loftus and palmer experiment summary

Loftus and Palmer (1974): Car Crash Experiment

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Psychologist Elizabeth Loftus has been particularly concerned with how subsequent information can affect an eyewitness’s account of an event.

Her main focus has been on the influence of (mis)leading information regarding both visual imagery and wording of questions concerning eyewitness testimony.

A  leading question  is a question that suggests what answer is desired or leads to the desired answer.

Loftus’ findings indicate that memory for an event that has been witnessed is highly flexible.  If someone is exposed to new information during the interval between witnessing the event and recalling it, this new information may have marked effects on what they recall.  The original memory can be modified, changed or supplemented.

The fact that eyewitness testimony can be unreliable and influenced by leading questions is illustrated by the classic psychology study by Loftus and Palmer (1974), Reconstruction of Automobile Destruction, described below.

To test their hypothesis that the language used in eyewitness testimony can alter memory.

Thus, they aimed to show that leading questions could distort eyewitness testimony accounts and so have a confabulating effect, as the account would become distorted by cues provided in the question.

To test this, Loftus and Palmer (1974) asked people to estimate the speed of motor vehicles using different forms of questions.

Estimating vehicle speed is something people are generally poor at, so they may be more open to suggestions.

Experiment One:  5 verbs in leading questions

Forty-five American students from the University of Washington formed an opportunity sample.

This was a laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design ).

Seven films of traffic accidents, ranging in duration from 5 to 30 seconds, were presented to each group in random order.

After watching the film, participants were asked to describe what had happened as if they were eyewitnesses.

They were then asked specific questions, including the question “About how fast were the cars going when they (smashed / collided / bumped / hit / contacted) each other?”

Thus, the IV was the verb of the question, and the DV was the speed reported by the participants.

The estimated speed was affected by the verb used. The verb implied information about the speed, which systematically affected the participants’ memory of the accident.

Participants who were asked the “smashed” question thought the cars were going faster than those who were asked the “hit” question.

The participants in the “smashed” condition reported the highest speed estimate (40.8 mph), followed by “collided” (39.3 mph), “bumped” (38.1 mph), “hit” (34 mph), and “contacted” (31.8 mph) in descending order.

The results show that the verb conveyed an impression of the speed the car was traveling and this altered the participants” perceptions.

In other words, eyewitness testimony might be biased by the way questions are asked after a crime is committed.

Loftus and Palmer offer two possible explanations for this result:

• Response-bias factors : The misleading information provided may have influenced the answer a person gave (a “response-bias”), but didn’t actually lead to a false memory of the event. For example, the different speed estimates occur because the critical word (e.g., “smash” or “hit”) influences or biases a person’s response.
• The memory representation is altered : The critical verb changes a person’s perception of the accident—some critical words would lead someone to perceive the accident as more serious. This perception is then stored in a person’s memory of the event.

If the second explanation is true, we expect participants to remember other details that are not. Loftus and Palmer tested this in their second experiment.

Experiment Two: The broken glass manipulation

A second experiment was conducted with the aim of investigating is leading questions simply create a response bias, or if they actually alter a person’s memory representation.

150 students were shown a one-minute film which featured a car driving through the countryside followed by four seconds of a multiple traffic accident.

Afterward, the students were questioned about the film. The independent variable was the type of question asked.

• 50 participants were asked “how fast were the car going when they hit each other?”,
• 50 participants were asked, “How fast were the cars going when they smashed each other?”
• the remaining 50 participants were not asked a question about the car’s speed (i.e., the control group).

One week later, the dependent variable was measured – without seeing the film again, they answered ten questions, one of which was a critical one randomly placed in the list:

“Did you see any broken glass? Yes or no?”

There was no broken glass in the original film.

Participants were asked how fast the cars were going when they smashed were more likely to report seeing broken glass.

This research suggests that questioning techniques easily distorts memory, and information acquired after an event can merge with original memory, causing inaccurate recall or reconstructive memory.

The results from experiment two suggest that this effect is not just due to a response bias because leading questions altered the participant’s memory for the event.

The addition of false details to a memory of an event is referred to as confabulation. This has important implications for the questions used in police interviews of eyewitnesses .

Consequently, Loftus and Palmer support the reconstructive memory hypothesis – arguing that information gathered at the time of an event is modified by data gathered afterward.

