Doing good does you good : Prosocial behavior as a sexual and social signal

How can evolutionary theories explain prosocial behavior that violates the premises of the inclusive fitness theory and the theory of reciprocal altruism? The basic idea underlying this thesis is that good deeds might evoke future benefits by signaling the qualities of an individual to third parties, ultimately increasing his or her value as a partner in a biological market. Together with Olga Stavrova, Julia Pradel, Thomas Schlosser, and Detlef Fetchenhauer, I examined the effects of isolated acts of prosocial behavior as signals of good character across four studies. Two determinants of the market value of an individual were considered: desirability as a mate (Chapter 2 and Chapter 3) and desirability as a cooperative partner (Chapter 4). Specifically, we explored the conditions under which isolated prosocial acts lead to considerable gains in the desirability as a mate or cooperative partner and the conditions under which such acts fail to have an effect. On the one hand, these conditions might reflect the structure of demand within specific subsets of biological markets (Chapters 2 and 3). According to sexual strategies theory (Buss, & Schmitt, 1993) and the theory of strategic pluralism (Gangestad, & Simpson, 2000), prosociality signals might differentially impact the market value of an individual as a short-term partner as compared to the market value as a long-term partner. On the other hand, there might be ambiguity due to different interpretations regarding the traits underlying specific signals (Chapter 4). Depending on situational circumstances and the person of the observer, the same act might be construed in terms of different traits, e.g., morality and competence, leading to different representations of the market value of an individual as a cooperative partner. Doing good has many facets. In the present research, however, we concentrated on three classes of prosocial behavior: altruism (Chapter 2), trustworthiness (Chapter 3), and trust (Chapter 4). In Chapter 2, we explored how signals of altruism shape perceptions of desirability in the short-term and long-term mate choices of females. According to the theory of strategic pluralism (Gangestad, & Simpson, 2000), most women possess distinct mate preferences allowing them to identify short-term partners with good genes and long-term partners with adequate partner or parenting characteristics. We presented video clips of male targets possessing various levels of physical attractiveness and provided counterbalanced information on the behavior of the targets in a one-shot dictator game. Female raters evaluated the targets with regard to the desirability as either short-term sexual or long-term romantic partners. Signals of altruism were more relevant for long-term rather than in short-term mate choices, whereas preferences for physical attractiveness were equally pronounced in both contexts. In addition, we observed that in long-term mating, displays of altruism had a larger effect on the desirability of physically attractive rather than unattractive targets. Chapter 3 extended the scope of our first study by accounting for both female and male preferences and further substantiating the interplay between signals of morality and physical attractiveness. Based on sexual strategies theory (Buss, & Schmitt, 1993) and a cognitive perspective of preferential mate choice (Miller, & Todd, 1998), we experimentally investigated the ways physical attractiveness and signals of moral virtue jointly shape perceptions of desirability in the long- and short-term mate choices of females and males. Silent video clips of target actors differing in physical attractiveness were presented to raters of the opposite sex who were provided with counterbalanced information regarding the decision of each target as a trustee in a one-shot binary trust game (previously validated as a suitable signal of moral virtue). The raters judged the desirability of the targets as either short-term sexual or long-term romantic partners. Physical attractiveness had a larger influence on desirability ratings in the short-term context, whereas moral virtue was more important in the long-term context. The preferences of males were more context-dependent, shifting more strongly towards physical attractiveness in the short-term context and moral virtue in the long-term context than the preferences of females. In the long-term context, physical attractiveness and moral virtue were mutually reinforced regarding their effects on perceptions of desirability. In Chapter 4, we examined the influence of trustful behavior on the value of individuals as cooperation partners. In general, people prefer cooperation partners that possess both the willingness and the ability to cooperate (Fiske, Cuddy, & Glick, 2007). However, trust is a double-edged sword; depending on the situation, trustful behavior might be perceived as self-interested or other-regarding, smart or gullible. Across two studies, noninvolved observers inferred personality traits from trustful versus distrustful behaviors in the context of a one-shot binary trust game. Considering the effects of social projection and consequentialism, we observed that trustful behavior was almost universally perceived more favorably than distrustful behavior with regard to fundamental dimensions of social judgment, namely warmth and competence, and with regard to overall evaluations of personality. These findings support the notion that displays of trust might serve as social signals, demonstrating the qualities of an individual as a cooperative partner. A short integrative discussion of the empirical research presented in Chapters 2 to 4 is presented in Chapter 5, and future research is outlined in Chapter 6.