cobra experiment

Consumer Behavior

What the cobra effect teaches us about reward psychology, here's a cautionary tale about the psychology of rewards..

Updated February 23, 2024 | Reviewed by Ray Parker

• The cobra effect teaches us that rewards can easily backfire, especially if they're not correctly understood.
• The power of a variable reward is critical, as it can significantly impact a person's behavior.
• Use incentives strategically by understanding the tradeoffs between intrinsic and extrinsic motivation.

Few things can ruin your daily commute faster than a chance encounter with a venomous cobra. And if you lived in New Delhi during the early 1900s, this might happen to you regularly. The streets were rife with cobras during colonial rule, posing a major public safety threat to New Delhians.

The situation became so untenable that the colonial government sprang into action with what they thought was the perfect solution: Instead of the government going in and trying to regulate these pesky serpents, let's make it a team effort by offering cash rewards to anyone who captures and kills the snakes themselves.

This was a well-intentioned reward system , but it backfired spectacularly. And it wasn't merely because ordinary citizens were terrible at catching snakes, often harming themselves. Instead, it was the incentives themselves: Clever New Delhians quickly realized that the more snakes there were, the more money there was to gain. People began breeding cobras in order to turn them in and collect their reward.

What started as a system for eliminating the cobra population actually increased it.

This story has now become immortalized in the psychology of incentives and gave rise to what's known as the cobra effect . This now describes instances when an incentive system backfires and has the opposite effect on the intended behavior. It provides a cautionary tale to anyone looking to apply incentives and rewards to solve a problem.

The cobra effect also provides lessons for marketers. Understanding the psychology of motivation is crucial for driving consumer behavior . And as the British colonialists quickly learned, harnessing the power of incentives is not as straightforward as it always seems. We'll return to this issue of motivational backfire soon. But first, when and how do incentives work well ?

The Psychology of Rewards

At a basic level, incentives drive behavior through positive reinforcement. If you give your dog a treat when it sits on command, this rewards that behavior. It'll start sitting on command more and more, anticipating future incentives.

Simple enough. But what happens when you only reward your dog for this behavior "some" of the time? Is this better for motivating that behavior, or worse? If you're like most people, you'd predict this would be much worse. Consistency should be key. But you'd be wrong.

In a classic study, behavioral psychologist Michael Zeiler tested these reward schedules against each other. He and his research team placed pigeons in the same cage and placed them in front of two levers: The first delivered a consistent reward; every time the pigeon pressed it, he would receive a food pellet. The second was a variable reward: Each press wasn't guaranteed to deliver a pellet. Instead, these occurred in random trials roughly 60% of the time.

The results were shocking: The pigeons flocked to the lever that delivered the random incentives, spending nearly twice as much time with it. It turns out that pigeons love pellets, but they love random pellets even more.

This is the power of variable reward. And it's far from limited to pigeons and pellets. Experiment after experiment has shown that the most effective types of reward are those with a general expectation of reward but in which the actual reward comes at random and unpredictable times.

The variable reward is a key insight for marketers to understand. Providing incentives can drive consumer behavior, but this can be supercharged when these come at variable, unpredictable intervals. So, think about the kinds of behaviors you want to increase. This can be anything, from sharing a referral code to visiting a retail location. And think about the current rewards or incentives you currently implement at these junctures of the customer journey . Is there room to add a bit of variability and unpredictability?

There's a lot to say about harnessing the power of surprise. A word of caution, however, is that while variable reward reliably drives behavior, it doesn't necessarily drive positive evaluations for the brand. Social media platforms, for example, rely heavily on various variable rewards to keep consumers returning and staying longer. So consider both the impact on behavior as well as the overall state of the consumer.

Tradeoffs in the Psychology of Motivation

As we saw with the cobra effect, incentives can easily backfire. There is such a thing as "too much" motivation, which will make the behavior less likely. How can that be?

Motivation is complex. For any given behavior, there are multiple reasons why we did it. But these are broken down into two general categories: extrinsic motivation and intrinsic motivation. The most common form is extrinsic motivation; we engage in a behavior for some future reward. This can be anything. You go for a run because we want to improve our time. You post on social media because you want likes, attention , or followers.

But there's another kind altogether: intrinsic motivation. You engage in the behavior just because . If you go on a run just because you like it—irrespective of any future gains—this is intrinsic motivation. Artists who engage in their craft because of a love for their medium are deeply motivated by intrinsic reward. Some athletes play the game for money; for others, it's for the sheer love of the game. With all the awards, accolades, attention, and other extrinsic factors stripped away, you'd still engage in this behavior. That's intrinsic motivation .

