Animal Thinking: Contemporary Issues in Comparative Cognition

15 Simple Reactions to Nearby Neighbors and Complex Social Behavior in Primates

15 Simple Reactions to Nearby Neighbors and Complex Social Behavior in Primates Charlotte K. Hemelrijk Abstract Simple behavioral reactions to nearby neighbors may result in a greater variety of patterns of social interactions, social relationships, and social organization than has been previously assumed. Here, such transitions of micro-rules to macro-patterns are shown for primates in computer models. They concern the emergence of patterns of aggression, including the formation of coalitions and patterns of affiliation, such as reconciliation and grooming reciprocation. It is generally believed that these behavioral patterns require high cognition. While the high cognitive capacities of primates are not denied, these simulations suggest that primates may be less calculative in their daily lives. Simple behavioral reactions and self-organization may suffice to explain their patterns of social behavior. Introduction Compared to many other animal taxa, the social behavior of primates is generally regarded to be more complex in its patterns and underlying cognition. This complexity has often been overestimated, because the same patterns of social behavior are found in taxa that are supposed to be cognitively less sophisticated and recently, for these patterns, cognitively simpler explanations have been given (discussed below). In earlier empirical studies, coalitions of primates were considered more complex than those of other species, and this was taken as evidence of calculative behavior (Harcourt and de Waal 1992). In later studies, however, coalitions of hyenas proved to be similar (Smith et al. 2010), and coalitions of 224 C. K. Hemelrijk primates were found to be explainable by simple behavioral rules (Range and Nöe 2005). The same holds for patterns of affiliative behavior in primates. Whereas early empirical studies suggested that affiliative patterns, such as reconciliation and reciprocation, require sophisticated cognitive deliberations (de Waal 1982), they were later found in species presumed to have less sophisticated cognition, such as goats, hyenas, and dolphins (Aureli and de Waal 2000). The mechanisms thought to underlie reconciliation (a conciliatory tendency , the “deliberation” to reconcile fights with more valuable partners more often, and the ability to distinguish between relationships of different value; Aureli and de Waal 2000) were later considered too complex for these animals (Silk 2007a). Furthermore, record keeping and “moralistic feelings” in primates were initially thought to be the basis of reciprocation and exchange (de Waal 1982); later simple behavioral responses were proposed to explain the observed patterns of behavior (Hemelrijk 1996a). Thus, empirical explanations proceed from assuming complex deliberations to simpler behavioral rules. This transition from cognitively complex causes to simple ones is also observed in studies of artificial intelligence, for example, in computer models and the building of robots (Pfeifer and Scheier 1999). It appears that the discovery of cognitively simpler explanations is furthered by the use of self-organization models (Camazine et al. 2001; Hemelrijk 2002, 2005). In this chapter, I discuss to what extent complex patterns of social behavior can be generated without resorting to sophisticated cognition and how they may arise through self-organization from spatial interactions among individuals who follow simple behavioral rules. To avoid the confusion that often surrounds these models, I indicate from the outset what these models can and cannot achieve. The models presented in this chapter are a kind of “null model”: they show that little cognition is needed for primates to generate the observed patterns of social interaction. If simple behavioral reactions can generate certain complex patterns similar to those observed in primates, then this complex behavior can no longer be seen as proof of the sophisticated higher-level cognition that has been presumed to underlie it. Thus, these models illustrate that even if primates have sophisticated cognition (such as, possibly, “knowledge” about social relationships of others), they may not use it in (most of) their daily behavior. This also holds for humans. These models cannot rule out the possibility that complex cognitive processes are used in these social interactions. They show, however, that explanations may be more parsimonious and cognitively simpler explanations should be preferred. Social Organization, Interactions, and Relationships Primates are supposed to use their highest cognition in their aggression, such as their coalitions, and affiliative behavior, such as in exchange and reciprocation of services and in reconciliation of fights (Byrne and Whiten 1997). The Simple Reactions and Complex Social Behavior in Primates 225 model, DominanceWorld, and its extensions, GroupWorld and GroofiWorld, show, however, that these behavioral patterns may arise from simple social habitual...