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Chapter 9

CHAPTER 9 NOTES - Evolutionary Pscyh

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PSYC 3420
Irwin Silverman

CHAPTER 9: COOPERATIVE ALLIANCES THE EVOLUTION OF COOPERATION • Natural selection is competitive • It is selfish because it is a feedback process in which one organism's design features out reproduce those of others in an existing population • Sacrifices are costly to those who make them, yet they benefit the people for whom the sacrifices are made THE PROBLEM OF ALTRUISM • Problem of altruism: how could altruism among nonrelatives possibly evolve, given the selfish designs that tend to be produced by natural selection • An "altruistic" design feature aids the reproduction of other individuals, even though it causes the altruist suffer a fitness cost • Evidences that suggest a long history of altruism: 1. Evidence that social exchange - a form of cooperation - occurs across human cultures and is found frequently in hunter-gatherer cultures that are presumed to closely resemble the ancestral conditions under which humans evolved 2. Other species that are far removed from humans, such as vampire bats, also engage in forms of social exchange 3. Other primates besides humans, such as chimpanzees, baboons, macaques, also engage in reciprocal helping A THEORY OF RECIPRICALALTRUISM • Solution to the problem of altruism has been developed by the theory of reciprocal altruism - cooperation between two or more individuals for mutual benefit - adaptations for providing benefits to nonrelatives can evolve as long as the delivery of such benefits is reciprocated at some point in the future • Gain in trade - what economists call when each party receives more in return than it costs to deliver the benefit • Those engaged in reciprocal altruism will out reproduce those who act selfishly, causing psychological mechanisms for reciprocal altruism to spread in succeeding generations • The problem of cheating: when someone could pretend to be a reciprocal altruist, but then take benefits without responding in kind later TIT FOR TAT • The game "Prisoner's Dilemma" - is a hypothetical situation in which two people have been thrown in prison for a crime they are accused of committing together and of which they are guilty • Prisoners are held in two separate rooms, and the police tries to interrogate both prisoners to rat one another out • If neither rats, the police will have to set them both free for lack of evidence • If both confess, they will both be sentenced to jail EVOLUTION CHAPTER 9 page 1 • If one confesses and implicates his partner, he will be given a reward and implicated partner will be sentenced to jail o R= reward for mutual cooperation (neither prisoner tells) o P= punishment each prisoners receives if both confess o T= temptation to defect (reward given in exchange for implicating the other) o S= sucker's payoff (penalty one incurs if his partner defects and he doesn't) • The rational course of action for both prisoners is to confess, but that would have a worse outcome for both than if they decided to trust each other (the dilemma) • The logical course of action, no matter what one's partner does, is to defect, even though cooperation would result in the best outcome for both • This dilemma resembles the problem of reciprocal altruism • Is the game is played once, then the only sensible solution is to defect • Axelrod and Hamilton showed that the key to cooperation occurs when the game is repeated a number of times but each player doesn’t know when the game will end, as often happens in real life • The winning strategy in "iterated prisoner's dilemma" game is called tit for tat • Axelrod and Hamilton discovered this strategy by conducting a computer tournament • The strategies consisted of decision rules for interacting with other players • There were two rules: 1. cooperate on the first move 2. Reciprocate on every move thereafter • Start by cooperating, and continue cooperating if the other is also cooperating • If the other defects, then defect is kind - Trivers labeled this "contingent reciprocity" • Axelrod identified three features of this strategy that represented the keys to its success: 1. Never be the first to defect 2. Retaliate only after the other has defected 3. Be forgiving COOPERATION AMONG NONHUMANS • Each species is unique in many of the adaptive problems it has confronted over the course of its evolution, but different species can arrive at similar solutions to common adaptive problems • It is instructive to examine nonhuman species to see whether they have evolved cooperation STRATEGIES FOR PROMOTING COOPERATION [BOX 9.1] • According to Axelrod's analysis of tit for tat as a key successful strategy, several practical consequences follow for the promotion of cooperation 1. Enlarge the shadow of the future - if the other individual thinks that you will interact frequently in the extended future, he/she has a greater incentive to cooperate 2. Teach reciprocity - promoting reciprocity not only helps oneself by making others more cooperative, it also makes more difficult for exploitive strategies 3. Insist on no more than equity - greed is the downfall of many; promoting equity tit for tat elicits cooperation from others EVOLUTION CHAPTER 9 page 2 4. Respond quickly to provocation - if your partner defects on you, a good strategy is to retaliate immediately 5. Cultivate a personal reputation as a reciprocator - we live in a social world in which the beliefs other have about us (our reputations) determine whether they will befriend or avoid us FOOD SHARING IN VAMPIRE BATS • Vampire bats' survival depends on other animal's blood • The bats' ability to feed successfully increases with age and experience • One study found that 33% of the younger bats failed to get blood on any particular evening, whereas only 7% of the bats older than two years failed to feed • Failure at feeding, in fact, can quickly lead to death • Bats can go 3 days without feeding • Failure is common; all bats fail at one point or another, so the risk of death due to starvation is a constant threat • Wilkinson discovered that the bats regularly regurgitate a portion of the blood they have sucked and give it to others in the bat colony, but