And here's the thing: There's a major tradeoff between these two types of motivation. Research has found, for example, that when we're already intrinsically motivated to engage in a behavior, adding an extrinsic motivator actually decreases our likelihood of engaging with it. Many children, for example, are intrinsically motivated to draw. They'll draw, draw, and draw for the sheer enjoyment of it. So what happens when you offer to pay them $1 for every drawing? After a brief spike in frenetic production, the behavior slows to a halt.

This is known as the overjustification effect . And it isn't limited to children's art. It's a robust effect with all behaviors and activities: When you're already intrinsically motivated, applying extrinsic reward backfires and brings down the behavior.

This should give marketers much-needed caution when introducing rewards into the consumer experience. Extrinsic motivators are great at driving consumer behavior when there's a low level of existing passion for them. If a given consumer is already passionate and, therefore, intrinsically motivated to share your brand with friends, introducing a rewards program (which provides extrinsic motivation) will likely have a negative impact on their likelihood to do so. This is precisely the approach Tait Duryea, CEO of real estate investment firm for pilots Turbine Capital, takes with referrals,

“Instead of incentivizing referrals, we ask for ‘goodwill’ referrals. We take goodwill referrals as a sign of intrinsic motivation from our customers and a signal showing our client-centric approach is working."

Final Thoughts on the Psychology of Incentives

The psychology of rewards is a crucial component in any business. However, they should be seen as the proverbial double-edged sword: When utilized correctly, incentives can provide a major boost. But when they're mishandled, they can unleash chaos. They can make or break your business.

And if you happen to find yourself with a serious snake problem, you may want to avoid incentives altogether.

This post also appears on the branding psychology blog NeuroScienceOf

Matt Johnson, Ph.D., is a writer, speaker, and professor at Hult International Business School and Harvard University School of Continuing Education. He is the author of Branding That Means Business: How to Build Enduring Bonds between Brands, Consumers and Markets.

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Did a prisoner die from a needle prick when he was told that it was a snake bite?

I read somewhere that there was a prisoner facing a death sentence sometime before the 1950s, on whom a psychological experiment was conducted.

Experiment:

He was blindfolded and told that he would be killed by a bite by a venomous snake. But in reality, he was just pricked by a needle and he died from it. His autopsy report showed that he died from snake venom.

I did Google and I found this and this .

• Did something like that really happen?
• Is it really possible for a person to die from a placebo venom, like in the experiment?
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• I note that one of those sources claims that it was in the US. The other claims that it was Russian. Both are vague as to exact time and place. As fas as I can tell, neither one is notable. Do you have a source that is notable? –  Ben Barden Commented Jan 3, 2019 at 14:27
• @BenBarden Yes I've noticed that they claim to be from different countries. No, I do not found any notable source of the info. But AFAICT this seems to be pretty common story(?). –  noobs Commented Jan 3, 2019 at 14:31
• 5 Notability isn't related to whether the sources are reliable and accurate . It is whether it widely believed . The first reference admits they aren't sure whether it is true and the comments are mostly people believing it is false. –  Oddthinking ♦ Commented Jan 3, 2019 at 15:12
• 4 Note: The second story is posted by an author in India, is set in the USA, but is about a snake you'd find in India, not the USA. Let's find some more sources. –  Oddthinking ♦ Commented Jan 3, 2019 at 15:14
• Another claim example: ravislibrary.blogspot.com/2014/09/… –  Laurel Commented Jan 3, 2019 at 18:15

There is a set of very old urban legends - fictional stories that are widely believed and passed around as true - which are closely related to this story.

In the book The Lore of Scotland: A Guide to Scottish Legends (page 291), one variant is presented:

In 1824, an account appeared in print of Aberdeen students ganging up on an unpopular sacrist (a term used at Aberdeen University for a porter). The man, named as Downie, was subjected first to a mock trial in a black-draped room and then to an `execution'. The strokes of the axe were simulated by flicking his neck with a wet towel, so convincingly that the man died of shock, and the body had to be secretly buried.

Snopes points to a number of other more contemporary variants:

We’ve been hearing versions of this story for years, tales in which the details change but the theme remains that of an unfortunate man who dies after he is trapped in a situation which he presumes to be dangerous but is later revealed not to have posed any real threat to his well-being: The air-tight room he’s locked in turns out to have a vent to the outside which brings a steady supply of fresh air but the man suffocates because he believes he’s used up all the oxygen; the cooling unit on the refrigerated boxcar he’s trapped in isn’t turned on, but the man stuck inside the car slowly succumbs to hypothermia nonetheless. [...] Could someone really think himself to death? The jury may still be out on that concept, but we’ve yet to find any documentation for the claim that someone once died because his power of thought turned him into a corpsicle.

