/dream laboratory research; psychological articles of any kind related to dreaming; clinical work on dreams regardless of theoretical perspective (Freudian, Jungian, existential, eclectic, etc.); anthropological, sociological, and philosophical articles related to dreaming; and articles about dreaming from any of the arts and humanities.

The journal Dreaming has a 2011 impact factor of 0.841, ranking it 68th out of 125 journals in the category “Psychology, Multidisciplinary”

• Editorial Staff  / Contact the Editor
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• Pricing for individual articles in Dreaming journal [APA PsychArticlest]
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• Online Articles

DREAMING – IASD’S SCHOLARLY AND MULTIDISCIPLINARY JOURNAL

Because of its large and diverse membership IASD is now able to cover the full range of activities and output that would be expected of an organization “dedicated to the pure and applied investigation of dreams and dreaming.” Part of that range of activities and output is IASD’s scholarly journal, Dreaming . Below are answers to some common questions about the journal.

Why is the journal important to IASD?

The journal ensures that IASD, while covering applied and personal aspects of working with dreams, also covers the publishing of original scholarly works (which can of course be about applied and personal work, as well as being from various academic disciplines). This publishing adds prestige to the work that IASD undertakes in Continuing Education, public education, and the holding of conferences. The journal also acts as outreach to various scholarly and therapeutic communities world-wide, showing them that such work on dreams can be done, and enables IASD to appear in many places as the broadcaster of the work. Dream Time also publishes original scholarly works, usually shorter articles, and these similarly get IASD cited world-wide as the organization stimulating and broadcasting the work.

Why is the journal important to scholarly work on dreams?

There are many journals that compete with Dreaming to publish research articles on dreaming. However, those journals are usually within one specific field, such as the study of personality, or ethnology, and so our journal enables authors, where they could probably have got the article into a single discipline type of journal if they wanted to, to instead publish alongside articles from other disciplines, but all of which have dreams as their subject. This can lead to future multidisciplinary work, as researchers get to read articles about dreams from disciplines they may be unfamiliar with. It also enables individuals whose interest is mainly dreams to receive a broad range of articles just on dreams.

What happens to manuscripts that are submitted to the journal?

Manuscripts are read by 3-6 reviewers, from within and outside the discipline of the author. The reviewers are not told the name(s) of the author(s), although they can sometimes guess it, and the authors are not told who has reviewed it. Each reviewer writes a report on the article, assessing its strengths and weaknesses, and making constructive comments and suggestions. This stage should take 3-4 months, with each reviewer making a recommendation about the manuscript:

1) that it be accepted as it is – this is very rare, even the best researchers make mistakes about what should or should not be in the article, or are unclear about what they mean; 2) that it be accepted subject to modification – this is a common recommendation where the value of the work is obvious, but where some deficiencies in the manuscript need to be addressed; maybe there has been insufficient acknowledgement of previous work, or previous work is acknowledged that is in fact irrelevant; 3) that the author(s) be invited to resubmit the work with major changes – this is where the value of the work is unclear, but the authors are given another chance to make their case, or, in the case of experimental work, even to undertake further experiments; 4) rejection .

The Editor then makes a decision based on what the reviewers have written and recommended, and this is communicated to the author. If the final decision is 2) above, then authors will often take up to 2 months to rewrite, if 3), then it can take up to 6 months.

If you want to have your name on the list of available reviewers, then please inform the Editor-in-Chief, with mention of your areas of interest .

What other checks are there on the quality of the journal?

Each year the world’s top 6000 journals, from science, social science, and the arts and humanities, are assessed by Journal Citation Reports for how frequently their articles are referred to: In other words, we can ask the questions, Have articles in Dreaming provoked further research? Are articles in Dreaming worth referring to? Journal Citation Reports measures how often articles in each journal are cited, that is, how many people reading a journal cite it in work they are writing. Dreaming does well on this, being quoted above the average. Just looking at some of the journals that start with A, Dreaming is being cited more than the journals Adolescence, Applied Nursing Research, Aids Patient Care Studies, Africa, American Criminal Law Review, Adult Education Quarterly, Anthropology Quarterly, Ageing Society, Australian Journal of Psychology, American Political Quarterly, American Journal of Psychotherapy, and American Journal of Art Therapy. These are just a few of the journals starting with A that Dreaming exceeds in level of world citation. It also exceeds GLQ-Journal of Lesbian and Gay Studies, American Journal of Psychology, and Canadian Psychologist, and we are just behind Creativity Research Journal. Hopefully with its 3 publication outlets ( Dreaming , Dream Time , and the website) IASD will be not just the publisher of the majority of the world’s original works on dreaming, but Dreaming (and hence IASD) could be the most cited source of new scholarly work on dreaming, and a model of a multidisciplinary journal that others may copy.

The journal DREAMING has a 2011 impact factor of 0.841, ranking it 68th out of 125 journals in the category “Psychology, Multidisciplinary”

Why are the articles so detailed?

Even if an article is of interest you may not need or want to read every word of it, some people may be more interested in the conclusions, others in how the work was done, others just want a brief summary of the whole thing. The article has to satisfy a wide range of readers and researchers, some of whom may be reading the article 20 years from now. Take the example of the discovery of REM sleep, we all know something about this subject, much of it is in public knowledge, in TV documentaries, or in summary articles and popular works. But as well as having the summaries and the speculations and the popular works and the subsequent research based on the discovery, there has to be an archived full account, available for future generations, of the discovery of REM sleep. This enables others to copy and repeat what was done, in order to check that the research and results are true. For example, in the original paper in 1953 reporting that dreams occur during REM sleep, there is detail about how the researchers defined dreams. This led to subsequent work that found that with a laxer criterion for calling a report a dream then dreams could also be found in non-REM sleep. The important point is that somewhere the full details of work done has to be recorded. IASD has decided that it will, in addition to all its other activities, publish a journal as such a detailed archive.

Detailed, but readable at one sitting?!

There have been many articles in Dreaming that are not only detailed, but are readable at one sitting too! The following is a personal, partial, and necessarily brief selection. “Nightmare Frequency and Related Sleep Disturbance as Indicators of a History of Sexual Abuse”; “Effect of Encouragement on Dream Recall”; “Perestroika of the Self: Dreaming in the U.S.S.R.”; “How Might We Explain the Parallels Between Freud’s 1895 Irma Dream and his 1923 Cancer?”; “Making Connections in a Safe Place: Is Dreaming Psychotherapy?”; all of Carla Hill’s papers on the effects of associating to dreams; “Dreams Following Hurricane Andrew”; “Anxiety Dreams in School-Aged Children”; “A Dream Is a Poem, A Metaphorical Analysis”; “The Dream as a Tool for Historical Research: Reexamining Life in Eighteenth Century Virginia Through the Dreams of a Gentleman: William Byrd, II, 1674-1744”; “Preconscious Mental Activity and Scientific Problem-Solving: A Critique of The Kekulé Dream Controversy”; “Just How Lucid are Lucid Dreams?”; “Dreaming in a Totalitarian Society; A Reading of Charlotte Beradt’s The Third Reich of Dreams”, “The Presentation of Dreaming and Dreams in Introductory Psychology Textbooks: A Critical Examination with Suggestions for Textbook Authors and Course Instructors”; “Freud’s Dream of the Botanical Monograph and Cocaine the Wonder Drug”; “Touring the Dream Factory: The Dream-Film Connection in The Wizard of Oz and A Nightmare on Elm Street”

Dreaming is multidisciplinary

The issues of Dreaming will obviously be appreciated by more readers if they each have a wide disciplinary range, and the aim has been to achieve that in each issue (except where it’s a special issue), assuming that articles of sufficient quality are available at the time. In order to keep up interest of the wider IASD membership in the journal, we have started summarizing individual Dreaming articles in Dream Time , with the possibility of including in Dream Time explanatory material that may not be, or cannot be, in the original articles.

New developments

All of the past abstracts of articles from Dreaming are on the IASD website here at www.asdreams.org. IASD volunteers are also in process of making one complete article per issue of Dreaming available to the public on the online Dreaming articles page. There are also invited website articles that provide commentaries on particular journal articles, and there is a discussion bulletin board for detailed discussion by anyone of individual articles.

If you have any questions or comments about the journal, please send them to the Editor-in-Chief, Deirdre Barrett, PhD.

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Dreams: Why They Happen & What They Mean

Staff Writer

Eric Suni has over a decade of experience as a science writer and was previously an information specialist for the National Cancer Institute.

Want to read more about all our experts in the field?

Alex Dimitriu

Psychiatrist

Dr. Dimitriu is the founder of Menlo Park Psychiatry and Sleep Medicine. He is board-certified in psychiatry as well as sleep medicine.

Sleep Foundation

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Table of Contents

What Are Dreams?

Why do we dream, when do we dream, do dreams have meaning, what are types of dreams, what are nightmares, do dreams affect sleep, how can you remember dreams, how can you stop nightmares.

• Dreams are mental, emotional, or sensory experiences that take place during sleep.
• Dreams are the most common and intense during REM sleep when brain activity increases, but no one knows for sure why we dream.
• Dreaming is normal and healthy, but frequent nightmares can interfere with sleep.
• Waking up gradually and journaling your dreams may help you remember them better.

Dreams are one of the most fascinating and mystifying aspects of sleep. Since Sigmund Freud helped draw attention to the potential importance of dreams in the late 19th century, considerable research has worked to unravel both the neuroscience and psychology of dreams.

Despite this advancing scientific knowledge, there is much that remains unknown about both sleep and dreams. Even the most fundamental question — why do we dream at all? — is still subject to significant debate.

While everyone dreams, the content of those dreams and their effect on sleep can vary dramatically from person to person. Even though there’s no simple explanation for the meaning and purpose of dreams, it’s helpful to understand the basics of dreams, the potential impact of nightmares, and steps that you can take to sleep better with sweet dreams.