not randomly • Only bats that were sighted in close proximity at least 60% of the time received blood from that compatriot; not a single bat gave blood to another bat with whom he associated for a lesser period of time • In another study, Wilkinson used a captive colony of vampire bats to explore additional aspects of reciprocal altruism • He deprived individual bats of food, and varied the length of the deprivation • The "friends" tended to regurgitate blood more often when their friends were in dire need and close to starvation than when they were in mild need • The starved bats who received help from their friends were more likely to give blood to those who had helped them in their time of need • Vampire bats show all signs of having evolved reciprocal altruism CHIMPANZEE POLITICS • A chimp named Yeroen at a zoo in the Netherlands, reigned as the dominant adult male • His dominance extended to sexual activity • Although there were four adult males in the troop, he was responsible for nearly 75% of the matings when the females came to estrus • As he grew older, things began to change • A younger male, Luit, experienced a sudden growth spurt and challenged Yereon's status • Reciprocal alliances with females are essential to the maintenance of status - males defend the females against attack from other males and act as "peacemakers" in disputes; in return, the females support the males, aiding in the maintenance of their status • The females gradually began to defect and sided with Luit as Luit's increasing dominance became apparent • After 2 months, Yereon had be dethroned and started to display the submissive greeting to Luit • Luit achieved 25% of the matings during Yereon's reign of power, his copulations jumped to more than 50% when he took over • Yeroen's sexual access dropped to zero EVOLUTION CHAPTER 9 page 3 • Although outsed from power and sexual access, Yereon was not ready to retire • Gradually, he formed a close alliance with an upcoming male named Nikkie • Neither of the two dared to challenge Luit alone, but together they made a formidable alliance • A physical fight erupted between them, and Nikkie and Yereon triumphed • After this victory, Nikkie secured 50% of matings, and Yereon now secured 25% of the matings (from his development of 0) • Alliances are central features in the social lives of chimpanzees • Without alliances with the females, males could never attain a position of dominance in the troop • The key strategy in formation of chimpanzee alliances: try to sever the alliances of one's opponents and enlist the former allies COOPERATION AND ALTRUISM AMONG HUMANS SOCIAL CONTACT THEORY • The theory of reciprocal altruism predicts that organisms can benefit by engaging in cooperative exchange • There is one problem: many potential exchanges do not occur simultaneously • In nature, opportunities for simultaneous exchange occur • But in many contexts, there are opportunities for cooperation in which simultaneous exchange is simply not possible • Another reason that simultaneous exchange is sometimes not possible is that the needs and abilities of the interactants are rarely perfectly matched • Whenever the exchanges are non-simultaneous, the window is open for defection - taking the benefit and later cheating and failing to return the favour • Cosmides and Tooby have developed social contract theory to explain the evolution of cooperative exchange in humans, with special attention to how humans have solved the problem of cheating • The possibility of cheating poses and ever-present threat to the evolution of cooperation • The reason is that cheaters have an evolutionary advantage over cooperators, at least under certain conditions • Over evolutionary time, cheaters will thrive more than cooperators until the entire population consists of noncooperators • Reciprocal altruism can only evolve if the organisms have a mechanism for detecting and avoiding cheaters • Cosmide and Tooby outlined five cognitive capacities: 1. The ability to recognize many different individual humans • One study showed that people can identify others whom they have not seen for up to 30-40 years, which is a recognition of over 90% • There is a neurological evidence that this ability is located in a specific area of the brain • People with a lesion in a specific area in the right hemisphere develop a highly specific deficit: an inability to recognize faces, called prosopagnosia EVOLUTION CHAPTER 9 page 4 • Humans are also specially good at recognizing other individuals solely by the way they walk 2. The ability to remember the histories of interaction with different individuals • This capacity breaks down into several different abilities:  One must be able to remember whether the person with whom one has interacted was previously a cooperator or a cheater  One must be able to keep track of who owes what to whom 3. The ability to communicate one's values to others • If you fail to communicate your distress to a defector, you might be vulnerable to future defections • Ex. Consider DeWaal's chimpanzees study:  Although chimp communications are nonverbal, among humans, language can be used to supplement emotional expressions and other nonverbal behaviour as the medium of communication of desires, entitlements, and distress about an unfulfilled obligation 4. The ability to model the values for others • If you detect when a person is needy and how he/she is needy, the benefit you provide can be tailored to that need • By understanding the desires and needs of others, you can tailor you exchanges to maximize the benefit you provide, making the other person more indebted to you than if you had failed to model his/her values 5. The ability to represent the costs and benefits, independent of the particular items exchanged • Cosmides and Tooby argue that many animals exchange a delimited set of items, such as food and sex • Evolved mechanisms of social exchange cannot be prewired to represent (conceptualize) and negotiate for specific items • It is our general ability to represent the costs and benefits of a exchanges, not a specific ability tied to particular items, that has evolved in humans • Social contract theory proposes that the evolution in humans of five cognitive capacities to solve the problem of