The executed prisoner story fits the format very well. Alas, this doesn't prove it never happened, but combined with the lack of traceable details (who, when and where?), and the inconsistencies between the stories, it seems fairly safe to dismiss these as modern folklore.

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Not the answer you're looking for browse other questions tagged medical-science history toxicology experiments placebo ..

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Video —Cobra Wave Explained

A long, interwoven lattice of popsicle sticks can release its stored energy in a visually impressive, propagating wave—a raised section of the structure akin to an angry cobra that spits out sticks as it moves. Researchers have now theoretically modeled this phenomenon and used high-speed video of these “cobra waves” to verify the model’s predictions for the wave’s shape and speed. They have also found that there is a narrow range of popsicle-stick lengths that can produce a cobra wave. The results may prove useful for understanding microtubules, which are biopolymers that rapidly unravel when their end cap is released.

Christophe Clanet of the École Polytechnique in Palaiseau, France, and Frédéric Chevy of the École Normale Supérieure in Paris each coached a team of physics students in a 2016 problem-solving competition, and together they decided that one of the problems— the one on cobra waves —deserved further study. In the first part of their new paper, Clanet, Chevy, and their colleagues reason that the wave motion is powered by the recoil resulting from ejecting sticks, and those sticks get their kinetic energy from the original potential energy stored when the sticks were bent to form the lattice. This thinking leads them to derive a wave speed formula that depends on the sticks’ material properties and on their length-to-thickness ratio but not on their width. The team verified these predictions in experiments with cobra waves made from six different types of sticks.

To explain the cobra-like shape, the researchers rely on elasticity theory, modeling the lattice as a uniform, continuous, and flexible material. They find that the shape depends on a competition between the recoil resulting from ejecting sticks—which keeps the raised section up—and the elastic and gravitational forces that pull it downward. They derive expressions for the cobra height in two regimes, depending on the relative importance of gravity (stick weight) compared with the sticks’ bending stiffness. While the light-stick regime seemed to break some of the assumptions of the model, the height predictions of the heavy-stick regime were accurate when compared with the team’s video data.

Finally, the team found that the cobra wave can only exist if each stick is short enough that the potential energy it stores when bent is larger than its gravitational energy when raised up. But each stick must also be long enough that it doesn’t break when creating the lattice.

This research is published in Physical Review Letters .

–David Ehrenstein

David Ehrenstein is a Senior Editor for Physics Magazine .

More Information

International Physicists’ Tournament problem that inspired this research

YouTube video of popsicle stick cobra wave

Popsicle-Stick Cobra Wave

Jean-Philippe Boucher, Christophe Clanet, David Quéré, and Frédéric Chevy

Phys. Rev. Lett. 119 , 084301 (2017)

Published August 25, 2017

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The COBRa study

The COBRa study, conducted as part of ESA´s SysNova technology assessment scheme, investigated an active debris removal concept relying on the exhaust plume of a monopropellant chemical propulsion system as a means to impart momentum and ultimately modify the orbit of a space debris object in a contactless manner.

The concept was scheduled to be demonstrated in-orbit making use of the Mango spacecraft from the PRISMA mission and the decommissioned CNES satellite Picard of the IRIDES mission. An interaction of such kind had never been studied before in any detail beyond chemical contamination effects.

Recently, the possibility of using satellites at the end of their life for In-Orbit Demonstration (IOD) of relevant debris removal concepts has been studied. Of particular interest is the ability of these spacecraft to perform close proximity operations combined with orbit and attitude modification between two co-flying satellites. The PRISMA mission, has successfully demonstrated high accuracy formation flying using the Mango and Tango satellites since its launch in 2010.

Following the nominal mission phase of PRISMA a further navigational experiment was to be performed. For this the still operational Mango satellite would rendezvous with the non-cooperative and de-commissioned Picard satellite, allowing a detailed analysis of the optimal rendez-vous phase. COBRa would then attempt the controlled alteration of the Picard attitude by use of plume impingement.

Specifically, the COBRa experiment was to be performed by pointing the thrusters of Mango towards Picard and conducting a small burn from a near-by spiral orbit. Optical observations by the visual camera on board Mango before and after the push would then enable on-ground evaluation of the change in the attitude dynamics of Picard.

Even though the IRIDES experiment and therefore also the COBRa In-Orbit demonstration could not be fully executed, due to a lack of propellant on Mango, it was possible to develop a technological framework for high-precision relative navigation control. In the context of evaluating the COBRa concept, mission analysis was conducted and essential vision-based navigation technology was consolidated. Generally, the experiment feasibility was demonstrated and critical areas were highlighted.