Is Your Troubled Sleep a Health Risk?

A variety of issues can cause problems sleeping. Answer three questions to understand if it’s a concern you should worry about.

Dreams are images, thoughts, or feelings that occur during sleep. Visual imagery is the most common Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , but dreams can involve all of the senses. Some people dream in color while others dream in black and white , and people who are blind tend to have more dream components related to sound, taste, and smell Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source .

Studies have revealed diverse types of dream content, but some typical characteristics of dreaming include:

• It has a first-person perspective.
• It is involuntary.
• The content may be illogical or even incoherent.
• The content includes other people who interact with the dreamer and one another.
• It provokes strong emotions.
• Elements of waking life are incorporated into content.

Although these features are not universal, they are found at least to some extent in most normal dreams.

Debate continues among sleep experts Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source about why we dream. Different theories Trusted Source Division of Sleep Medicine at Harvard Medical School A production of WGBH Educational Foundation and the Harvard Medical School Division of Sleep Medicine. View Source about the purpose of dreaming Trusted Source National Center for Biotechnology Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source include:

• Building memory: Dreaming has been associated with consolidation of memory, which suggests that dreaming may serve an important cognitive function of strengthening memory and informational recall.
• Processing emotion: The ability to engage with and rehearse feelings in different imagined contexts may be part of the brain’s method for managing emotions.
• Mental housekeeping: Periods of dreaming could be the brain’s way of “straightening up,” clearing away partial, erroneous, or unnecessary information.
• Instant replay: Dream content may be a form of distorted instant replay in which recent events are reviewed and analyzed.
• Incidental brain activity: This view holds that dreaming is just a by-product of sleep that has no essential purpose or meaning.

Experts in the fields of neuroscience and psychology continue to conduct experiments to discover what is happening in the brain during sleep, but even with ongoing research, it may be impossible to conclusively prove any theory for why we dream.

On average, most people dream for around two hours per night. Dreaming can happen Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source during any stage of sleep , but dreams are the most prolific and intense during the rapid eye movement (REM) stage.

During the REM sleep stage, brain activity ramps up considerably compared to the non-REM stages, which helps explain the distinct types of dreaming Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source during these stages. Dreams during REM sleep are typically more vivid, fantastical, and/or bizarre even though they may involve elements of waking life. By contrast, non-REM dreams tend to involve more coherent content that involves thoughts or memories grounded to a specific time and place.

REM sleep is not distributed evenly through the night. The majority of REM sleep happens during the second half of a normal sleep period, which means that dreaming tends to be concentrated in the hours before waking up.

How to interpret dreams, and whether they have meaning at all, are matters of considerable controversy. While some psychologists have argued that dreams provide insight into a person’s psyche or everyday life, others find their content to be too inconsistent or bewildering to reliably deliver meaning.

Virtually all experts acknowledge that dreams can involve content that ties back to waking experiences although the content may be changed or misrepresented. For example, in describing dreams, people often reference people who they recognize clearly even if their appearance is distorted in the dream Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source .

The meaning of real-life details appearing in dreams, though, is far from settled. The “continuity hypothesis” in dream research holds that dreams and waking life are intertwined with one another and thus involve overlapping themes and content. The “discontinuity hypothesis,” on the other hand, sees thinking during dreams and wakefulness as structurally distinct.

While analysis of dreams may be a component of personal or psychological self-reflection, it’s hard to state, based on the existing evidence, that there is a definitive method for interpreting and understanding the meaning of dreams in waking, everyday life.

Dreams can take on many different forms. Lucid dreams occur when a person is in a dream while being actively aware that they are dreaming. Vivid dreams involve especially realistic or clear dream content. Bad dreams are composed of bothersome or distressing content. Recurring dreams involve the same imagery repeating in multiple dreams over time.

Even within normal dreams, there are certain types of content that are especially identifiable. Among the most recognizable and common themes Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source in dreams are things like flying, falling, being chased, or being unable to find a bathroom.

In sleep medicine, a nightmare is a bad dream that causes a person to wake up from sleep Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . This definition is distinct from common usage that may refer to any threatening, scary, or bothersome dream as a nightmare. While bad dreams are normal and usually benign, frequent nightmares may interfere with a person’s sleep and cause impaired thinking and mood Trusted Source American Academy of Sleep Medicine (AASM)|National Library of Medicine, Biotech Information View Source during the daytime.

In most cases, dreams don’t affect sleep. Dreaming is part of healthy sleep and is generally considered to be completely normal and without any negative effects on sleep.

Nightmares are the exception. Because nightmares involve awakenings, they can become problematic if they occur frequently. Distressing dreams may cause a person to avoid sleep, leading to insufficient sleep. When they do sleep, the prior sleep deprivation can induce a REM sleep rebound that actually worsens nightmares. This negative cycle can cause some people with frequent nightmares to experience insomnia as a chronic sleep problem.

For this reason, people who have nightmares more than once a week, have fragmented sleep, or have daytime sleepiness or changes to their thinking or mood should talk with a doctor Trusted Source Medline Plus MedlinePlus is an online health information resource for patients and their families and friends. View Source . A doctor can review these symptoms to identify the potential causes and treatments of their sleeping problem.

For people who want to document or interpret dreams, remembering them is a key first step. The ability to recall dreams can be different for every person and may vary based on age Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . While there’s no guaranteed way to improve dream recall, experts recommend certain tips Trusted Source American Psychological Association (APA) APA is the leading scientific and professional organization representing psychology in the United States, with more than 121,000 researchers, educators, clinicians, consultants and students as its members. View Source :

• Think about your dreams as soon as you wake up. Dreams can be forgotten in the blink of an eye, so you want to make remembering them the first thing you do when you wake up. Before sitting up or even saying good morning to your bed partner, close your eyes and try to replay your dreams in your mind.
• Have a journal or app on-hand to keep track of your dream content. It’s important to have a method to quickly record dream details before you can forget them, including if you wake up from a dream in the night. For most people, a pen and paper on their nightstand works well, but there are also smartphone apps that help you create an organized and searchable dream journal.
• Try to wake up peacefully in the morning. An abrupt awakening, such as from an alarm clock, may cause you to quickly snap awake and out of a dream, making it harder to remember the dream’s details.
• Remind yourself that dream recall is a priority. In the lead-up to bedtime, tell yourself that you will remember your dreams, and repeat this mantra before going to sleep. While this alone can’t ensure that you will recall your dreams, it can encourage you to remember to take the time to reflect on dreams before starting your day.

People with frequent nightmares that disturb sleep should talk with a doctor who can determine if they have nightmare disorder or any other condition affecting their sleep quality. Treatment for nightmare disorder often includes talk therapy that attempts to counteract negative thinking, stress, and anxiety that can worsen nightmares.

Many types of talk therapy attempt to reduce worries or fears, including those that can arise in nightmares. This type of exposure or desensitization therapy helps many patients reframe their emotional reaction to negative imagery since trying to simply suppress negative thoughts may exacerbate nightmares Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source .

Another step in trying to reduce nightmares is to improve sleep hygiene , which includes both sleep-related habits and the bedroom environment . Healthy sleep hygiene can make your nightly sleep more predictable and may help you sleep soundly through the night even if you have bad dreams. Examples of healthy sleep tips include:

• Follow a stable sleep schedule: Keep a steady schedule every day, including on weekends or other days when you don’t have to wake up at a certain time.
• Choose pre-bed content carefully: Avoid scary, distressing, or stimulating content in the hours before bed since it may provoke negative thoughts during sleep.
• Wind down each night: Exercising during the day Trusted Source Centers for Disease Control and Prevention (CDC) As the nation’s health protection agency, CDC saves lives and protects people from health threats. View Source can help you sleep better at night. In the evening, try to allow your mind and body to calmly relax before bed such as with light stretching, deep breathing, or other relaxation techniques.
• Limit alcohol and caffeine: Drinking alcohol can cause more concentrated REM sleep later in the night, heightening the risk of nightmares. Caffeine is a stimulant that can throw off your sleep schedule and keep your brain wired when you want to doze off.
• Block out bedroom distractions: Try to foster a sleeping environment that is dark, quiet, smells nice, and has a comfortable temperature. A supportive mattress and pillow can make your bed more inviting and cozy. All of these factors make it easier to feel calm and to prevent unwanted awakenings that can trigger irregular sleep patterns.
• Study Finds Bedtime Procrastination Impacts Sleep Quality
• Only Murders While You’re Sleeping: The Parasomnia Defense
• Crime Risk and Depression Differentially Relate to Aspects of Sleep
• Mechanism During Sleep Found to Determine Which Memories Last

About Our Editorial Team

Eric Suni, Staff Writer

Medically Reviewed by

Alex Dimitriu, Psychiatrist MD

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Scarpelli, S., Bartolacci, C., D’Atri, A., Gorgoni, M., & De Gennaro, L. (2019). Mental sleep activity and disturbing dreams in the lifespan. International Journal of Environmental Research and Public Health, 16(19), 3658.

Division of Sleep Medicine at Harvard Medical School. (2021, October 1). Science of Sleep: What is Sleep?.

Purves, D., Augustine, G. J., & Fitzpatrick, D. et al. (Eds.). (2001). The Possible Functions of REM Sleep and Dreaming. In Neuroscience (2nd Edition).

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Payne, J. D., & Nadel, L. (2004). Sleep, dreams, and memory consolidation: the role of the stress hormone cortisol. Learning & memory (Cold Spring Harbor, N.Y.), 11(6), 671–678.

Kahn, D., Stickgold, R., Pace-Schott, E. F., & Hobson, J. A. (2000). Dreaming and waking consciousness: A character recognition study. Journal of Sleep Research, 9(4), 317–325.

Schredl, M., Ciric, P., Götz, S., & Wittmann, L. (2004). Typical dreams: stability and gender differences. The Journal of psychology, 138(6), 485–494.