Over time, information from these two sources is integrated so that it is impossible to separate them—in effect, we have only one memory.

High level of control

Perhaps the greatest strength of Loftus and Palmer’s experiment is the degree of control over confounding variables . As the study was lab-based, the researchers could ensure that a range of factors (age of participants, incident viewed, environment, etc).

Consequently, they could ensure that these factors did not affect the respondents’ answers and that only the verb condition was causing the participants to reevaluate their memories.

Practical Implications

The reconstructive memory hypothesis is extremely useful as a psychological explanation, for instance, in formulating guidelines for police questioning witnesses and suspects.

The conclusion that leading questions can affect memory has important implications for interviewing witnesses , both by police immediately or soon after an event and also by lawyers in court sometime later.

Interviewers should avoid leading questions and be careful to word questions in a way that does not suggest an answer to the person they are interviewing.

The study also had real-world implications; based on evidence such as Loftus’s, the Devlin Report (1976) recommended that trial judges instruct juries that it is not safe to convict on a single eyewitness testimony alone.

A strength of the study is it’s easy to replicate (i.e. copy). This is because the method was a laboratory experiment which followed a standardized procedure.

Low ecological validity

One limitation of the research is that it lacked mundane realism / ecological validity. Participants viewed video clips rather than being present at a real-life accident.

As the video clip does not have the same emotional impact as witnessing a real-life accident, the participants would be less likely to pay attention and less motivated to be accurate in their judgments.

Furthermore, watching a real crash provides much more context—the participants were cued to watch the video, whereas crashes in real life are largely unexpected.

In an experiment, you may expect to be asked questions about what you are watching, which may make you attend the film differently.

In real life, the answers you give may have consequences, which may put pressure on the witness.

Overall, we can probably conclude that this laboratory experiment had low ecological validity and thus may not tell us very much about how people’s memories are affected by leading questions in real life.

Conflicting research

A study conducted by Yuille and Cutshall (1986) conflicts with the findings of this study. They found that misleading information did not alter the memory of people who had witnessed a real armed robbery.

This implies that misleading information may have a greater influence in the lab rather and that Loftus and Palmer’s study may have lacked ecological validity.

He was especially interested in the characteristics of people whom he considered to have achieved their potential as individuals.

Biased Sample

A further problem with the study was the use of students as participants. Students are not representative of the general population in several ways.

Differences between students and the broader population, such as age, memory abilities, learning habits, driving experience, and susceptibility to demand characteristics, could make it difficult to generalize the findings.

Importantly, they may be less experienced drivers and, therefore, less confident in their ability to estimate speeds. This may have influenced them to be more swayed by the verb in the question.

Demand Characteristics

Participants know they are in a laboratory experiment, which will affect their behavior in several ways. They will be looking for clues on how to behave (demand characteristics), and they will usually want to help the experimenters by giving them the results they think they want.

We cannot know that the leading questions had irretrievably altered the participants’ original memories.

Instead, participants could merely be following the researcher’s suggestions in both the original round of questions and the follow-up questions.

In effect, demand characteristics could be “carried forward” – as participants remembered being asked about the cars “smashing” into each other, they were prompted to say that they had seen broken glass in the follow-up study.

Independent Learning Tasks

• Draw a table showing the results of experiment one and draw a bar chart to show the results of experiment two.
• Read the original article of the study.
• Conduct your own study repeating one of the experiments by Loftus and Palmer.
• Use photographs (or video clips) of car accidents and write a set of questions, one of which will be the critical question.
• Test one group of participants using the “smashed” condition and the other group with the “hit” condition.
• Calculate the mean, median and mode speed estimates for both the “smashed” and “hit” conditions. Illustrate your results in either a table or graph.

Learning Check (1)

• Write an experimental hypothesis for experiment 1. Make sure it is clearly operationalized and include the independent and dependent variables.
• Why was it a good idea to ask 10 questions rather than just asking the critical question alone?
• Why was each group of participants shown the 7 video clips (of car accidents) in a different order?
• Outline the possible sampling technique that may have been used in this study.
• The participants knew they were taking part in a psychology experiment. How do you think this may have effected their behavior?
• Can you think of a way that this problem might of been overcome?