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Shielding studies for COBRA

A shielding is an essential part of any low background experiment. Its task is to minimise the amount of external particles and their secondaries reaching the detector. There are three types of particles a shielding is needed for: gamma rays, muons and neutrons. Most of the gamma rays originate from natural radioactivity, which leads to energies up to 3 MeV with the vast majority of the flux below the 2.6 MeV gamma ray peak of 208 Tl. Already 15 cm of lead or an equivalent passive shielding reduces the natural gamma ray flux sufficiently. Gamma rays induced by neutrons and cosmic muons can have much higher energies, but also have a considerable lower flux. The muons are usually of cosmic origin and thus can have very high energies. They are however highly ionising particles, which allows the use of a veto and of tracking methods to prevent them from generating background. As neutrons are more challenging to shield and potentially a very dangerous background source for the COBRA experiment, special emphasise is placed on them. (See the next section for more details on neutron shielding.) In addition the radioactive purity and the cosmic activation of the shielding materials have to be considered.

Neutron shielding

Simulated spectrum of the neutron induced energy deposition in a COBRA-detector made up of 64000 crystals for different shieldings with the same total thickness. The black full line indicates a pure lead shielding, the blue dotted line a standard multilayer shielding, the full blue line a composite like shielding and the dashed grey line an optimised multi layer shielding. The original energy spectrum of the incoming neutrons was calculated using a parametrisation for the muon induced neutronflux by [1] with values appropriate for the LNGS.

As neutrons do not carry an electrical charge, they are difficult to detect. They can however produce nuclear recoils, which could mimic the signal of low background experiments. Furthermore 113 Cd, which has a natural abundance of 12.22 %, has a very high cross section for the capture of thermal neutrons. This leads to additional background in the CdZnTe-crystals of the COBRA-experiment. In an underground environment like the LNGS there are two main neutron sources to consider. Neutrons from local radioactivity and neutrons induced by cosmic muons. Below 10 MeV the main contribution is due to spontaneous fission and (α,n)-processes due to interactions of α’s from natural emitters with light target nuclei in the rock. Neutrons with energies above 10 MeV are produced by nuclear reactions induced by cosmic ray muons. However, the flux of these neutrons is reduced considerably by beeing in an underground laboratory (see figure 1). At the LNGS neutrons from radioactive processes have a total flux which is about three orders of magnitude larger then the muon induced flux. However, due to their low energy they are easily shielded. Therefore, our main focus is on finding shieldings which are effective against the high energy muon induced neutrons. To study the shielding, Geant4 with the low energy expansion for dark matter experiments and MCNPX are used. An array of 64000 COBRA crystals with a total mass of about 400kg is simulated, surrounded by various shieldings. Types of shieldings considered are: shieldings consisting of a single material layer, multi layer shieldings, large water or liquid scintillator tanks and composite like shieldings with many thin layers of different materials. First results of this study are shown in figure 2.

COBRA Experiment

The Cadmium Zinc Telluride 0-Neutrino Double-Beta (COBRA) experiment is a large array of cadmium zinc telluride (CdZnTe) semiconductors searching for evidence of neutrinoless double beta decay and to measure its half life. COBRA is located underground, within the Gran Sasso National Laboratory. The experiment was proposed in 2001, and installation of a large prototype began in 2006.[1]

COBRA is designed to prove the validity of the CdZnTe detection technique.[2] The initial setup of the experiment, in 2007, was an array of four 1-cm3 CdZnTe semiconductors.[3] This was then upgraded to 64 detectors in a 4×4×4 array. The CdZnTe crystals act as both the detector and source material, as nine of the isotopes in this material are double beta decay candidates.[4] The location of the experiment allows for shielding from external gamma rays; to this end, the detectors are also shielded by 5 cm of radiopure electrolytic copper and 20 cm of low-radioactivity lead. 7 cm of boron-loaded polyethylene shields the experiment against neutrons, and the experiment is constantly flushed with nitrogen gas to prevent contamination with radon.[4] Results

As of 2016, COBRA had collected about 250 kg days of calibrated exposure.[2] Efforts were focused on reducing the background readings in order to increase the sensitivity of the experiment.[4] References

Wilson, J. R. (2008). "The COBRA experiment". Journal of Physics: Conference Series. 120 (5): 052048. doi:10.1088/1742-6596/120/5/052048. ISSN 1742-6596. Ebert, J.; et al. (2016-01-21). "The COBRA demonstrator at the LNGS underground laboratory". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 807: 114–120. arXiv :1507.08177. Bibcode:2016NIMPA.807..114E. doi:10.1016/j.nima.2015.10.079. ISSN 0168-9002. S2CID 110688200. Bloxham, T.; et al. (2007-08-03). "First results on double β-decay modes of Cd, Te, and Zn Isotopes". Physical Review C. 76 (2): 025501. arXiv :0707.2756. Bibcode:2007PhRvC..76b5501B. doi:10.1103/PhysRevC.76.025501. S2CID 119257817. Ebert, J.; et al. (2013). "Current Status and Future Perspectives of the COBRA Experiment". Advances in High Energy Physics. 2013: 1–6. doi:10.1155/2013/703572. ISSN 1687-7357.