Paul, F., Schredl, M., & Alpers, G. W. (2015). Nightmares affect the experience of sleep quality but not sleep architecture: an ambulatory polysomnographic study. Borderline personality disorder and emotion dysregulation, 2, 3.

Aurora, R. N., Zak, R. S., Auerbach, S. H., Casey, K. R., Chowdhuri, S., Karippot, A., Maganti, R. K., Ramar, K., Kristo, D. A., Bista, S. R., Lamm, C. I., Morgenthaler, T. I., Standards of Practice Committee, & American Academy of Sleep Medicine (2010). Best practice guide for the treatment of nightmare disorder in adults. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine, 6(4), 389–401.

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Mangiaruga, A., Scarpelli, S., Bartolacci, C., & De Gennaro, L. (2018). Spotlight on dream recall: the ages of dreams. Nature and science of sleep, 10, 1–12.

Barrett, D., & Luna, K. (2018, December). Speaking of psychology: The science of dreaming. American Psychological Association.

Kröner-Borowik, T., Gosch, S., Hansen, K., Borowik, B., Schredl, M., & Steil, R. (2013). The effects of suppressing intrusive thoughts on dream content, dream distress and psychological parameters. Journal of sleep research, 22(5), 600–604.

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How australian documentarians matthew salleh and rose tucker found slices of the american dream in former pizza huts.

The latest film by the 'Barbecue' and 'We Don’t Deserve Dogs' duo premieres at SXSW Sydney in October 2024.

In the late 60s, a decade after first slinging slices in America's midwest, Pizza Hut started taking the second part of its name seriously. Thanks to a design by architect Richard D Burke, who agreed to a $100 fee for each location that opened — a hugely lucrative deal, it turned out — everyone knows the fast-food chain's famous silhouette. From 70s, 80s and 90s childhoods in particular, that angular roof instantly brings to mind family feasts, birthday parties and all-you-can-eat pizza specials that gave Sizzler a run for its money in Australia, dessert bar included.

Brooklyn-based Aussie filmmakers Matthew Salleh and Rose Tucker, who previously made Barbecue and We Don't Deserve Dogs , are well-are of this history. In fact, they've made a documentary that's partly about it: Slice of Life: The American Dream. In Former Pizza Huts . They're equally cognisant of the nostalgic feeling that old Pizza Huts bring. "I kept thinking back to the soft-serve machine. As a kid, I was just drawn to that machine. I just wanted the soft serve with the sprinkles, the coloured sprinkles on top — my Pizza Hut dream was the soft-serve machine," Tucker tells Concrete Playground , chatting about the film that'll premiere at 2024's SXSW Sydney  in October.

Audiences will indeed remember their own experiences in Pizza Hut's distinctive buildings while watching Slice of Life . Craving pizza comes with the territory, too. Salleh and Tucker haven't tucked into Pizza Hut while making the movie, purely "because they're not in New York", Salleh advises, but they still understand the urge. "Occasionally we're editing and we'll see shots of pizzas, and I'll be like 'we need pizza'. Luckily, living in Brooklyn, you only have to walk about 150 metres to find some pretty awesome pizza. So if anything, it's just made me eat a lot more pizza in New York," he continues.

Recalling times gone by for a global chain is just one of this doco's ingredients, however. Consider it a topping; at its heart, this film's main focus is right there in its title. While they weave in the Pizza Hut origin story, and that of those huts known around the planet, Salleh and Tucker are interested in how such immediately recognisable structures have lived on in new guises in the US once the brand left plenty of those buildings. Be it a Texan karaoke bar, a LGBTQIA+ church in Florida or a cannabis dispensary in Colorado, what made-over former Pizza Huts say about the pursuit of the American dream today is also as pivotal to their documentary as dough is to the world's most-beloved Italian dish.

The pair boast a tried-and-tested approach, as their first two feature-length films also capitalised upon. Take one thing — barbecue cooking, canines, ex-Pizza Huts — then dive deep, building a portrait of what humanity's interaction with said subject explains about the world, people in general and/or a specific country. All three titles have also enjoyed a relationship with SXSW. Barbecue premiered at SXSW Austin in 2017, and was picked up by Netflix as a result. Then, We Don't Deserve Dogs was selected for the pandemic-affected US event in 2020 . Now, after being one of the first films announced for this year's lineup , Slice of Life will bow at SXSW Sydney 's second year .

  View this post on Instagram   A post shared by Urtext Films (@urtext)

If there's a spark of familiarity to Salleh and Tucker's latest concept, that's because the Used to Be a Pizza Hut blog has also been operating in this territory. It was a helpful resource for them, with its founder Mike Neilson among their interviewees. Wondering if the duo ever thought of expanding their remit beyond US Pizza Huts, as the site covers? They've dubbed their American focus "geographical discipline". Explains Salleh: "this is our documentary version of the great American road movie, I guess. We were tempted to to make this thing global, but then we knew we'd be probably making it for the next 20 years." Adds Tucker: "we really could, they built these things all over the place."

What does having SXSW's support mean to the pair? "It's amazing. As an independent filmmaker, it's really, really tough to even get into a festival, so to do it with SXSW now three times is pretty special," says Tucker. "We're basically independent DIY, and so to be able to go to a festival that also has a little bit of a market and business side to it as well, and tries to bring those elements together is, I guess, what we try to do on a daily basis — bringing together the business of what we do and the creativity of what we do. So it's been a good fit over the years," advises Salleh.

When you hone in on a specific topic per documentary, where does inspiration come from? Also, how do you know that you're onto a winner of an idea, and then get your subjects onboard? From the way that they handle to on-the-road projects to finding their former Pizza Huts and what they learned about America while making Slice of Life , we chatted through the details with Salleh and Tucker.  

On Where Salleh and Tucker Find Inspiration

Rose: "I guess you could say we're just chronic people-watchers, and we're just interested in things that people get passionate about. So with Barbecue , that one's a fairly obvious one: people get really fired up about cooking and gathering with their family. There's a little bit of patriotism involved in that as well — everyone thinks they have the best barbecue — so it's a thing that gets people talking and gets people passionate.

And similarly with dogs. People love their dogs and that's a global phenomenon."

Matthew: "We have a scribble board of hundreds of ideas, and it's a survival of the fittest. It's when we can see that an idea will play out in a in a whole film, rather than be a short or something like that.  

I often say there's a taxi or Uber driver test, where an Uber driver will ask what you do for a living and you explain the film you're making, and they go 'ohh you have to go interview my best friend' — or if they know someone or if they can tell their passionate story.

It was a similar thing with this new film, we would talk about it with people and they go 'ohh back in my town, the old Pizza Hut used to be ...'. There was either nostalgic remembrance of what it used to be or 'ohh now it's a mattress store', 'now it's a Hertz car rental' or any sort of interesting thing.

So it seems to have really gotten people interested in talking passionately. And it's interesting as well, because there's a lot going around at the moment with people re-examining pop culture nostalgia and stuff like that.

But then it just presented this amazing opportunity for us where we were actually able to go 'well, here's something pop culture and nostalgic, but it still exists in this strange way now'. So it was a way that we could combine the nostalgic memories of old Pizza Huts with this entrepreneurial spirit of people starting up businesses potentially in buildings they never thought they would, but making it work somehow."

Rose: "There's this idea of community that flows through these buildings. So when they're a Pizza Hut, they're a community hub. And it would be a really big deal if your small town got a Pizza Hut. It was a big, big deal. Then when they close down, that hub goes away.

But now they're sprouting up again in these second, third, fourth, fifth lives, and those places are now similarly hubs for the community. They're the places that we were really focusing on trying to find — those places that still are that gathering point, or that third place that that people are drawn to and want to spend time with people in."

Matthew: "And in a world where those sort of places are dying away, making this film coming out of the pandemic, where we had to eliminate that third place, those gathering places in the community‚ and even the fact that a lot of these businesses survived through some of those tougher times so that they can flourish now — that was very much part of our mind when we were making this. It's places where people can just get together, whether it's a church or whether it's a restaurant …"

Rose: "Or a karaoke bar."

Matthew: "… and just be part of their community."

On Finding Slice of Life 's Old Pizza Huts in Small Towns Across America Where Having the Chain in Town Was Originally a Source of Pride

  Rose: "We were actively seeking small towns. The most-rural town we visited is Walsenburg, Colorado — and that is in the middle of the country, small town, and it was a big deal.

From memory, I think that the only other fast food they currently have is a Subway."

Matthew: "Much less romantic."

Rose: "But it was a huge deal to get this big building, this big Pizza Hut, that was right on the edge of town — it was a massive deal. And it was where all the sports teams would go on the weekend after finishing their game, it's where kids would go after their prom for their after party. Like, this was the place."

Matthew: "And I think it was this idea that the town over didn't get the Pizza Hut — we got the Pizza Hut.  

We're all very hip and cosmopolitan now, we might almost chuckle a little at a chain store having meaning, something important to a community — but back in the 60s, 70s and 80s, when towns, especially towns across America, were trying to grow and trying to be something, these were the test of having made it, as it were. So that seemed to be a big part of it.

And then there's also a practical consideration, because we basically had to become world experts in these old Pizza Hut buildings — and they survive more in small towns, because I think the ones that were in big cities have just gotten levelled with the passage of time."

Rose: "Or they were never built in the first place. This is a building that worked in suburbia and out on the highways.  I don't think there were any traditional Pizza Hut buildings built within New York City, where we live at the moment. So you're not going to find one here. But you go out a little bit, you go down into Long Island, suddenly they start popping up."

On Salleh and Tucker's Two-Person Approach to Filmmaking

Matthew: "The main thing is the incredibly small footprint. It's basically just myself and Rose, and we do pretty much the whole movie. So I direct and Rose produces. I do the shoot. I do the cinematography. Rose does the sound. We both edit it. We do a surround-sound mix and picture work on the film in our one bedroom apartment."