Learning Check (2)

• Write a null hypothesis for experiment 2. Make sure it is clearly operationalized and include the independent and dependent variables.
• What is a “control group”, and why is it necessary?
• What is an “experimental” group?
• Outline one difference between the responses given between the two experimental groups.
• Outline the quantitative measure used in this study.

Devlin Committee Report: Report of the Committee on Evidence of Identification in Criminal Cases, 1976 Cmnd 338 134/135, 42

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of auto-mobile destruction : An example of the interaction between language and memory. Journal of Verbal Learning and Verbal behavior , 13, 585-589.

Yuille, J. C., & Cutshall, J. L. (1986). A case study of eyewitness memory of a crime. Journal of Applied Psychology, 71(2), 291.

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Loftus and palmer (1974) – eyewitness testimony.

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of verbal learning and verbal behavior , 13 (5), 585-589.

This is the classic cognitive psychology study which you will look at for your H167 AS OCR Psychology exam. You will also need this study for your OCR H567 A Level Psychology core studies exam.

The theme of the cognitive psychology studies in the H167  exam is memory.  This study by Loftus and Palmer (1974) focuses on an applied area of memory: eyewitness testimony. 

In order to best understand this study, it is highly recommended that you first read the following books written by Elizabeth Loftus:

Eyewitness Testimony

The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse

What is eyewitness testimony?

Eyewitness testimony is a form of evidence used in the court systems. It relies on heavily on the memory of the eyewitness (person who saw an event) and until Elizabeth Loftus and colleagues started considering the reliability of memory, the court system assumed that the memory of eyewitnesses was highly accurate. We will see in this study and the further reading, how this might not be the case.

What theory is the research based on?

The research is based upon Barlett’s schema theory, which suggests that memories can be influenced by the previous knowledge of a person. For example, if I see something flying through the air, which is blue and quite small, but I can’t quite see what it is, and then someone asks me what I saw, I might reply it was a blue bird. In this example, I didn’t know exactly what I saw, but I used my previous knowledge to make a guess about what I saw. This is the idea what Loftus and Palmer’s research was based on: our previous knowledge knowledge influences our memory.

In the previous example about the blue bird, there was an interpretation of the information of the blue flying thing and it was recorded in memory as blue bird.

This example served to demonstrate some of the ways in which memory operates: by constructing and reconstructing information, based on what was observed and the previous information which we hold.

Aim of the Experiment

Method and design.

Loftus and Palmer’s (1974) study consisted of two laboratory experiments. Both experiments used an independent measures design, with the participant’s only taking part in a single condition.

Experiment 1

Independent variable: verb used in the critical question: “About how fast were the cars going when they ‘verb’ into each other?”

There were five different verbs used, all of which had different levels of intensity.

Dependent Variable: the participants’ estimate of the speed of the cars when the they collided.

Experiment 2

Independent variable: verb used in the question: “How fast were the cars going when they ‘verb’ each other?”

There were three conditions:

• Control group (this group was not questioned about the speed of the cars).

Dependent variable: Participants’ answer to the critical question: ‘Did you see any broken glass?’ (either: yes or no).

Sample and Sampling Method

The sample in experiment 1 consisted of 45 undergraduate psychology students from the University of Washington.

Experiment 2 

The sample in experiment 2 consisted of 150 undergraduate psychology students from the University of Washington.

Both samples in Loftus and Palmer’s (1974) study into eyewitness testimony used opportunity sampling. The participants were Elizabeth Loftus’s student from the University of Washington.

All 45 participants were shown the same seven film clips of different traffic accidents which were originally made as part of a driver safety film.

After each clip participants were given a questionnaire which asked them firstly to describe the accident and then answer a series of questions about the accident.

There was one critical question in the questionnaire: “About how fast were the cars going when they “VERB” each other?”

One group was given this question while the other four groups were given the verbs “smashed’, ‘collided’, ‘contacted’ or ‘bumped’, instead of ‘hit’.

All 150 participants were shown a one-minute video. During the video a four-second there was a 4-second multiple car crash.

They were then given a questionnaire which asked them to describe the accident and answer a set of questions about the incident.

There was a critical question about speed: – One group of 50 participants was asked, “About how fast were the cars going when they smashed into each other?” – Another group of 50 was asked, “About how fast were the cars going when they hit each other?” – The third group of 50 did not have a question about vehicular speed.