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The COBRA IRIDES experiment

IAC-14,A6,6,9,x25456

Mr. Thomas Vincent Peters, GMV Aerospace & Defence SAU, Spain

Mr. Diego Escorial-Olmos, GMV Aerospace & Defence SAU, Spain

Mr. Andrea Pellacani, GMV Aerospace & Defence SAU, Spain

Mr. Marcos Avilés Rodrigálvarez, GMV Aerospace & Defence SAU, Spain

Prof. Michèle Lavagna, Politecnico di Milano, Italy

Mr. Fabio Ferrari, Politecnico di Milano, Italy

Mr. Primo Attina, Italy

Mr. Guido Parissenti, Thales Alenia Space Italia, Italy

Mr. Alexander Cropp, ESA, The Netherlands

IAC-14,A6,6,9,x25456.brief.pdf

IAC-14,A6,6,9,x25456.pdf (🔒 authorized access only).

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The Cobra-IRIDES Experiment

Alexander Cropp ESA, the Netherlands, [email protected] The COBRA IRIDES is a proposed experiment to modify the attitude motion of a non-cooperative satellite by means of the interaction between the thruster exhaust gases and the target satellite. Previously the COBRA concept was studied as an active debris removal system which relies on contactless technology to modify the state of a space debris object. Currently a proof-of-concept demonstration is proposed in the form of an experiment to be performed with the Mango and the Picard satellites. The COBRA concept was proposed as a solution to one of the challenges issued by ESA within the framework of the SysNova competition, and subsequently won this competition. The original goal of COBRA was to modify the motion of a space debris object by means of chemical propulsion plume impingement. Two effects were studied, namely the modification of the orbital parameters of the target object for the purpose of deorbiting it and modification of the attitude of the target for the purpose of control. The efficiency of the first effect is debatable in the frame of active debris removal missions, but the second effect was found to be extremely useful in this frame. Active debris removal missions will benefit from contactless methods to perform de-tumbling or attitude rate reduction of the target object before attempting the capture itself. The COBRA IRIDES experiment is to be performed after the completion of the IRIDES experiment, the goal of which is to perform close rendezvous with a non-cooperative satellite (Picard). After the IRIDES experiment ends, Mango will be in close proximity of Picard. The objective of the COBRA experiment is to use plume impingement of Mango's thrusters on the surface of Picard to induce torque on the Picard satellite and impart a new rotational state. The rotational state before and after the thruster firing will be determined by means of observations with Mango's on-board camera. The study will address, amongst others, the relative trajectories to be used, the thrusting strategy, the expected effect of the plume on the motion of Picard, the operational aspects of the experiments, including ground interaction and ground contacts, and the image processing and navigation required to perform the experiment and determine the effect of the plume impingement. The paper will present the results of the study and the current status of the COBRA IRIDES experiment.

Related Papers

Thomas Peters

COBRA is a contactless concept for de-tumbling and controlling the attitude of a target space debris object that exploits the torques generated on the target by the plume impingement of a thruster facing the target. The control strategy for de-tumbling is based on a switching strategy for the de-tumbling thruster and a pointing strategy for aiming the de-tumbling thruster at a specific region of the target. This control strategy has been developed in a previous internal study of the concept. This article discusses further developments of the original strategy and examines the general applicability of the COBRA concept, mainly in Active Debris removal missions in line with Cleanspace. The applicability of COBRA concept is investigated by examining several scenarios, namely, de-tumbling and attitude control of debris objects of varying configurations in terms of object geometry and mass parameters and in various initial rotation states. The main targets examined in this study are Envi...

Fabio Ferrari , Thomas Peters

This paper presents the preliminary analysis of an in-orbit demonstration opportunity to test plume impingement as a viable means to change the attitude state of a space debris based on the Prisma and Picard missions. This technique has been proposed as part of the COBRA concept studied by ESA in collaboration with GMV, Politecnico di Milano and Thales-Alenia Space, as an active debris removal concept relying on the exhaust plume of a monopropellant chemical propulsion system as a means to impart momentum and ultimately modify the orbit of a space debris object in a contactless manner. The feasibility of the experiment is presented as well as its critical areas, no showstoppers are identified.