Rose: "In the room we're sitting at now."

Matthew: "We just basically do the whole film from a technical point of view by ourselves. And, one, it makes it cheaper and more versatile — but the most-important thing is that versatility in that we don't need to have bosses that we get approval from when we come up with an idea, and we can just stay in a place until we get the story, and we can move around and be this very intimate film crew.

When we film, it's not this giant truck with 20 people turning up. It's me and Rose and a backpack. And that familiarity that people have with us it just gives a gives our film something else, I hope."

On How Having Such a Small Filmmaking Footprint Helps Get Subjects Onboard

Rose : "We love the intimacy that we can create with it just being the two of us. The fact that we're a couple as well, I think a lot of the people we're working with, a lot of people running these businesses are little husband wife teams as well.

So there's definitely a connection that we just have. We run our own business. We understand the challenges of running a small business, and we like to think we're quite entrepreneurial as well. I think we have a lot in common with the people who we are filming with."

Matthew: "When you run your own business, when you want to be sustainable and have your arts career that works as a business, you have to know as much about cinematography as you do about filing tax returns.

We met with a lot of people that had a passionate thing they wanted. I think instantly of Ed running Big Ed's BBQ, who had this passion for barbecue and then instantly realised he was in over his head — and that very much resonated with me as a person that got way in over my head when I decided to start a film company however many years ago.

That part of the storytelling also reminds me of my dad, who started his own business after working in government for many years. I think everyone that knows someone that's an entrepreneur, a sort of self-starter, it's a sort of crazy type of person. It was a lot of fun to hear those stories."

Rose: "But we definitely had to win people over. And we'd always have a few conversations over the phone before we turn up with cameras and really explain what we were trying to do. I think particularly in this day and age, people can be a little hesitant with documentary, like 'ohh, are you making fun of me or is this a hit piece?'.  And we would have to assure people that was not the case."

Matthew: "Something we weren't sure about: people operate their businesses and lives out of these former Pizza Huts, and it's kind of a humorous concept. I'm like 'do they think it's humorous as well?'. And they certainly did.

I remember our first phone call with everybody from the church in Boynton Beach that we filmed, and the first thing they wanted to tell us is that they'd given themselves a nickname of the Church of the Pepperoni. They think it's very funny as well.

There's something about that sense of humour, it's a little wry smile when they know that they run out of an old Pizza Hut. But then you go beneath that and you go look through the window, effectively, and there's these amazing lives, and these really powerful and interesting people.

I would say that with a lot of pop culture and nostalgia, people try to remember the old thing. But for us to be able to actually go into those buildings, it was fascinating that you have a really diverse set of people — and America's an incredibly diverse country — and all of these people had one thing in common: the floor plan of their businesses were exactly the same. And it was kind of odd.

A few months into filming, we'd be walking into like the fifth Pizza Hut and there'd be this weird déjà vu that would kick in — and I'd be like 'ohh, in Colorado, they put the door over that side, but I see you guys put it over here'. And there's this one bit where some of the old Pizza Huts, they always leak in the same spot — and they all go 'oh yeah, the leak'.

Maybe there's something comforting in knowing that people around the world might have a common experience with you, even though you will never meet them. So that was very powerful for us."

On the Research Process and Criteria for Picking the Former Pizza Huts Featured

Matthew: "There were a couple that we'd heard about. You start Googling, and lots of people have documented a lot of these old buildings. But only the building. It was hard to know anything more about it.

So we'd start with that process — it just started with conversations."

Rose: "I would dive in and take a look at a business. You can tell a lot from their social media and things like that. You can tell when a place is a community hub, and they were the places we were looking for. And honestly, I would just shoot them a message or an email, and get on the phone and chat.

I remember we called the owner of the Bud Hut in Colorado, and we talked to her for I think two hours. She was just so clearly so passionate and cared so much about her community, and we were like, 'well, that's an instant yes'."

Matthew: "This is something that we've always believed as a core part of the films we make, that everyone's got an interesting story to tell. So in a way, I wasn't even really worried, because I'm like 'well, everyone's got an interesting story to tell'. Our job is to listen and find those stories.

We try not to have too many preconceptions. We had ideas — as soon as we heard that there was a church down in Florida, we're like 'well that sounds amazing'. So there's ones like that.

One of the interesting ones was Taco Jesús, a Taco restaurant in in Lynchburg, Virgina — not necessarily a place known for its Mexican cuisine. But funnily, that restaurant didn't even exist when we started shooting the movie. We only shot that a few months ago because we were looking back over some notes, and one of them was something that was closed down."

Rose: "I have a list of addresses and every few months I would sweep through them just to see if a new place had popped up. I was looking at this place in Lynchburg, Virginia, which, after it was a Pizza Hut, it was a another pizza restaurant — and I noticed they were permanently closed. And I was like 'that's interesting, I wonder who's going in there?'. I did a little online research and realised it was going to be this brand-new taco restaurant, and it looked beautiful."

Matthew: "I think we saw a story that Jesús and his father-in-law were running it together, and I'm like 'there's a story that'. Then just your journalistic instincts kick in and you go 'oh, there's something interesting there'.

I think, to be honest, as we spoke to people, it confirmed more than anything that all these are really fascinating stories that we have to capture."

Rose: "There'll always be a few on the wishlist that we didn't get to, mainly just because we felt like we had a complete film. But there's always be the long list of places that maybe we could have visited — like there is a funeral home in Texas which would have been pretty interesting."

Matthew: "There's actually two."

Rose: "We could've kept filming forever."

Matthew: "It's interesting when we talk about when you're completely independent and you've got to do it yourself, how do you get started — but how do you finish? That's almost as much the challenging question and it's usually, with us, through exhaustion. Usually it's desperately editing into the night.

I remember with We Don't Deserve Dogs and a little bit with this film, you just stop eventually and go 'I think the movie is finished'. And you almost don't want to admit it's finished, because then you've got to work out what to do next. You've got to distribute and market the film, and all the rest of it.

But this one was definitely one where we had a lot of the film down, and then we took a bit of a break. Then we went and filmed with Taco Jesús, and we just slotted that in."

Rose: "It was the missing thing."

Matthew: "It was the different side of the story that brought it all together. So it's nice, it's been a lot of fun, because at the moment we're doing all the technical stuff, the sound and the music and all of that, and it's really lovely to be able polish up this thing that we've been putting together for a few years now."

On What You Learn About the US Today on a Cross-Country Road Trip That Examines How an Incredibly Nostalgic Symbol Has Been Reborn

Rose: "I think we managed to capture a pretty hopeful version of humanity. I'd like to think that. I think you realise that if you watch the news a lot …"

Matthew: "Which we all do."

Rose: "… which everybody does, there's maybe an impression of America and what middle America is like, and I think we wanted to challenge that expectation a little bit. There definitely are, I think, more good people than bad everywhere we went. We were met with open arms in communities of all shapes and sizes and political persuasions."

Matthew: "And we're just a bunch of hipsters from New York, so they should be very guarded.

But no, to be serious, I think it's this thing where we came in to listen and hear their story, and so we didn't come in with this ulterior motive of 'we want to set up the story'. That's been a really important thing about the films we do. We film with multiple subjects, multiple locations and people, and we don't have this scribbled-out script that we want to fit. We go where the story takes us. If the story revealed a much angrier America, then we would have gone 'okay, well, what is that story?'.

But for us, everyone was quite hopeful, quite proud — quite proud of being American, quite proud of their entrepreneurial side — which, by focusing just on that, was really interesting. We had this criteria for this movie: we want to meet people from all across America, but they have to be operating out of an old Pizza Hut restaurant. That limits you a little bit, and yet we found such diversity, such different people, different opinions, different lives, different stories.

So it was nice, even with such limitations on your sample size, you can still find a very diverse America."

Rose: "I think Mark from the Yupp's Karaoke in Fort Worth, Texas, puts it best: 'our diversity is our strength'. And this is coming from a bartender in Fort Worth, Texas. It's pretty beautiful stuff. "

Matthew: "I must admit that Yupp's Karaoke Bar was a lot of fun to film."

Rose: "It was raging on a Tuesday night. It was just packed. And from what I understand, they now have lines on Saturdays — you can't get in. They are going absolute gangbusters."

Slice of Life: The American Dream. In Former Pizza Huts . premieres at SXSW Sydney 2024, which runs from Monday, October 14–Sunday, October 20 at various Sydney venues. Head to the SXSW Sydney website for further details.

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The Effects of Sleep Quality on Dream and Waking Emotions

Francesca conte.

1 Department of Psychology, University of Campania L. Vanvitelli, Viale Ellittico 31, 81100 Caserta, Italy; [email protected] (O.D.R.); [email protected] (M.L.R.); [email protected] (G.F.)

Nicola Cellini

2 Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padova, Italy; [email protected]

3 Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy

4 Padova Neuroscience Center, University of Padova, Via Giuseppe Orus 2, 35131 Padova, Italy

5 Human Inspired Technology Center, University of Padova, Via Luzzatti 4, 35121 Padova, Italy

Oreste De Rosa

Marissa lynn rescott, serena malloggi.

6 Department NEUROFARBA, University of Firenze, Via di San Salvi 12, 50135 Firenze, Italy; [email protected] (S.M.); [email protected] (F.G.)

Fiorenza Giganti

Gianluca ficca, associated data.

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy reasons.

