OUP UNCORRECTED PROOF – FIRSTPROOFS, Fri Dec 12 2014, NEWGEN PART 1 Prosocial Behavior at the Micro-Level Schroeder251014OUS_PC.indb 35 12/12/2014 4:36:53 PM OUP UNCORRECTED PROOF – FIRSTPROOFS, Fri Dec 12 2014, NEWGEN Schroeder251014OUS_PC.indb 36 12/12/2014 4:36:53 PM OUP UNCORRECTED PROOF – FIRSTPROOFS, Fri Dec 12 2014, NEWGEN CHAPTER The Evolutionary Psychology of 2 Human Pro-sociality: Adaptations, Byproducts, and Mistakes Pat Barclay and Mark van Vugt Abstract Evolutionary psychologists seek to understand prosocial behavior at four complementary levels of analysis: psychological mechanisms, development of those mechanisms (ontogeny), their adaptive or evolutionary function, and their evolutionary history (phylogeny). In terms of adaptive function, prosocial behavior is often costly to perform, so it is an evolutionary enigma. To evolve and be maintained, prosocial sentiment needs to bring corresponding fitness benefits. The authors outline a number of such evolutionary functions of prosocial behavior. Adaptive functions include direct benefits, mutualisms, stake or vested interests, kinship, reciprocity (direct and indirect), and costly signaling. Nonadaptive functions include mistakes, byproducts, and cultural learning. They provide a diagnostic tool for determining the likely function of any particular prosocial act and discuss three emerging perspectives in the study of prosocial behavior: scale of competition, multilevel selection, and biological markets. We conclude with future directions in evolutionary research on prosocial behavior. Key Words: altruism, cooperation, reciprocity, costly signaling, evolutionary psychology, levels of analysis Introduction selected against because they cause us to perform Humans are a prosocial species. People make behaviors that may be costly. Nevertheless, proso- substantial sacrifices to help their kin and sup- cial sentiments persist such that prosocial behavior port their friends, rescue complete strangers in is ubiquitous in human interactions and in many bystander emergencies, make large financial dona- nonhuman interactions, too. Why? This is the tions to charities, and defend their in-groups question that this chapter addresses. against outsiders (Dovidio, Pilliavin, Schroeder, & In this chapter, we start by clarifying two major Penner, 2006). Yet human prosociality is an evolu- sources of confusion over evolutionary explana- tionary puzzle because over time natural selection tions: differences in (1) definitions and (2) the will ruthlessly winnow out any traits that reduce an types of questions that are being addressed. We individual’s fitness (i.e., someone’s relative repro- then introduce a flowchart outlining a number of ductive success). Thus, for any costly trait to evolve potential factors that could cause prosocial senti- and persist, there need to be some corresponding ment to emerge, either because they have been ultimate benefits in terms of spreading the actor’s directly selected for through natural selection or genes. A first-pass glance at natural selection would because they are byproducts of other adaptations. suggest that prosocial sentiments should have been We briefly discuss some new perspectives that 37 Schroeder251014OUS_PC.indb 37 12/12/2014 4:36:54 PM OUP UNCORRECTED PROOF – FIRSTPROOFS, Fri Dec 12 2014, NEWGEN researchers are investigating and present some con- Researchers often get into unnecessary quarrels clusions and questions for future research. over the “causes” of prosocial behavior, without realizing that they may be providing valid answers Definitions to different questions (Barclay, 2011a; West et al., Prosocial behavior is defined as behavior “intended 2011). For example, one researcher may say “people to benefit one or more people other than oneself” help each other because they feel empathy.” A sec- (Batson & Powell, 2003, p. 463). This is a very broad ond researcher may say “people help each other term that includes many subcomponents, such as because they learn to help.” A third researcher will cooperation, mutualism, altruism, helping, and so say “people help each other because those who help on. Because different scientific disciplines use these tend to receive help.” A fourth research may say terms differently, we will simply provide the defini- “people help each other because we share this trait tions we are using and invite readers to substitute their with other apes and it evolved out of kin altruism.” preferred terms for these phenomena. That way, the What these researchers may not realize is that they focus is on the phenomena, not the semantics. We could all be right—or could all be wrong—because will use the term “prosocial behavior” to refer to any they are answering questions at different levels of actions that