Reciprocal Altruism and Group Behavior By Alejandra Fernandez-Ortega

Reciprocal Altruism Beneficial acts to non-relatives that are later repaid by the beneficiary Prerequisites: Cost of the altruistic act must be lower than the benefit to the actor Animals must be capable of recognizing each other in order to reciprocate and detect cheats Must have reasonably long lifespan in order to re-encounter individuals and to have the chance for reciprocation to occur Unlike kin selection, rare in animal kingdom

Examples of Reciprocal Altruism in Animal Kingdom Olive baboons Vampire bats Green woos hoopoe Dolphins Vervet monkey

Examples of Reciprocity in Pre-Industrial Societies Yanomamo of South America Small, permanent villages and slash-burn agriculture Division of labor, economic specialization and trade economy Reciprocity more limited, wealth accumulated and not equally divided !Kung San of South Africa Small, nomadic bands of hunter-gatherers Gift economy-all meat shared equally across tribe, with expected reciprocity Hoarding meat or boasting about hunting skill is cultural taboo Makes evolutionary sense within nomadic hunter gather society Extremely high murder rate

Game Theory and the Prisoner’s Dilemma Game Theory: finding the best possible solution to a problem taking into account what everyone else does Prisoner’s dilemma: the optimal outcome for a group is achieved only when each individual cooperates, or makes a decision that would not be in his individual best interests R=mutual reward for cooperation, T=temptation to defect, P=Punishment for mutual defection, S=sucker’s payoff T>R>P>S

Iterated Prisoner’s Dilemma and Reciprocal Altruism In a single occurring prisoners dilemma, logical choice is to defect However, in re-occurring social situations, people fall into patterns of mutual cooperation because they each know that if they cooperate they can expect future cooperation in the form of reciprocity and if they defect, they can expect retaliation in the future Tit-for-tat Nice Retaliatory Forgiving

Indirect Reciprocation Critique of reciprocal altruism theory-people commit acts of altruism that cannot hope to be repaid directly by the beneficiary E.g. blood drive Indirect reciprocation-demonstrating cooperation and selflessness makes others more likely to cooperate in the future Reputation and social worth Karma?

Study of Individual Differences in Reciprocity Styles (Houser & Kurzban, 2004) Subjects randomly assigned to a series of 4-person groups for at least 7 games Could invest tokens into private accounts or pool into a public account to be doubled and shared (Prisoner’s Dilemma) Each participant in turn given at least one chance to change allocation based on current total contribution to public account

Results Cooperation strategies proved stable across games Cooperators (13%)-contributed a great deal most of the time, regardless of overall group contribution (~50 tokens) Free riders (20%)-contributed almost nothing most of the time, regardless of overall group contribution (~1 token) Reciprocators (63%)-based their contributions on how much others in each game contributed (~25 tokens)- No statistical difference in individual earnings between types Group composition predicted future cooperation levels

Implications In any given population there are stable, distinct, and co-existing cooperative strategies that predict reciprocal altruism Cooperators-contribute to group welfare at cost to self Free riders-do not contribute, no cost to self Reciprocators-conditional strategy High levels of free riders reciprocators in a population predict a break down in group cooperation and reciprocity.

Personality Traits and Social Cognitive Beliefs Predicting Altruistic Styles (Alessandri et. al., 2009) Study: 377 adolescents Completed measurement scales measuring trait agreeableness, social cognitive self evaluations and prosociality at ages 16 and 18 Findings and implications: Agreeableness personality trait and empathic self efficacy beliefs were correlated with degree of cooperation and self sacrificing altruistic behaviors. High degree of heritability for agreeableness implies that individual differences in altruistic behavior are largely heritable Changes in agreeableness and empathic self efficacy across time predicted similar changes in altruistic and other prosocial behaviors In general, females score higher on agreeableness, empathic self efficacy, and altruistic prosocial behaviors compared to males Agreeableness as a broad personality trait may have evolved as a general mechanism for direct and indirect social reciprocity

Social Cognition and the Development of Reciprocal Altruism (Barret & Tooby, 2010) While many animals have kin selection, very few species have reciprocal altruism Hypothesis: for reciprocal altruism to be effective, must have theory of mind necessary to predict the intents of others, to maximize reciprocal gain and minimize free riding losses Humans have evolved special cheater detection mechanisms to predict the intents of humans which help us make decisions about whether or not to reciprocate

Study: “Ability” condition “Intent” condition “Benefit” condition Hypothesis: people should be able to predict whether or not someone has an incentive to “cheat” or free ride based on whether or not they would benefit Finding: Research subjects increased their vigilance for cheating by 20% when they believed that the person’s kin would gain by free loading behavior “Ability” condition Hypothesis: people should be more wary of potential cheating and dishonesty if they believe that the other person has the opportunity to free ride Finding: if potential cheaters lost the opportunity to cheat due to lack of knowledge, vigilance decreased by 20% “Intent” condition Hypothesis: People should be more wary of free loaders if they know the subject has the intent to cheat Subjects cued to possibility of intentional or accidental rule breaking; vigilance increased dramatically during “intent” condition but not “accidental” condition

Study Conclusion: Reciprocal altruism is an effective strategy for humans because we have evolved an advanced theory of mind and the necessary social cognitive strategies to root out and exclude free riders Reciprocal altruism is rare in the animal kingdom because most animals lack the necessary theory of mind to successfully prevent free riding