Despite the increasing interest in sleep and dream-related processes of emotion regulation, their reflection into waking and dream emotional experience remains unclear. We have previously described a discontinuity between wakefulness and dreaming, with a prevalence of positive emotions in wakefulness and negative emotions during sleep. Here we aim to investigate whether this profile may be affected by poor sleep quality. Twenty-three ‘Good Sleepers’ (GS) and 27 ‘Poor Sleepers’ (PS), identified through the Pittsburgh Sleep Quality Index (PSQI) cut-off score, completed three forms of the modified Differential Emotions Scale, assessing, respectively, the frequency of 22 emotions over the past 2 weeks, their intensity during dreaming and during the previous day. The ANOVA revealed a different pattern of emotionality between groups: GS showed high positive emotionality in wakefulness (both past 2 weeks and 24 h) with a significant shift to negative emotionality in dreams, while PS showed evenly distributed emotional valence across all three conditions. No significant regression model emerged between waking and dream affect. In the frame of recent hypotheses on the role of dreaming in emotion regulation, our findings suggest that the different day/night expression of emotions between groups depends on a relative impairment of sleep-related processes of affect regulation in poor sleepers. Moreover, these results highlight the importance of including sleep quality assessments in future dream studies.

1. Introduction

The interaction between sleep and affective brain function has received attention only in the last couple of decades. As pointed out by Walker and van der Helm [ 1 ], this delay appears surprising in light of two observations. On one hand, there is significant overlap between sleep physiology and the brain networks and neurochemical processes involved in affective modulation; in addition, sleep dysfunctions co-occur with remarkable frequency in most affective psychiatric disorders [ 1 ].

Despite the dearth of past research on the topic, recent work has begun to point out the importance of sleep for the regulation of emotions (see, e.g., [ 2 ] for a recent review). The role of sleep in affective processing is generally explained in light of the peculiar neurophysiology of sleep, and REM sleep in particular (see, e.g., [ 1 , 3 ]). In fact, this sleep state is associated with a relative deactivation of several areas of the neocortex [ 4 , 5 ], paralleling an increased activity in subcortical regions [ 4 , 6 ]. This pattern of activation, accompanied by the distinctive neurochemical balance occurring during REM sleep [ 7 , 8 ], is believed to provide optimal conditions for offline processing of emotional information.

In line with the prominent involvement hypothesized for REM sleep in emotional processing, the most recent theoretical approaches propose an important role of mental activity occurring during sleep (i.e., dreaming, according to Schredl and Wittman’s definition [ 9 ]) in these complex regulatory processes. At the biological level, it is supported by the existence of largely overlapping neural networks sustaining both (REM) dreaming and emotional processing (extensively reviewed in [ 10 ]). Indeed, several models propose that dreaming actively participates in the regulation of prior daytime emotions by facilitating the resolution of emotional conflicts [ 11 , 12 ], enhancing fear-extinction processes [ 3 ], and depotentiating the affective tone initially associated with waking events [ 1 ]. Another set of hypotheses focuses instead on the role of dreaming in optimizing affective reactions to future waking events: dreaming would allow an offline simulation of threatening or social episodes and a rehearsal of the corresponding threat- or social coping skills (respectively the “threat simulation theory” [ 13 ] and the “social simulation theory” [ 14 ]). Ultimately, both types of models converge in suggesting that waking and dream emotions are closely connected and that emotional processing occurring in dreams promotes adaptive behavioral responses to the challenges of waking life.

However, a clear understanding of the relationship between waking and dream emotions and their expression in subjective daytime consciousness and sleep mentation is still lacking. A recent study by our group [ 15 ] has addressed this issue in a sample of healthy adults: emotions of the last recalled dream, as well as those of the previous day and previous two weeks, were collected (through the modified Differential Emotions Scale, mDES [ 16 , 17 ]) and compared. Our findings mainly highlighted a discontinuity between waking and dream affect, with positive emotionality prevailing during the past two weeks as well as the day before the dream and reduced in the dream, while negative emotionality of the dream was similar to that of the preceding two weeks but significantly increased relative to the previous day. This interesting pattern of results opened the way to several hypotheses, such as the possibility that positive and negative emotions experienced in wakefulness may undertake different but parallel sleep-related regulation pathways.

As also suggested in the discussion of those findings [ 15 ], another intriguing hypothesis is that the relationships between waking and dream emotions (plausibly reflecting affective regulation processes) may be modulated by sleep quality. In fact, in the last couple of decades, a vast amount of research has focused on the effects of sleep disruption on several aspects of affective processing.

One night of sleep deprivation is sufficient to increase subjective reports of stress, anxiety, and anger in response to low-stress situations [ 18 ] and to increase impulsivity toward negative stimuli [ 19 ]. Moreover, after one night of sleep deprivation, subjects evaluated neutral pictures more negatively than control participants [ 20 , 21 ], independently of negative mood [ 20 ]. Impairments of emotion recognition [ 22 ] and expression [ 23 ] have been observed as well after single-night sleep deprivation.

Other studies provide evidence of emotional dysregulation following sleep deprivation using neural and physiological measures of emotionality. Enhanced amygdala reactivity in response to emotionally negative pictures, paralleled by a reduction of functional connectivity with medial prefrontal regions (believed to exert top-down regulatory control on the amygdala), has been detected after one night of sleep deprivation [ 24 ] as well as after five nights of sleep restriction [ 25 ]. Also, sleep loss has been shown to amplify pupil diameter responses during passive viewing of negative emotional pictures [ 26 ] and to increase sympathetic dominance of the autonomic nervous system, indexed by changes in heart rate variability [ 27 ].

An impact of sleep loss on affective processing has also been described in more ecologically relevant paradigms, i.e., based on cumulative sleep restriction protocols or on samples with impaired sleep quality. For instance, negative emotional changes have been reported in both adults [ 28 ] and adolescents [ 29 ] after several days of sleep restriction. Furthermore, poor subjective sleep quality has been associated with higher negative [ 30 , 31 ] and lower positive emotionality [ 30 , 31 , 32 ] and with decreased ability in cognitive reappraisal [ 33 ]. Habitual self-reported sleep quality has also been found to moderate the relationship between threat-related amygdala reactivity, negative affect, and perceived stress [ 34 ]. Furthermore, Tempesta et al. [ 21 ] showed that poor sleepers (classified through the Pittsburgh Sleep Quality Index, PSQI [ 35 ]) evaluated neutral pictures more negatively than good sleepers.

In sum, this brief review of data provides strong support to the idea that sleep disruption impairs affective regulation. In light of the aforementioned hypotheses on dreams as a reflection of ongoing emotional processing, dream emotions of individuals with disturbed sleep may represent an interesting object of study. The very few studies addressing this issue show that dreams of insomniacs [ 36 , 37 , 38 ] and narcolecptic subjects [ 39 ] are more negatively toned than those of good sleepers; also, nightmare frequency appears to be more elevated in individuals with poor sleep quality [ 40 , 41 , 42 , 43 ]. However, focusing exclusively on dream emotions, these studies do not allow the authors to make hypotheses on the possible differences between good and poor sleepers in emotion regulatory processes, which are probably better expressed in the relationships between waking and dream emotions rather than in dream emotions alone.

Indeed, several hypotheses on the presentation of waking and dream emotions in good and poor sleepers may be put forward. For instance, the profile of differences between daytime and dream emotionality observed in our previous study [ 15 ] could emerge in poor sleepers as well, indicating the presence of a similar pathway of affective processing notwithstanding the possible dysfunctionality of emotion regulation processes in poor sleepers observed in previous literature (e.g., [ 21 , 33 ]). Alternatively, poor sleepers could display an inverse pattern of emotionality in wakefulness and dreaming relative to good sleepers, with negative tone predominant in wakefulness and a positive rebound in sleep. Also, at variance with good sleepers, poor sleepers could manifest a more evenly distributed emotional tone (similar in both states of consciousness), and so on. The possibilities are multiplied when considering the time span over which these mechanisms unfold: for instance, each dream may process emotions experienced the day before, a few days before (in analogy with literature on the “dream lag” and “day-residue” effect [ 44 , 45 ]), or during wider daytime spans (e.g., the last few weeks, the general “time period”), etc.

Therefore, here we conduct an exploratory study to investigate the relationships between waking emotions and those of the subsequent night’s dreams in a sample of good and poor sleepers identified through the PSQI [ 35 ]. Specific aims of our study are:

• to compare, between good and poor sleepers, the prevalent emotional valence of the dream with that of the previous day and previous weeks;
• to assess the possibility that waking emotionality predicts dream emotionality in good and poor sleepers;
• to confirm findings from previous literature on dream emotional valence in good and poor sleepers using an instrument, the mDES [ 16 , 17 ], which addresses a repertoire of emotions broader than the ones commonly used in dream literature.

2. Materials and Methods

2.1. participants and procedure.

Figure 1 displays the recruitment and selection process. Four hundred volunteers from the cities of Naples and Caserta (Italy) were screened through a brief ad-hoc interview to collect general demographic data and information on medical conditions and life habits. The interview was conducted via telephone by a psychologist from the Sleep Lab of the University of Campania. Two hundred and twelve healthy participants (163 F, 49 M; mean age: 25 ± 8 years) were thus selected for the study, according to the following inclusion criteria: age between 18 and 65 years; absence of any relevant somatic or psychiatric disorder; absence of any sleep apnea or respiratory disorder symptoms; having a regular sleep–wake pattern; absence of sleep disorders; no history of drug or alcohol abuse; limited caffeine (no more than 150 mg caffeine per day, corresponding to about three cups of espresso or one cup of American coffee) and alcohol (no more than 250 mL per day) consumption.

Flowchart of the participant recruitment and selection process.

The whole selected sample ( N = 212) participated in a larger study [ 15 ], which included a validation of the Italian version of the mDES [ 16 , 17 ]. Thus, two forms of the questionnaire (WAKE-24 h and WAKE-2 weeks, assessing the frequency of specific emotions over the past 2 weeks and their intensity in the past 24 h, respectively) were administered to participants along with the Mannheim Dream Questionnaire (MADRE [ 46 ]) to collect data on dream recall frequency and several variables related to dreams, and the PSQI [ 35 ], in its Italian version [ 47 ], to assess habitual subjective sleep quality.