Fabio Ferrari

Journal of Space Safety Engineering

Thomas Terzibaschian

Active Debris Removal (ADR) is one of the current hot spots in space research. Plenty of engineering challenges, it deals with uncooperative and tumbling orbiting objects to be approached and captured autonomously by another space vehicle, to eventually change their dynamics either directly transferring them to a disposal orbit or providing a control device to be attached to the dead element to make it controlled up to disposal. Different techniques are being proposed in literature, starting from the classical robotic arm to grasp the target up to action-reaction principle exploitation with no contact at all, such as gas plume impinging on the object surfaces to change its momentum. In particular, the use of proximity blow effects of a chemical thruster can be exploited to intervene on the uncooperative object angular momentum to control its rotational dynamics and prepare it for capture. Chemical propulsion is a high TRL technology that would not require long development and validation plan for the proposed application. A key point for this technology to be effective stays in evaluating the actual energy transfer between the gas particles and the uncooperative object, and its sensitivity to the several parameters the scenario depends on. This paper discusses the numerical simulator implemented at Politecnico di Milano to assess the feasibility and performance of this attitude control strategy, and its sensitivity to the numerous parameters involved in its design, looking for criticalities, benefits and drivers. The physical mechanism of momentum transfer, at the base of the simulator, is described at first: the investigation of the momentum transfer mechanism requires the definition of a plume model and a plume impingement model to simulate the interaction with the debris surface. The effects of the impinging plume on the angular dynamics of the debris object are then presented. An application of the method to a study case is presented to show the effectiveness and the applicability of this method. The effects of the system physical characteristic on the dynamics are also discussed. It is demonstrated, through the above-mentioned simulator, how the concept of de-tumbling targets using gas plume impingement may be very attractive in future ADR missions: attitude control strategies can be found to fulfil the requirements of de-tumbling space debris with chemical engine to safer face the subsequent disposal phase.

Advances in Space Research

Norman Fitz-coy

The Aeronautical Journal

A. Mafficini

ABSTRACTThe RemoveDEBRIS mission has been the first mission to successfully demonstrate, in-orbit, a series of technologies that can be used for the active removal of space debris. The mission started late in 2014 and was sponsored by a grant from the EC that saw a consortium led by the Surrey Space Centre to develop the mission, from concept to in-orbit demonstrations, that terminated in March 2019. Technologies for the capture of large space debris, like a net and a harpoon, have been successfully tested together with hardware and software to retrieve data on non-cooperative target debris kinematics from observations carried out with on board cameras. The final demonstration consisted of the deployment of a drag-sail to increase the drag of the satellite to accelerate its demise.

Danil Ivanov

Relative motion control problem for capturing the tumbling space debris object is considered. Onboard thrusters and reaction wheels are used as actuators. The nonlinear coupled relative translational and rotational equations of motion are derived. The SDRE-based control algorithm is applied to the problem. It is taken into account that the thrust vector has misalignment with satellite center of mass, and reaction wheels saturation affects the ability of the satellite to perform the docking maneuver to space debris. The acceptable range of a set of control system parameters for successful rendezvous and docking is studied using numerical simulations taking into account thruster discreteness, actuators constrains, and attitude motion of the tumbling space debris.

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Systems Thinking and the Cobra Effect

A famous anecdote describes a scheme the British Colonial Government implemented in India in an attempt to control the population of venomous cobras that were plaguing the citizens of Delhi that offered a bounty to be paid for every dead cobra brought to the administration officials. The policy initially appeared successful, intrepid snake catchers claiming their bounties and fewer cobras being seen in the city. Yet, instead of tapering off over time, there was a steady increase in the number of dead cobras being presented for bounty payment each month. Nobody knew why.

Right from birth, we start to see connections in the world around us. A meal cures hunger; sleep relieves tiredness; problems have causes, and eliminating the cause will yield a solution. What we are doing (whether we know it or not) is forming mental models of the way that cause and effect are related. Our mental models exert an incredibly powerful influence on our perceptions and thoughts. They determine what we see, tell us what events are important, help us to make sense of our experiences, and provide convenient cognitive shortcuts to speed our thinking.

However, they can lead us astray. Most of our cause–effect experiences involve very simple, direct relationships. As a result, we tend to think in terms of ‘linear’ behaviour — double the cause to double the effect, halve the cause to halve the effect. In reality, as we will see with the cobras of Delhi, the world is often more complex than we realise.

Counter-intuitive behaviour

We live in a highly connected world where management actions have multiple outcomes. When action is taken, the intended outcome might occur, but a number of unexpected outcomes will always occur . While an unexpected outcome can be beneficial, such serendipitous events are extremely rare. What is more likely is that the unexpected outcomes will be unwanted — these outcomes can be thought of as counter-intuitive ‘policy surprises’ . If we want to avoid unwanted policy surprise, then we need to improve our intuitions concerning the operation of cause and effect in complex social-ecological systems.

