Intuition, deliberation, and the evolution of cooperation

Adam Bear, David G. Rand
2016 Proceedings of the National Academy of Sciences of the United States of America  
Humans often cooperate with strangers, despite the costs involved. A long tradition of theoretical modeling has sought ultimate evolutionary explanations for this seemingly altruistic behavior. More recently, an entirely separate body of experimental work has begun to investigate cooperation's proximate cognitive underpinnings using a dualprocess framework: Is deliberative self-control necessary to reign in selfish impulses, or does self-interested deliberation restrain an intuitive desire to
more » ... operate? Integrating these ultimate and proximate approaches, we introduce dual-process cognition into a formal gametheoretic model of the evolution of cooperation. Agents play prisoner's dilemma games, some of which are one-shot and others of which involve reciprocity. They can either respond by using a generalized intuition, which is not sensitive to whether the game is oneshot or reciprocal, or pay a (stochastically varying) cost to deliberate and tailor their strategy to the type of game they are facing. We find that, depending on the level of reciprocity and assortment, selection favors one of two strategies: intuitive defectors who never deliberate, or dual-process agents who intuitively cooperate but sometimes use deliberation to defect in one-shot games. Critically, selection never favors agents who use deliberation to override selfish impulses: Deliberation only serves to undermine cooperation with strangers. Thus, by introducing a formal theoretical framework for exploring cooperation through a dual-process lens, we provide a clear answer regarding the role of deliberation in cooperation based on evolutionary modeling, help to organize a growing body of sometimesconflicting empirical results, and shed light on the nature of human cognition and social decision making. dual process | cooperation | evolutionary game theory | prisoner's dilemma | heuristics C ooperation, where people pay costs to benefit others, is a defining feature of human social interaction. However, our willingness to cooperate is puzzling because of the individual costs that cooperation entails. Explaining how the "selfish" process of evolution could have given rise to seemingly altruistic cooperation has been a major focus of research across the natural and social sciences for decades. Using the tools of evolutionary game theory, great progress has been made in identifying mechanisms by which selection can favor cooperative strategies, providing ultimate explanations for the widespread cooperation observed in human societies (1). In recent years, the proximate cognitive mechanisms underpinning human cooperation have also begun to receive widespread attention. For example, a wide range of experimental evidence suggests that emotion and intuition play a key role in motivating cooperation (2-5). The dual-process perspective on decision making (6-8) offers a powerful framework for integrating these observations. In the dual-process framework, decisions are conceptualized as arising from competition between two types of cognitive processes: (i) automatic, intuitive processes that are relatively effortless but inflexible; and (ii) controlled, deliberative processes that are relatively effortful but flexible. In many situations, intuitive and deliberative processes can favor different decisions, leading to inner conflict: Rather than being of a single mind, people are torn between competing desires. Despite the widespread attention that dual-process theories have received in the psychological and economic sciences (including incorporation into formal decision making models; refs. 9-11); the existence of related discussion in the theoretical biology literature regarding error management (12) (13) (14) , tradeoffs between fixed and flexible behaviors (15-18), and cultural evolution and norm internalization (2, 19, 20) ; and a long interdisciplinary tradition of arguments suggesting that strategies developed in repeated interactions spill over to influence behavior in one-shot anonymous settings (21-25), the dual-process framework has been almost entirely absent from formal models of the evolution of cooperation. Traditional evolutionary game theory models of cooperation focus on behavior, rather than the cognition that underlies behavior. Therefore, these models do not shed light on when selection may favor the use of intuition versus deliberation, or which specific intuitive and deliberative responses will be favored by selection. In this paper, we build a bridge between ultimate and proximate levels of analysis to address these questions, introducing an evolutionary game-theoretic model of cooperation that allows for dual-process agents. These agents interact in a varied social environment, where interactions differ in the extent to which current actions carry future consequences. To capture the tradeoff between flexibility and effort that is central to many dual-process theories, we allow our agents to either (i) use an intuitive response that is not sensitive to the type of interaction currently faced; or (ii) pay a cost to deliberate, tailoring their action to the details of the current interaction. Significance The role of intuition versus deliberation in human cooperation has received widespread attention from experimentalists across the behavioral sciences in recent years. Yet a formal theoretical framework for addressing this question has been absent. Here, we introduce an evolutionary game-theoretic model of dualprocess agents playing prisoner's dilemma games. We find that, across many types of environments, evolution only ever favors agents who (i) always intuitively defect, or (ii) are intuitively predisposed to cooperate but who, when deliberating, switch to defection if it is in their self-interest to do so. Our model offers a clear explanation for why we should expect deliberation to promote selfishness rather than cooperation and unifies apparently contradictory empirical results regarding intuition and cooperation.
doi:10.1073/pnas.1517780113 pmid:26755603 pmcid:PMC4743833 fatcat:yv4b7jshpjgdhlmabej5yhb6sm