Of the 212 participants included in the validation study, 50 (38 F, 12 M; mean age: 24.6 ± 6.4 years) volunteered to take part in a second phase of the study, i.e., the assessment of relationships between waking and dream emotions. Participants received 10 copies of the WAKE-24 h mDES, with the instruction to complete one each night at bedtime, referring to the emotions experienced during that particular day. This had to be done until the day they recalled a dream. On the morning they recalled a dream, they had to fill in the DREAM mDES, specifically referring to the emotions experienced during the dream. Data collection was thus ended as soon as the mDES ratings of one dream were provided by each participant.

While our previous study [ 15 ] focused on differences between waking and dream emotions in the general sample, this study analyses the same dataset with regard to sleep quality, i.e., by dividing the final sample ( N = 50) into a group of ‘Good Sleepers’ and a group of ‘Poor Sleepers’ (GS and PS, respectively) based on the PSQI cut-off score (scores ≥ 5 indicate poor sleep quality [ 35 ]).

2.2. Instruments

• Italian version of the mDES: The original mDES [ 16 , 17 ] consists of 20 items corresponding to 20 different emotions (10 positive and 10 negative) whose intensity over the past 24 h is rated on a five-point Likert scale (from 0 = Not at all, to 4 = Extremely). Each category is described by three adjectives (e.g., “Grateful, appreciative, or thankful”): for clarity purposes, throughout the manuscript the noun referring to the first of the three adjectives will be used to identify specific emotion categories (e.g., “Gratefulness”). The Italian version [ 15 ] includes two additional positive emotions (“sexual/desiring/flirtatious” and “sympathy/concern/compassion”), which were included in the earlier version of the instrument [ 16 ]. In addition to this standard version (labeled WAKE-24 h mDES [ 15 ]), two other forms of the scale were developed in our previous study [ 15 ], assessing, respectively, the frequency of each emotion over the past two weeks (WAKE-2 weeks mDES) and the intensity of emotions experienced during the last recalled dream (DREAM mDES). The specific instructions provided in the DREAM and the WAKE-24 h mDES versions are: “Please think back to how you have felt during your last recalled dream/last 24 h. Using the 0–4 scale below, indicate the greatest amount that you’ve experienced each of the following feelings.” As for the WAKE-2 weeks form, the instructions are: “Please think back to how you have felt during the past two weeks. Using the 0–4 scale below, indicate the frequency with which you’ve experienced each of the following feelings.” (from 0 = Never, to 4 = Very frequently). The mDES also allows the use of aggregate measures of positive and negative emotionality (the Positive Affect (PA) and Negative Affect (NA) subscales, i.e., average scores of the positive and negative emotion items, respectively), which have shown to have high internal reliability, ranging from 0.82 to 0.94 [ 48 , 49 ]. The scale has been validated on the Greek [ 50 ] and Italian [ 15 ] populations and has shown to have good psychometric properties in its various translations [ 15 , 50 , 51 , 52 , 53 ].
• PSQI [ 35 ]: This questionnaire assesses sleep quality and disturbances over a 1-month time interval. It consists of 19 individual items which generate seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction. The sum of scores for these seven components yields one global score, ranging from 0 to 21, with 5 as a cut-off score which allows to differentiate good from poor sleepers [ 35 ] (higher scores indicate worse sleep quality). Here we use the Italian version of the PSQI [ 47 ], which has been validated on the Italian population [ 47 ].
• MADRE questionnaire [ 46 ]: This questionnaire measures several variables related to dreams such as frequency of dream recall, nightmares and lucid dreaming, attitude towards dreams and the effects of dreams on waking life. We report frequency of dreams, lucid dreams, and nightmares, as well as intensity of the dream experience, attitude towards dreams and correlates of dreams (the sum of items 13-14-15-16-17), all referring to how the contents of dreams are used in terms of problem solving and creativity (see [ 54 ]).

2.3. Data Analysis

Differences between GS and PS in age, gender distribution and MADRE scores were assessed using independent t -test, χ 2 (for categorical data) and Mann–Whitney test (for ordinal data). To assess the differences between groups in emotional valence of dreams and previous wakefulness, we conducted a 2 (Group: GS, PS) × 3 (Condition: WAKE-2 weeks, WAKE-24 h, DREAM) mixed ANOVA, with Δ mDES score (PA minus NA, i.e., an aggregate measure of valence, with positive values indicating positive valence and negative values indicating negative valence) as dependent variable. We used η 2 p as a measure of effect size and the Holm test for post-hoc analysis.

Also, in order to explore the potential predictors of dream emotions, we conducted, separately for GS and PS, a linear regression with DREAM Δ scores as dependent variables and WAKE-2 weeks and WAKE-24 h Δ scores as predictors. For each significant predictor, we reported the unstandardized (b) and the standardized (β) coefficient. All analyses were conducted using JAMOVI 1.2.27 and a p < 0.05 was considered statistically significant.

3.1. Descriptives

The sample was made up of 38 females (76%) and 12 males (24%), with an age range of 19 to 52 years.

A total of 50 DREAM mDES and 50 WAKE-2 weeks mDES (one per participant) were collected. As for the WAKE-24 h version, 84 scales were collected in total (50 referring to the day immediately preceding the dream and the remaining referred to the previous days); in fact, 30 participants (60%) recalled a dream after 1 night, 6 participants (12%) after 2 nights, and the remaining 14 (28%) after 3 nights. Only the 50 WAKE-24 h mDES scales (one per participant) referring to the day before the recalled dream were included in data analyses.

Twenty-seven participants (54% of the sample) reported a PSQI > 5 and were thus classified as PS [ 35 ], while the remaining 23 subjects (46%) made up the GS group. GS and PS were similar in terms of age (GS: 25.26 ± 7.39 vs. PS: 23.96 ± 5.04, t = 0.734, p = 0.466, Cohen’s d = 0.21) and gender distribution (GS: 5 M, 18 F vs. PS: 7 M, 20 F, χ 2 1 = 0.119, p = 0.730), while they significantly differed in PSQI scores (GS: 3.70 ± 0.92 vs. PS: 7.93 ± 1.83, t = −10.496, p < 0.001, Cohen’s d = −2.837).

3.2. MADRE Scores in Good and Poor Sleepers

The two groups showed similar dream frequency (median = 4, W = 301, p = 0.858), intensity of the dream experience (median = 2.5, W = 307.5, p = 0.959), attitude towards dreams (median = 2.4, W = 703.5, p = 0.770) and correlates of the dream experience (mean = 11, W = 286.5, p = 0.647). A significant difference was observed for the frequency of lucid dreams (W = 194.5, p = 0.023), with higher frequency in PS (median = 4) compared to GS (median = 3). The frequency of nightmares was nominally higher (W = 224.5, p = 0.091) in PS (median = 3) relative to GS (median = 4).

3.3. Characterisctics of Dream Emotions

3.3.1. good sleepers.

In GS, scores at the PA and NA subscales of the DREAM mDES showed a higher intensity of negative emotionality in the dream (PA: 0.80 ± 0.58 vs. NA: 1.40 ± 1.30; t22 = −2.29, p = 0.032, Cohens’ d = −0.48).

Looking at the specific emotions, all dreams contain at least 8 emotions and all of the 22 emotions are reported at least once. On average, GS reported 12.08 ± 4.79 dream emotions. As displayed in Figure 2 , the most frequent emotion is Sadness (reported by 91.3% of the participants), followed by Fear (82.6%) and Anger (78.3%), while the least frequent are Sensuality (30.4%) and Inspiredness (30.43%).

Proportion of Good Sleepers reporting each of the 22 emotions during the dream.

The most intensely experienced emotions during the dream were mostly negative ( Figure 3 ): Sadness (2.00 ± 0.28) was followed by Fear (1.87 ± 1.32), Stress (1.878 ± 1.28), Anger (1.70 ± 1.40), and Awe (1.61 ± 1.12).

Scores of each emotion in the WAKE-2 weeks, WAKE-24 h, and DREAM mDES in Good Sleepers. Panels ( a , b ) display positive and negative emotions, respectively. Error bars represent standard error of the means.

3.3.2. Poor Sleepers

Scores at the PA and NA subscales of the DREAM mDES did not differ (PA: 1.10 ± 0.76 vs. NA: 1.13 ± 0.81; t26 = −0.10, p = 0.925, Cohens’ d = −0.02), indicating an equal intensity of positive and negative emotionality in the dreams of PS.

As for specific emotions, all dreams contain at least 5 emotions and all of the 22 emotions are reported at least once. On average, PS reported 12.63 ± 4.39 dream emotions. As displayed in Figure 4 , the most frequent emotion is Awe (reported by 81.5% of the participants), followed by Pride (77.8%) and Solidarity (74.1%), while the least frequent are Gratefulness (37.04%) and Sensuality (29.6%).

Proportion of Poor Sleepers reporting each of the 22 emotions during the dream.

Although PA and NA scores did not differ, the most intensely experienced emotions during the dream were mostly negative ( Figure 5 ): Awe (1.74 ± 0.22) was followed by Anger (1.55 ± 0.25), Sadness (1.52 ± 0.26), Fear (1.48 ± 0.27), and Stress (1.41 ± 0.27).

Scores of each emotion in the WAKE-2 weeks, WAKE-24 h, and DREAM mDES in Poor Sleepers. Panels ( a , b ) display positive and negative emotions, respectively. Error bars represent standard error of the means.