cheaters and engage in successful social exchange EVIDENCE FOR CHEATER-DETECTION ADAPTATIONS • To test social contract theory, Cosmides and Tooby conducted more than a dozen empirical studies on people's responses • Logic refers to the interferences one can make about the truth of one statement from the truth of other statements, independent of their form • If P then Q, then if P is true, Q must also be true • Humans do not seem to be very good at solving logical problems • Consider one type of logic problem • Imagine that four cards are lying on a table • Each card has a letter on the one side and a number on the other, but you can see only one side • Now consider: which cards would you need to turn over to test the following rule "if a card has a vowel on one side, then it has an even number on the other side" • People are really bad at solving problems of this sort EVOLUTION CHAPTER 9 page 5 • According to Cosmides and Tooby, the answer is that humans have not evolved to respond to abstract logical problems: they have, however, evolved to respond to problems structured as a social exchanges when they are presented in terms of costs and benefits • People reason correctly when the problem is structured as a social contract • People do well when they are "looking for cheaters", those who have taken a benefit without paying the cost • For people to succeed at this task, it need only be structured such that they will construe the problem in terms of taking benefits and paying costs • Cosmides and Tooby were able to rule out a number of alternative hypotheses: o The effect does not depend on being familiar with the content of the problem • When strange or unfamiliar rules were used, roughly 75% of subjects answered correctly; 10% of subjects got it right in the abstract version • The human mind has an evolved psychological mechanism specifically designed to detect cheaters • There's a cross cultural evidence that points to the universality of a cheater-detection adaptation in social exchange o Work conducted with brain-damaged patients by Valerie Stone, provides additional evidence for a specific cheater-detection adaptation • One patient R.M. had sustained damage to his orbitofrontal cortex, and amygdala, two regions of the brain • R.M. Was able to reason correctly on some problems such as problems structured as "precaution rules" • And he did poorly on social contract problems • The dissociation between R.M's performance on the two types of reasoning tasks suggests that social-exchange reasoning might be a separate and specialized component of the human cognitive machinery • People with R.M's pattern of brain damage are susceptible to scams, exploitive relationships, and unfavourable business deals o The cheater-detection mechanism appears to be highly sensitive to the perspective one adopts • Perspective appears to govern the sorts of cheaters one looks for DO PEOPLE REMEMBER CHEATERS? • Memory may play a special role in cheater detection • One study found that people remember the faces of known cheaters, specially low- status cheaters, better than they remember the faces of known cooperators • Memory in cheaters may partly depend on their rarity in population • One study found that cheaters were remembered best when they were rare but worse when they were quiet common • Other studies, show that people have better "source memory" for the faces of cheaters - that is good memory for the specific cheating context in which the faces were encountered • Another study found that people remember the faces of real cheaters better than those of real cooperators, even when they have no knowledge that these individuals have actually cheated or cooperated • Oda and Nakajima discovered that people show excellent face recognition for nonaltruists in one experimental game, and behaviourally avoid interacting with them in subsequent experimental games EVOLUTION CHAPTER 9 page 6 • Another study found that people show an automatic attentional bias toward the faces of people who had previously not cooperated during prisoner's dilemma game • These results support the hypothesized cognitive capacities, both in attention and memory, in cheater detection • people appear to have evolved psychological mechanisms designed to attend to, remember and detect cheaters - mechanisms that are activated whenever exchanges are structured in terms of costs and benefits THE DETECTION OF PROSPECTIVE ALTRUISTS • Once a cheater-detection adaptations has evolved in humans, selection will favor coevolved adaptations to avoid being detected as cheaters • Cheater-detection adaptations lead to increasingly subtle forms of cheating • According to William Michael Brown, humans have evolved another adaptation to solve this problem: the ability to detect the genuineness of altruistic acts • Brown and Moore created a version of the Wason selection task to test whether people look for the existence of genuine emotions that might lie behind an act of altruism • The task had the following rule: "if X helps, then X seeks credit" • Participants in the study then indicated which cards they would turn over • The logic behind this task is that people who help others only to receive some form of external credit for doing so are not good candidates for helping in the future and so make poor cooperative allies • Those who help others without seeking external credit, display genuine altruistic tendencies and so would make excellent allies • The correct answer from the perspective of altruistic detection, would be to select the cards "X helps" and "X does not seek credit" • Brown and Moore found through two different experiments that the majority of people choose the pattern of cards that allowed them to detect altruists • The performance on the altruists=detection tasks was nearly as good as performance on cheater-detection tasks, and both were better than performance on the abstract problems • Research found that success of performance on altruistic-detection task was not linked with success of performance on the cheater-detection task, indicating the two abilities are distinct • In one study, judges watched 20 sec silent video clips of strangers and then asked to estimate the person's generosity on
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