are intended to benefit others, regard- analysis. Nobel prize-winning ethologist Niko less of whether the actor also benefits in the process. Tinbergen (e.g., 1968) introduced his four levels of We will use the more popular word “helping” syn- analysis to clarify the different types of questions onymously with “prosocial behavior.” We will use the and avoid unproductive debates over explanations term “prosocial sentiment” to refer to any emotions at different levels. or psychological mechanisms that trigger this help- In our example, the first researcher is talking ing. Some types of prosocial behavior are costly to about proximate psychological mechanisms, that the actor, at least temporarily (“costly cooperation”), is, what is going on within the individual at the whereas other types of prosocial behavior carry no time he or she helps. The second research is talking costs or provide return benefits to the actor almost about development, that is, how that psychological immediately (“noncostly cooperation”). Biologists use mechanism (whatever it happens to be) develops the term “altruism” to refer to actions which decrease within the life span of an individual and how genes one’s lifetime reproductive success, and it is one form and environments interact. The third researcher of costly cooperation (West, El Moulden, & Gardner, is asking about ultimate function, that is, why an 2011). A mutualism is a form of (noncostly) coopera- individual would develop in such a way as to have tion when the actor and another agent both benefit that psychological mechanism, what the benefits of from something the actor does. This could include having it are, and what selective pressures cause it active coordination between the two of them but does to persist. The fourth research is addressing phylog- not need to. Those who disagree with our terminology eny or evolutionary history, that is, how and when should simply substitute their own where appropriate. the mechanism evolved in our evolutionary history, and what prior trait(s) it evolved from. Levels of Analysis: What Question(s) Are Our example shows how these four levels of We Addressing? analysis are complementary, not mutually exclu- Evolutionary psychology draws from many dis- sive: all behaviors require an explanation at all four ciplines, including but not limited to evolutionary of these levels of analysis to be fully understood. biology, experimental economics, mathematical The only fruitful scientific discussion is between game theory, anthropology, and of course psy- explanations within the same level. For example, chology (social, developmental, cognitive, etc.). researchers can debate whether the psychologi- It uses tools and methods from all of these to cal mechanism that triggers helping behavior is investigate behavior. As such, evolutionary psy- empathy versus “oneness with others” (e.g., Batson chology is not a field or subdiscipline in the tradi- et al., 1997, versus Cialdini et al., 1997). They can tional sense. Instead, it is a meta-theoretical stance also debate development by asking whether that which can be applied to any field, subdiscipline, psychological mechanism is learned versus innate or topic (Daly, 2011; Van Vugt & Schaller, 2008). (though this is actually a false dichotomy, see What often differentiates evolutionary researchers Ridley, 2003). When debating adaptive function, from nonevolutionary researchers is the types of researchers can argue over whether prosocial behav- questions they ask, and how those questions are ior serves to invite reciprocation or serves to signal interconnected. desirable qualities. For phylogeny, we can discuss 38 The evolutiOnary Psychology Of human PrO-sOciaLity Schroeder251014OUS_PC.indb 38 12/12/2014 4:36:54 PM OUP UNCORRECTED PROOF – FIRSTPROOFS, Fri Dec 12 2014, NEWGEN whether our prosocial sentiments are unique to the being prosocial increases one’s inclusive fitness (i.e., human lineage versus evolutionarily ancient, and spread of one’s genes). Nonadaptive explanations are we can debate which other sentiments they evolved ways in which prosocial behavior could spread even from. However, we cannot, for example, say that if they do not increase one’s fitness: for example, the because prosociality is learned, it therefore does not behavior could be a byproduct of some other adap- function to invite reciprocation, because these are tive mechanism or it could be a mistake produced explanations at different levels (e.g., the reciproca- by a prosocial psychology that is adaptive on aver- tion could be the reinforcer that causes prosocial- age (or once was). Some of these explanations have ity to be learned). Much of the controversy over received more attention than others, but it does not evolutionary explanations