Developing methods to help us visualise and understand cause-and-effect relations in complex systems is of great importance. We need ways to progress beyond linear thinking . In particular, we need to understand the concept of feedback and appreciate the dominant role it plays in determining system responses to management initiatives .

Reinforcing and balancing feedback

There are just two forms of basic feedback loop: reinforcing and balancing. Figure 1 provides an example of ‘reinforcing feedback’ (also called ‘positive feedback’). This diagram expresses the hypothesis that an increase in the availability of active-transport opportunities will increase the extent to which community members ‘see’ the benefits of active transport. An increase in the visibility of benefits leads to increased community commitment to active transport, which leads to a further increase in the availability of opportunities for active transport. Similarly, if the level of any of the variables in this reinforcing loop is decreased, this change will propagate around the loop to decrease that level further. This amplifying effect, which can drive accelerating growth or collapse of the active transport system, can be triggered by an increase or decrease in any of the variables in the loop.

Figure 1. A Reinforcing Feedback Loop. In this influence diagram the blocks of text represent system variables and the arrows represent the processes or mechanisms by which a change in the level of one variable affects the level of another variable. A plus sign on an arrow indicates that a change in the variable at the tail of the arrow will cause the variable at the head of the arrow to eventually change in the same direction. The upper-case R in the centre of the diagram indicates that this is a reinforcing loop which generates feedback forces that act to amplify change.

The other basic cause-effect loop is ‘balancing feedback’. Balancing feedback (also called ‘negative feedback’) is ‘goal seeking’. It is the basis for artificial and natural control systems and system resilience. Figure 2 shows a case where the goal is to maintain a sustainable level of resource consumption — high enough to meet the community’s needs, but low enough to ensure the long-term viability of the resource. If, for example, the actual level of resource consumption rises above the sustainable level, then action is taken to reverse the change. The feedback loop works to minimise the difference between the two levels — ideally the difference will be maintained close to zero.

Figure 2. A Balancing Feedback Loop (B), which generates feedback forces that act to oppose change. A minus sign on an arrow indicates that a change in the variable at the tail of the arrow will cause the variable at the head of the arrow to eventually change in the opposite direction. The signs shown in this diagram are appropriate for the case where actual consumption exceeds the sustainable level.

In a complex, real-world system there will be multiple reinforcing and balancing feedback loops, interacting with each other. Despite this, most of us still think in terms of simple causal chains, and immediate, linear effects. In particular, we tend to overlook feedback between decisions that are made by management groups that are operating in isolation from one another. This cross-sector feedback is largely invisible because there is little communication between the managers in the different ‘silos’. To make matters worse, major feedback effects are often delayed (sometimes by decades or longer!), or occur at locations distant from the triggering actions making them hard to detect or attribute.

A decision maker who seeks to anticipate the way that a complex system will respond to a planned management initiative faces a ‘complexity dilemma’. The behaviour of a complex system emerges from the feedback interactions between its parts. This means that, on the one hand, its behaviour cannot be understood from a study of the parts taken one by one in isolation — the system needs to be looked at as a whole. On the other hand, such systems turn out to be far too complex to be studied as a whole. When faced with this dilemma, time-poor decision makers tend to do one of two things. Either they study a small part of the system in isolation, thus ruling out their chances of seeing significant cross-sector feedback effects, or they simply abandon their attempt to be systemic. Either way they fail to avoid future policy surprise.

But there is a third possibility. Managers sometimes seek to develop working dynamical models that can help them to anticipate possible unwanted outcomes of proposed actions. The idea that one can have a model to run in advance of reality is very attractive. Nevertheless, the construction of useful detailed models is a difficult undertaking that requires significant amounts of reliable time-series data and the participation of expert data analysts and modellers. In many situations these conditions cannot be met.

Simple dynamical models

There is, however, a type of modelling that can improve decision making in almost all situations. Efforts to build extensive working models of complex business systems have led to the discovery of simple feedback structures that occur over and over again in many different contexts. These ‘system archetypes’ have characteristic behaviours that can provide feedback-based explanations of behavioural patterns that are commonly observed in human–environment systems and are relevant in real-world policy-making and management contexts.

Take, for example, a Fixes that Fail feedback structure (Figure 3). This archetype captures the common tendency of decision makers, when faced with a problem, to apply a ‘fix’ that reduces the strength of the problem. While it seems to work in the first instance, the fix fails in the long run because it has an unexpected outcome that amplifies the problem.

Figure 3. Freeway Feedback. This influence diagram shows a specific example of the generic Fixes That Fail system archetype. The short parallel lines drawn across two of the arrows represent delayed effects.