3.4. Differences between Waking and Dream Emotions in Good and Poor Sleepers

The ANOVA on Δ mDES scores yielded a significant main effect of condition (F 2,96 = 15.41, p < 0.001, η p 2 = 0.24), with a decrease of delta scores (i.e., more negative emotionality) in the DREAM compared to WAKE-2 weeks and WAKE-24 h (all p holm ’s < 0.001), and no difference between WAKE-2 weeks and WAKE-24 h (p holm = 0.923). Although we did not find a main effect of Group (F 1,48 = 0.40, p = 0.528, η p 2 < 0.01), we observed a significant Group × Condition interaction (F 2,96 = 4.72, p = 0.011, η p 2 = 0.09, Figure 6 ): only GS displayed a reduction of delta scores from wakefulness to dream (WAKE-2 weeks vs. DREAM: p holm < 0.001; WAKE-24 h vs. DREAM: p holm < 0.001), while PS did not show any significant change (all p holm ’s > 0.644). No between-groups differences were observed in any of the three conditions (all p holm ’s > 0.643, Table 1 ).

Change in Δ mDES scores (PA minus NA) as a function of condition (WAKE-2 weeks, WAKE-24 h, and DREAM) in Good and Poor Sleepers. The orange area indicates positive affect and the blue area indicates negative affect. Error bars represent standard error of the means.

Mean and standard error of Δ scores in the two groups across conditions.

3.5. Predictors of Dream Emotional Valence (Δ mDES Scores) in Good and Poor Sleepers

In GS, linear regression analysis showed that neither WAKE-2 weeks nor WAKE-24 h Δ scores were predictive of DREAM Δ scores (F 2,20 = 0.04, p = 0.952, Adj. R2 < 0.01). The same result was observed in PS (F 2,24 = 0.99, p = 0.387, Adj. R2 < 0.01).

4. Discussion

This study investigated the relationships between dream emotions and those experienced during the previous days (both the day before the recalled dream and over the two weeks preceding it) in good and poor sleepers. In the frame of theoretical models on the role of dreaming in emotion regulation, postulating a close link between waking and dream emotionality, we aimed to assess the influence of poor sleep quality on this relationship. In fact, though previous literature has already shown the prevalence of negatively toned dreams in populations with disturbed sleep, we believe that affect regulation processes are plausibly better expressed in the interplay between waking and dream emotions rather than in dream emotions alone.

4.1. Proportion of Good and Poor Sleepers

Before discussing our main results, it is worth commenting on the high proportion of poor sleepers that emerged in our sample (54%). Considering that most of our participants were university students (mean age: 24.6 ± 6.4 years), this result is in line with those of several wide survey studies assessing the prevalence of poor sleep quality through the PSQI on similar populations and age groups. Indeed, the proportion of poor sleepers was over 40% in Mah et al. [ 55 ] and exceeded 60% in Lund et al. [ 56 ] and Becker et al. [ 57 ].

4.2. Results from the MADRE Questionnaire in Good and Poor Sleepers

Data from the MADRE questionnaire show that GS and PS are similar in most dream related variables, including dream frequency, intensity of dreams, attitude towards dreams, and perceived effects of dreams on waking life problem solving and creativity skills. However, PS show a higher frequency both of nightmares and lucid dreams. As for nightmares, this finding is consistent with previous studies showing increased nightmare frequency in poor sleepers [ 40 , 41 , 42 , 43 ]. Also, lucid dreaming has sometimes been associated with disrupted sleep [ 58 , 59 ]. Interestingly, nightmares and lucid dreaming have been conceptualized as belonging to a common domain involving unusual cognitions and perceptions in wakefulness and sleep [ 60 ], which would be linked to arousal and hypervigilance intruding in the sleep state [ 58 , 61 ] and thus could be viewed as indicators of poor sleep quality [ 58 ]. In other words, these hypotheses point to the existence of a close link between the quality of physiological sleep features and that of subjective sleep mentation.

4.3. Frequency and Valence of Dream Emotions in Good and Poor Sleepers

GS and PS reported on average a similar number of dream emotions (slightly more than 12), suggesting that the average amount of emotions (12.38) found in our previous study on the whole sample [ 15 ] was not affected by sleep quality. The number of emotions in our two samples is slightly higher than that reported in previous literature using the same self-report scale [ 62 ], probably because of methodological differences (see [ 15 ]).

As for emotional valence, GS displayed higher negative than positive emotionality (scores at the NA subscale) in the dream, whereas, in PS’ dreams, positive and negative emotionality appeared with equal intensity (no difference between PA and NA scores of the DREAM mDES). This finding well accounts for the one emerged in our previous study [ 15 ], in which NA scores were slightly higher than those at the PA subscale, but the difference failed to reach significance. The higher negative affect observed in GS is coherent with the finding that specific negative emotions were the most frequent as well as the most intense in this sample; also, it is in line with several previous studies showing a prevalence of negative emotions in dreams (e.g., [ 63 , 64 , 65 , 66 ], but see also [ 67 ] for a discussion on the differences between self and external ratings of dream emotions). Instead, the evenly distributed emotional tone observed in PS’ dreams apparently contradicts existing literature on populations with sleep impairments [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ], which points to more negatively toned dreams in these individuals. However, our analysis of specific emotions showed that, although positive emotions were the most frequently reported by PS, their negative emotions were the most intense. In addition, it must be considered that: (a) the instrument we used is quite different from those commonly used in dream research, since it includes a much broader repertoire of emotions and a more balanced number of positive and negative items, thus reducing the risk of underestimating the presence of positive emotionality; (b) results obtained on sleep disordered populations [ 36 , 37 , 38 , 39 ] are not fully comparable to those observed in healthy samples reporting poor sleep quality; (c) the higher frequency of nightmares observed in individuals with poor sleep quality (both in our present study and in previous research [ 40 , 41 , 42 , 43 ]) does not necessarily imply that their dreams are generally more negatively valenced (in fact, emotionality may be viewed as a “tonic” feature of sleep mentation, while nightmares, or lucid dreams, may be better conceptualized as “phasic” events, although the notion of a continuum between bad dreams and nightmares is sustained by several authors [ 68 , 69 ]).

4.4. Relationships between Waking and Dream Emotions in Good and Poor Sleepers

The main finding of our study is the difference observed between GS and PS in the profile of waking and dream emotionality. While GS display a striking inflection of emotional tone from wakefulness to the dream (i.e., affective tone is prevalently positive both during the previous weeks and the previous day and becomes extremely negative in the dream), PS’ emotionality remains stable across conditions. Specifically, in PS, differences between positive and negative emotionality (i.e., delta values) are very close to zero in all three scales.

First of all, this pattern of data suggests that habitual sleep quality significantly affects the interplay of emotional expression across wakefulness and dreaming. This observation is particularly important in light of the numerous discrepancies existing in data on dream features and especially dream emotionality (see [ 62 , 67 , 70 ]). Controversial results in this field are usually explained through methodological biases as well as biases linked to the retrospective nature of dream descriptions [ 62 , 67 , 70 ]. Our data prompt us to consider sleep quality as an additional factor affecting dream emotional experience, and thus able to confound results when not controlled for. Therefore, we believe that future dream investigations should include assessments of sleep quality even when addressing nonclinical samples.

At the theoretical level, the differences observed between GS and PS appear to reflect a different functionality of sleep–wake emotion regulation processes, in line with the recent models on dream-related affect regulation [ 1 , 3 , 11 , 12 , 13 , 14 ]. In other words, the lack of oscillations in prevalent emotional valence of PS (expressed by their flattened curve of Δ mDES scores across daytime and sleep) may depend on a relative impairment of their emotion regulation processes, whose effectiveness would instead be expressed by the opposite emotional tone in wakefulness and dreams of GS. Specifically, GS display a prevalence of positive affect during daytime and negative affect during the dream. As suggested in Conte et al. [ 15 ], the negative emotions experienced more frequently or intensely in the general period in which the dream occurs would be those in need of regulation during sleep, whereas positive emotions, requiring less modulation, would be underrepresented in the dream. Also, the predominant positive affect observed during wakefulness in GS would at least partly depend on effective sleep-related modulation that occurred in previous dreams. As for PS, they showed lower positive emotionality than GS both during the two weeks and the day preceding the dream (although the differences between groups did not reach significance). This observation is in line with past literature showing lower well-being and positive affect in poor sleepers [ 30 , 31 , 32 , 71 ], which also is plausibly linked to less effective sleep-related affect modulation. Moreover, as suggested above, the fact that negative affect does not prevail in PS’ dreams could indicate poor functioning of sleep-related emotion regulation.

A complementary explanation may also be proposed, referring to the recent hypothesis of a dream rebound of thoughts suppressed during wakefulness [ 72 , 73 , 74 ], which, in turn, can be traced back to Freud’s idea [ 75 ] that dreams reflect the return of mental contents inhibited during the waking hours. This kind of mechanism was plausibly active in GS, whose negative emotions, excluded from waking consciousness in favor of positive ones, may have rebounded in the dream. The process of negative affect suppression could instead have been ineffective in PS, possibly due to the fact that disrupted sleep is linked to deficits in higher cognitive functions including inhibition (e.g., [ 19 , 76 , 77 ]). In line with Malinowski et al. [ 78 ], who showed that successful suppression of thoughts and their rebound in the dream benefit the emotional response to pleasant and unpleasant thoughts, it may be hypothesized that, in good sleepers, the dream rebound of negative emotions reflects their effective processing in sleep, irrespective of the specific episodic memories (thoughts, events, etc.) that generated them.

In sum, our findings are probably the result of two parallel mechanisms: a general day-night emotion regulation process (with prevalent negative emotions of daytime being processed in sleep and thus reappearing in dreaming) and the specific suppression (either deliberate or automatic) of certain negative emotions during wakefulness with consequent rebound in the dream for regulation purposes.

