Prosocial Behavior in Noncooperative Contexts
Some behavior that benefits others also occurs outside of the context of cooperation (although such behaviors may later lead to cooperative interactions). Such prosocial behavior cannot easily be explained by the three mechanisms mentioned previously. These behaviors include such acts as tipping in a restaurant to which you will never return, giving blood, and even voting, for which it is unlikely that any one person’s vote will be the deciding factor. These behaviors are common in humans (Eisenberg & Mussen, 1989) but also occur in other species (marmosets: Burkart, Fehr, Efferson, & van Schaik, 2007; capuchins: Lakshminarayanan & Santos, 2008; de Waal, Leimgruber, & Greenberg, 2008; Takimoto, Kuroshima, & Fujita, 2009; chimpanzees: Warneken, Hare, Melis, Hanus, & Tomasello, 2007; Warneken & Tomasello, 2006; although see Cronin, Schroeder, Rothwell, Silk, & Snowdon, 2009; Silk, Brosnan, Vonk, Henrich, Povinelli, Richardson et al., 2005; Vonk, Sarah, Brosnan, Silk, Henrich, Richardson et al., 2008; Jensen, Hare, Call, & Tomasello, 2006).
Despite the lack ofimmediate benefits, there are several potential functions to prosocial behavior. For instance, prosocial behavior may serve as a commitment device that demonstrates to others the actor’s dedication to equity, and thus their general merit as a social partner (Frank, 1988). Humans’ behavior supports this in some experimental settings; people will make decisions that lower their absolute and relative outcomes, presumably to send a signal to their partner (Yamagishi, Horita, Takagishi, Shinada, Tanida, & Cook, 2009). Related to this, prosocial behaviors may also improve one’s own reputation, providing benefits in the future (Milinski, Semmann, & Krambeck, 2002; Wenekind, 2000). In addition, helping others may avoid punishment or harassment that ensues if help is not given (Blurton-Jones, 1987). For instance, chimpanzees and other primate species harass food possessors, which makes the possessor more likely to share (Gilby, 2006; Stevens, 2004).
One mechanism that increases the chances of such prosocial behavior may be the “warm glow” people get from helping others (Andreoni,
1989; Batson, 1991), a mechanism that may be shared with other species (de Waal, Leimgruber, & Greenberg, 2008). This mechanism may encourage us to perform behaviors that benefit us in the long run despite the immediate costs (Brosnan, Salwiczek, & Bshary, 2010).
Capuchin monkeys are an interesting species to study with respect to prosocial and cooperative behaviors. First of all, they demonstrate both of these types of behaviors in the lab (see below for details). Moreover, many studies have been done investigating both types of behavior, and attempting to understand the tradeoffs the monkeys face as they make determinations whether or not to cooperate or share. Below I discuss what capuchin monkeys can tell us about the evolution of cooperation and prosocial behavior.