The dynamical story told in Figure 3 concerns the development of freeways as a means to reduce traffic congestion. As existing roads become congested, so too commuting times increase. Commuting times in excess of the desired time frustrate the community and eventually lead to corrective action — the ‘fix’. In this case, the fix involves constructing new freeways. As soon as a new freeway is opened to traffic there is an immediate reduction in commuting times, and everyone is happy. Then, with a delay, the existence of the freeway (with its short commuting times) encourages people to move out to the peri-urban areas at the end of the freeway. So, the new freeway triggers urban sprawl. More people, more cars, and more congestion. Once again commuting times become a problem, even on the freeway. What to do? Well, last time we had this problem we built a new freeway…

System archetypes are, of course, not models of complex systems, and must therefore be used with an understanding of their limitations. Their discovery does, however, suggest that simple dynamical models have the potential to improve policymaking and management decisions in complex situations. Experience with such models can alert decision makers at all levels to the potential for feedback forces to cause policy surprise. For example, it would be a significant step forward if all decision makers recognised the potential for balancing feedback structures to cause the well-known phenomenon of ‘policy resistance’, where people push on a system and the system pushes right back to resist their efforts. This, after all, is the essence of resilience.

Given the increasing complexity of human–environment systems in the 21st century, the need for practical ways to promote and use feedback thinking has never been greater.

Simple dynamical models must be used with caution. They can never tell the whole story. Their main value lies in their potential to make concrete the message that we must take into account feedback effects in the policy-design processes for complex systems. It is not necessary for all policymakers to become competent system modellers, but it is necessary for them to understand that feedback effects must be considered. Given the increasing complexity of human–environment systems in the 21st century, the need for practical ways to promote and use feedback thinking has never been greater.

UNU is using this approach to help stakeholders map out opportunities and barriers to in the field of urban health, which is especially amenable to such techniques given the multi-faceted and interconnected nature of health outcomes in cities. By having different stakeholders create their own diagrams, they can be merged and simplified allowing everyone to see how their own understanding of the system relates to everyone else’s, thus strengthening communication and broadening their outlook. They also serve as an educational tool by which people with very different academic trainings and understandings of a problem can come together speaking a common language.

With this understanding in mind, policymakers can at least be aware of potential unintended consequences along the way and maybe some areas where synergies can be found. The systems analysis approach is also explicitly identified as the key methodology for a new ICSU 10-year research program on Health and Well-being in the Changing Urban Environment co-sponsored by UNU and the Interacademy Medical Panel (IAMP) hosted by the Chinese Academy of Sciences in Xiamen.

The cobra effect

By now, you may have figured out what happened in the Delhi anecdote with which we opened. Realising that the cobra bounty converted the snakes into valuable commodities, entrepreneurial citizens started actively breeding them (a similar and well-documented event happened with the French who tried to eradicate rats from Hanoi).

Under the new policy, cobras provided a rather stable source of income. In addition, it was much easier to kill captive cobras than to hunt them in the city. So the snake catchers increasingly abandoned their search for wild cobras, and concentrated on their breeding programs. In time, the government became puzzled by the discrepancy between the number of cobras seen around the city and the number of dead cobras being redeemed for bounty payments. They discovered the clandestine breeding sites, and so abandoned the bounty policy. As a final act the breeders, now stuck with nests of worthless cobras, simply released them into the city, making the problem even worse than before!

The lesson is that simplistic policies can come back to bite you. The next time you hear a politician proclaiming a simple fix to a complex problem, check for the feedback cobras lurking in the bushes!

Barry Newell

Dr. Barry Newell is a Visiting Research Fellow at the United Nations University International Institute for Global Health in Kuala Lumpur, Malaysia, and an Honorary Associate Professor (Research School of Engineering) and a Visiting Fellow (Fenner School of Environment & Society) at the Australian National University. He has also held research and teaching positions at Yale University and Kitt Peak National Observatory (Arizona). A physicist who focuses on the dynamics of social-ecological systems, he has particular interest in the critical importance of shared language in trans-disciplinary investigations of system behaviour. His work involves developing practical ways for groups to use systems thinking and focused dialogue to improve their decisions and policy making. Developing Collaborative Conceptual Modelling (CCM), a high-level approach which provides conceptual guidance for trans-disciplinary research and cross-sector management, is one aspect of this work.

Christopher Doll

Christopher Doll is a Research Fellow at United Nations University Institute of Advanced Studies. His research interest focuses on using spatially explicit datasets to support policymaking for sustainable development with application in areas of urbanisation and biodiversity. He has previously held positions at Columbia University in New York and the International Institute for Applied Systems Analysis in Austria. Born and educated in the UK, Christopher holds a PhD in Remote Sensing from University College London.

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