It must be acknowledged here that our regression analysis on waking and dream delta scores did not yield significant results. In fact, emotional tone of the previous day and previous two weeks did not predict that of the dream in either group of participants. This result is consistent with three other studies which found few [ 79 ], small [ 80 ], or no correlations [ 81 ] between corresponding dream and previous daytime emotions. The absence, to date, of data on direct relationships between waking and dream affect does not lend support to our main hypothesis, i.e., the interpretation of our data in the frame of theories on dream-related emotion regulation [ 1 , 3 , 11 , 12 , 13 , 14 ]. However, clearer associations between waking and dream affect could exist across different time spans and in different directions than those investigated here and in the abovementioned studies [ 79 , 80 , 81 ]. In fact, as pointed out in the introduction, each dream could process emotions experienced the day before, a few days before (in analogy with literature on the “dream lag” and “day-residue” effect [ 44 , 45 ]), or during wider daytime spans (e.g., the last few weeks, the general “time period”, etc.). Also, as predicted by the “simulation models” [ 13 , 14 ], dream emotionality could reveal stronger associations with future rather than past waking affect, a possibility to be investigated in forthcoming studies.

Furthermore, it may be speculated that poor sleepers rate their dreams as less negatively toned compared to good sleepers also because of a different general perception of the dreaming experience. In other words, they could retrospectively evaluate their dream experience as more positive than it actually was since the simple fact of having dreamed, per se, represents for them a sign of having slept well (good sleepers would obviously have no such bias). This interesting possibility could be usefully investigated in future research.

Finally, our findings allow us to extend the discussion of our previous work on the same sample [ 15 ], by underlining the influence exerted by poor habitual sleep quality on waking and dream emotional expression. In fact, here we observed that the opposite prevalent emotional tone of wakefulness and dreams, emerged in the previous study, well describes GS’ profile, while PS display an equal amount of positive and negative affect in both states. The hypotheses made on these findings are coherent with the main interpretations discussed in our previous work. However, the current data allow us to exclude a couple of alternative explanations advanced on those data [ 15 ]. Specifically, we proposed that participants may have undergone some sort of social desirability effect in compiling the scales (see, e.g., [ 82 ]); in other words, they would have more easily identified positive emotions (coherent with a positive image of the self) in wakefulness and negative emotions in the dream (which is experienced as “involuntary”). Similarly, we acknowledged a possible recall bias linked to the time frame of events to which the emotions refer. In the DREAM mDES, the participant is focusing on a much shorter time frame compared to those of the daytime scales (2 weeks and 24 h). Among this limited pool of memories, the negative ones could appear more salient and thus be more easily recognized (according to the widely held tenet in psychology that “bad is stronger than good” [ 83 ]). While these two hypotheses may have applied to our GS group, we see no reason why PS would not have equally undergone these types of biases: thus, the different emotional profile emerged in the latter group induces us to rule out these possibilities.

4.5. Limitations

Our results should be considered in light of some limitations to be overcome in future research. The main limitation is the use of a self-report measure of sleep quality rather than standard polysomnography for the identification of good and poor sleepers. However, it must be noted that groups of good and poor sleepers classified through the PSQI have been shown to significantly differ in polysomnographic sleep measures in several previous studies [ 35 , 84 , 85 ].

Furthermore, according to some authors [ 67 , 86 ], self-ratings of dream emotions based on emotion rating scales may be biased by demand characteristics of the rating task (i.e., individuals may be primed by answer options) or phenomena such as the positivity offset (i.e., the tendency to experience mildly positive mood most of the time); still, several authors argue that self-ratings more validly represent dream emotional experiences [ 65 , 87 ].

5. Conclusions

In conclusion, to the best of our knowledge, this is the first study to investigate differences between good and poor sleepers in the profile of emotionality across wakefulness and dreaming. Overall, our findings show that good sleepers experience a notable change in emotionality between wakefulness and dreaming, with a prevalence of positive affect during daytime and predominant negative affect during dreaming, whereas poor sleepers are characterized by equal intensity of positive and negative emotionality in both states. In the frame of recent theoretical models postulating a role of dreaming in affect regulation, the lack of changes in prevalent emotional valence across states observed in the latter group may be interpreted as reflecting ineffective sleep-related emotional processing. Furthermore, regardless of the theoretical framework, our results highlight that sleep quality is associated with notable differences in the expression of waking and dream emotions which should not be neglected in future dream research. Therefore, our findings definitely encourage researchers to include sleep quality assessments in dream studies (both on clinical and nonclinical samples) and prompt future investigations on sleep-impaired populations as a privileged object of study in the field of research on dreaming and emotion regulation processes.

Author Contributions

All authors contributed in a meaningful way to this manuscript. Conceptualization, F.C., F.G. and G.F.; Methodology, F.C. and G.F.; Formal analysis, N.C. and O.D.R.; Investigation, O.D.R. and S.M.; Writing—original draft preparation, F.C. and N.C.; Writing—review and editing, F.C., M.L.R. and G.F.; Visualization, F.C. and N.C.; Supervision, F.G. and G.F.; Project administration, F.C., F.G. and G.F. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Institutional Review Board Statement

The study design was submitted to the Ethical Committee of the Department of Psychology, University of Campania “L. Vanvitelli”, which approved the research (code 1/2017) and certified that the involvement of human participants was performed according to acceptable standards.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

Conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Taku Fukui Artificial Intelligence Laboratory

In at the deep end – straight into an assignment on joining Fujitsu Research!

Straight after joining Fujitsu Kyushu Network Technologies Limited, I was seconded to Fujitsu Research, where I was assigned to work on the development of eye tracking technology ( *1 ), which estimates where people are looking. This technology had many diverse application requests from customers, including detecting distracted drivers and driver drowsiness, as well as behavior analysis in retail stores. However, in the early stages of development, we faced significant challenges as the accuracy was initially very low. We attempted to estimate gaze direction by detecting pupils from video footage. However, pupils shrink in bright light and reflections from eyeglass lenses obscure visibility, presenting numerous detection challenges. First, we purchased a device to fix the position of the face, and while maintaining a constant relationship between the camera and the face position, we systematically isolated the causes of inaccuracies one by one. As a result of these efforts, we eventually achieved high accuracy and it was immensely satisfying to present our achievements at various exhibitions and receive positive reactions and feedback from customers.

Committed to a career in research

After completing my secondment, I returned to my original company and resumed daily work in program development. Among various projects, one notable one involved the development of a satellite image difference detection program. In remote mountain areas, illegal dumping and logging were occurring, representing a major workload for local government patrols. By comparing past and current images, we could detect changes without physically visiting the site, enabling prompt action. I was responsible for helping to develop the image difference detection program. While I found fulfillment in such programming-focused development tasks, I realized I yearned for the excitement of developing novel technologies. With over a decade of engineering experience, I found myself wanting to make a change and engage directly in research. Consequently, I made the decision to transfer to Fujitsu Research.

Eliminating hallucinations in generative AI

Currently, I am researching the detection and suppression of hallucinations in generative AI at our Artificial Intelligence Laboratory. While generative AI has made rapid advances, the phenomenon of hallucinations represents a significant barrier to its widespread adoption. These are outputs that seem plausible but are based on errors that are not grounded in fact or established knowledge. Many voices express concerns that these hallucinations prevent the confident use of generative AI in a business context. For example, if an image of a person riding a bicycle is inputted into a generative AI system and it is asked, "Is this person violating traffic laws?", the AI might answer "No." However, upon reviewing the image, it could be seen that the bicycle was actually being ridden on a sidewalk where cycling is prohibited. In such cases, it's necessary to analyze where the generative AI has misjudged the situation and what it overlooked. If the AI did not focus on the person riding the bicycle, it's likely to be a hallucination. My focus is on meticulously analyzing how generative AI arrives at its responses, then implementing measures to detect the basis of its judgments and suppress incorrect answers. Establishing technologies for detecting and suppressing hallucinations in generative AI will enable its safe and confident use in professional applications.

Valuing a process that generates results

Several years ago, during a challenging period at work, I came across a book titled "Yes! You Can Be Absolutely Lucky!" It is all about imparting a positive mindset to believe that luck can be seized, and that achieving dreams involves understanding mechanisms and strategies. Our mindset can change our lives — thinking negatively can attract negativity, while focusing on positive aspects gradually transforms everything for the better. By changing my perspective, I learned to approach life with optimism, greatly improving my outlook during difficult times. This book has been a source of profound help and inspiration to me on many occasions, and underlines how discovering something like this book during a time of adversity can significantly alter one's life.

As we work towards creating a prosperous society, it is true to say that sometimes the work itself isn't always enriching. Many people struggle and face mental challenges. We often focus on the value of outcomes and outputs, but it's crucial also to acknowledge the process that leads to those results. However we reach a given outcome, it’s equally important to enjoy the process, or feel a sense of security. I believe that it’s not just a question of producing good results, but also essential to consider the emotions and experiences of stakeholders in order to make one’s working hours the best experience possible.

Energizing oneself with walks and travel

The move to teleworking has reduced my physical activity, and so I've started waking up a bit earlier every morning to go walking. There are rice fields around where I live, and it’s truly refreshing to go out walking while feeling the changing seasons, setting perfect tone for the day. Additionally, on weekends, I go out with my family or travel. During this year's golden week, I went to Shikoku in Japan with my wife and child, and we were able to relax and enjoy our time together. I look forward to traveling so much that as soon as one trip ends, I start planning the next! It’s about achieving a balance, cherishing values that are important to me on the one hand such as health, my family, and societal contribution, while continuing my R&D endeavors on the other.

Editor's note

In addition to the research mentioned in the article, Taku is also engaged in R&D on the integration of knowledge graphs and large language models (LLMs) ( *2 ). One of the challenges of generative AI is that its responses can sometimes be inaccurate. However, LLMs that utilize knowledge graphs can better understand the relationships within business knowledge, thereby improving response accuracy. It is anticipated that the application of LLMs will advance in fields such as law, finance, and healthcare. People will be freed from having to read and organize large volumes of text, leading to a more fulfilling life. (Xiang Yi Peck, Technology Strategy Unit)

• (*1) Eye Tracking Technology
• (*2) Fujitsu chosen for GENIAC project, starts development of large language models for logical reasoning
• Notes (*1) only available in Japanese

Titles, numerical values, and proper nouns in this document are those reported when this interview was made.

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