One week later, all participants, without seeing the film again, completed another questionnaire about the accident which contained the further critical question, “Did you see any broken glass – Yes/No?” There had been no broken glass in the original film.

The results in this experiment are the speed estimates of the participants after they had watched the video with the car crash and had been asked the critical question with one of the five verbs. The more inaccurate the participants’ estimate of the speed of the crash, the greater the memory distortion.

Here are the mean speed estimates for each of the five different verbs:

Smashed   40.5 mph

Collided 39.3 mph

Bumped  38.1 mph

Hit 34.0 mph

Contacted 31.8 mph

Loftus and Palmer (1974) suggest two possible reasons for these results. Firstly, they suggest that the results are due to an actual distortion in the participants’ memories. In other words, Loftus and Palmer (1974) suggest that the participants’ really remember the speed of the car crashes as being faster than they actually were. Secondly, Loftus and Palmer (1974) suggest that the results could in fact be due to a response bias, that is to say, the participant adjusted their estimate of the speed based upon the verb used and did not experience an actual distortion in their memory.

The results of experiment 2 are participants’ recollections of seeing broken glass in the video of the car crash. In the video, broken glass was not present. Therefore, any participant who recalled seeing broken glass may have had their memory distorted by the post-event information, that is, the verb used. If there were significantly more participants who recalled seeing broken glass in one condition compared with another, then we may determine that the results are due to the manipulation in the experiment or confounding variables.

Participants who saw broken glass: 

Smashed:  16

Control:  6   

Participants who did not see broken glass:

Smashed:  34

Control:  44  

These results are significant, which suggests that the experimenters manipulation did in fact cause the results.

Loftus and Palmer (1974) suggest there are two types of information which create memories. Information of an event and information after an event. They suggest these two sources of information work together to create the memory, which is what they suggest happened in their second experiment to lead some participants to believe that there was broken glass.

Conclusions

There are two kinds of information which contribute to the creation of memories: information gained during an event and information gained after the event. These two types of information may lead to a distortion of memories and even the creation of false ones. For example, seeing glass when there was in fact none.

Memory is not like a tape recorder. Human memory is susceptible to change and decay.

Small changes in information can cause distortions in memory.

Loftus and Palmer (1974) Evaluation

– Loftus and Palmer (1974) only consider two kinds of information which create memories: information about the event and information after the event. This may be an incomplete account of the information that goes in to creating memories, as they have not considered pre-event information, which may affect how individuals process the information of the event and the information after an event.

+ Laboratory study – the laboratory environment allows the researchers to control many aspects of the environment and experience of the participant, which reduces confounding variables and thus increases the internal validity of the study

– Ecological validity – the ecological validity in this study may be considered low because the study utilised laboratory experiments, which involved the participants watching videos of car crashes. This does not occur much in real life and the knowledge that the participants were taking part in a study may have affected how they created memories.

+ Application – Despite the low ecological validity in this study, we may find some ecological validity from the task which the participants were required to complete. They were asked, albeit with a questionnaire, about an event they had witnessed. This is very similar to how the police and court system addresses eyewitness testimony and thus this study has great applicablity for the criminal justice system, as it advises against the use of leading questions.

Further Reading

Psych Yogi’s Top Ten Psychology Revision Tips for the A* Student

• Experiments

The Loftus and Palmer Study on the Value of Speech

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Loftus and Palmer Summary

• Core studies
• Created by: avrilturner2610
• Created on: 06-05-22 10:51
• To test the hypothesis that the language used in eyewitness testimony can alter memory.
• Eyewitness testimony
• IV: verb used in the critical question "About how fast were the cars going when they ___ into each other?"
• DV: The participants estimate of the speed of the car.
• 7 videos of traffic incidents watched. Verbs: Hit, smashed, collided, bumped, contacted
• IV: verb used in the same question as experiment 1
• DV: Participants answer to the critical question "did you see any broken glass?"
• 3 conditions: Hit, smashed and control group (not asked speed of cars).
• Experiment 1: 45 American students from the university of Washington (5 groups of 9).
• Experiment 2: 150 American students from the university of Washington (3 groups of 50).
• Method and design : Lab experiment and Independent measures design.
• Experiment 1: Smashed = 40.8mph. Contacted = 31.8mph.

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