Preface

How do we explain the ubiquity of prosocial behavior among humans, when nature is “red in tooth and claw?” How come a person can be sometimes generous, helpful, and cooperative, yet other times self-absorbed, rude, or even abusive? This puzzle, of enduring interest in both the social and the biological sciences, has elicited much scientific collaboration along with heated discussion and conflicting opinions. The discord exists in part because prosocial behavior can be studied at different levels of analysis. On the one hand, ultimate causes of prosociality focus on the selection pressures that have shaped human behavior to respond adaptively in social interactions. On the other hand, proximate explanations try to interpret the human psychology and address the mix of motivations that drive individuals to make decisions according to hic et nunc conditions.

The new and growing field of neuroeconomics has much to offer with respect to solving the prosociality paradox by creating a bridge between these two levels of analysis: at the proximate level, the (un)cooperative choices people make are driven by neural activation corresponding with the leading motivation at that time. But ultimately, the pattern of neural activation underlying any behavior is generated by a brain and evolutionary conserved neuropeptide systems that have been continuously molded over many generations to match different environmental pressures. In addition, brain plasticity allows for socialization and learning, fine-tuning decision making in accordance with local conditions. The result is a brain that is wired to accommodate multiple sets of information at the same time, filtering out those behaviors that prove to yield—on average—the highest fitness gain.

This book summarizes the existing evidence for the hypothesis that, at the proximate level, prosocial decisions are driven by the anticipation of reward, which can be economically lucrative or emotionally pleasing. The value attached to cooperation is established in the brain’s reward system, which receives input from a cognitive control system computing the benefits to the self, and a social cognition system (“the social brain”), which is sensitive to subtle social information regarding the cooperative intentions of others. Which of the two systems will prevail in the decision-making process will depend on the local conditions (the presence or absence of incentives and the perception of trustworthiness of others) and any preexisting tendencies (or preferences) to behave either prosocially or selfishly. Ultimately, evolution created neither a cooperative nor a selfish default, but a brain that steers decision making toward the most valued outcome. These values are subject to change, giving each one of us the potential to hover between compassion and egoism.

Our study adds a new angle to the century-old debate regarding human nature and the processes that govern human reasoning. The propositions in this book suggest that the concept of “rationality,” when it comes to cooperative behavior, should not be interpreted without considering an individual’s intrinsic values. Rational behavior is relative. In repeated social interactions, the benefits of cooperation, whether through synergy, accumulating profits, or through (in)direct reciprocity, can be established, making prosocial behavior economically rational. But in the absence of such benefits, prosocial behavior should not necessarily be considered an “irrational” by-product of behavior in repeat interactions. Humans do not willingly forsake their own well-being. They never intend to lose, and therefore avoid exploitation as much as possible by constantly and intuitively gauging the social environment for potential traitors. Within the boundaries of one’s intimate group, the “warm glow of giving” and the “need to belong” can make cooperation socially rational. But individuals who are intrinsically motivated to act prosocially and consequently enjoy the emotional as well as collective benefits of mutual collaboration are also able to reverse this behavior when they sense it is no longer adaptive.

The neuroeconomic framework is what differentiates this book from other works on this topic. By combining the experimental paradigms from game theory with neuroimaging techniques, it has become possible to open the “black box” of human decision making. Through a joint effort of psychologists, neuroscientists, and behavioral economists, the latent drivers of choice behavior have been revealed experimentally, corroborating the interplay of both affective and cognitive processes that influence conscious deliberation as well as heuristic decision making. With this approach, we hope to fine-tune the “rational choice” behind cooperation and we put forth the proposition that prosocial decision making balances both economically and socially rational motives.

The book is divided into five parts. In Chapter 1, “Two Routes to Cooperation,” we define various types of prosocial behaviors and point to their origins and universality. We summarize the generalizations that have emerged from field studies and laboratory experiments in behavioral economics and social psychology. We note that the extant literature comprises two, mostly independent, streams of research that have revealed two fundamentally different logics behind cooperation, one claiming that cooperation is economically rational, the other that it is socially rational. These two logics are the result of distinct motives that are present within each individual. Following the economically rational route to cooperation, people are motivated to pursue self-interest, but cooperate readily when self-interest coincides with collective interest. This research stresses the importance of extrinsic incentives, such as pay-offs, synergy, accumulating benefits, reciprocity, and reputation benefits. Following the socially rational route, people strive for group inclusion, and cooperation is an effective way to strengthen belonging, build social networks, and avoid ostracism. Social norm internalization and trust are especially important here.

In Chapter 2, “The Neuroanatomy of Prosocial Decision Making,” we draw on research in neuroeconomics to substantiate that the brain is wired for both an economic and a social rationality. We summarize the results of a number of experiments showing that economically and socially rational choices are rooted in different neural networks that operate in concert and independently modulate decision making. Prosocial decisions can be explained as motivated choices that yield either economically or socially valuable rewards. These choices are contingent on the presence of extrinsic rewards that align self-interest with collective interest and/or trust signals that minimize the chance of exploitation. We identify three brain systems that are consistently recruited when people face ambiguous situations that call for cooperation. These are the neural networks dedicated to reward processing, cognitive control, and social cognition. We propose that these three brain systems are linked together in such a way that an (un)cooperative decision is the result of the modulatory influences of cognitive control and social cognition on the reward-processing system of the brain.

In Chapter 3, “The Neurochemistry of Prosocial Decision Making,” we elaborate on the neural networks that are responsible for generating (un)cooperative decisions, and devote this chapter to the contribution of neurotransmitters. Recently, much attention has been given to the role of the neuropeptide oxytocin in regulating social interaction. Oxytocin is likely to facilitate socially rational prosocial decision making by reducing social anxiety, increasing empathy, and by linking it to the capacity to experience reward from social interaction. In addition, oxytocin is likely to promote behaviors that benefit the group. The monoamines dopamine and serotonin also have documented roles in decision making, especially with respect to reward processing. These neurotransmitters are also crucial in sustaining cognitive control. However, in the domain of social decision making, especially serotonin, more than dopamine, is likely to contribute to economic rationality.

In Chapter 4, “Individual Differences in Prosocial Decision Making,” we address the extensive heterogeneity in social values that suggest that social and economic rationality do not have to be expressed equally in all individuals. Temperamental dispositions combined with experience-based differences in social learning may lead to stable differences in values that are tracked by idiosyncratic activation patterns of the brain’s reward system. Values are a compass that help people navigate through the social world: they determine which environmental information people will more likely attend to, influencing the degree to which networks dedicated to cognitive control or social cognition will be recruited in the decision-making process. The end result is that each individual develops his or her own neural signature that facilitates or hampers cooperation.

To conclude, in Chapter 5, “Beyond Parochialism: Cooperation across the Globe,” we address a darker side of prosocial behavior. Cooperation heuristics that are economically or socially rational within the boundaries of a particular social group tend to bias decision making in favor of same-group members. When the group is threatened, such parochial behavior may turn into more extreme forms, including ethnocentrism, racial discrimination, political...