The Self-organization of Social Complexity in Group-Living Animals

Abstract

This review demonstrates that many patterns of complex social behavior in group-living animals, in particular primates, may emerge by self-organization from cognitively “simple” competitive and affiliative interactions among group members. We focus on the lessons learnt from the different versions of model DomWorld. In these computational models, virtual individuals are group-living, initiate aggression in a risk-sensitive way, and groom others if they think they will be defeated. We show that, unexpectedly, in these models almost all social patterns emerge automatically that have been assumed to be displayed for cognitively more sophisticated reasons. For example, the emerging triadic agonistic patterns comprise all types of coalitionary support (conservative, bridging, and revolutionary), its reciprocation, and reciprocation of contra-support or opposition. Further, grooming is reciprocated, exchanged for support, and shown in patterns of post-conflict affiliation, including those of “reconciliation” and “consolation,” with similar differences between a tolerant and intolerant dominance style as in empirical data. These patterns emerge mainly because agonistic interactions create a spatio-social structure within groups that influences the occurrence of other social interactions in unexpected ways. When these dominance interactions in the computer model are based on the winner-loser effect, inter-sexual dominance relations appear to depend on sex ratio and intensity of aggression. Females become more similar in rank to males the fiercer the aggression among group members is and, in groups with intense aggression, the more male-biased the Adult Sex Ratio is. Similar empirical patterns have been reported for fish, primates, and humans. In conclusion, the DomWorld models illustrate how individual-based models provide an excellent tool for finding cognitively simple explanations for complex patterns of social behavior. These models generate nonintuitive results by integrating social interactions and their consequences across different levels, i.e., those of the individual, relationships, and group.