Abstract

The social complexity hypothesis proposes that primates evolved large brains in order to master the challenges posed by a complex society. The more complex a social group, the more information an individual needs to remember and compute in order to successfully maneuver its social environment, particularly since with increasing group size, the number of possible dyads to keep track of is increasing exponentially. Accumulating evidence from field studies indicates that primates indeed keep track of their own dominance, kin and affiliative relationships with other individuals as well as of relationships between third parties, which indicates the capacity for triadic awareness. Studies are beginning to unravel how monkeys put this knowledge to use for their own benefit, i.e., when choosing reliable partners in cooperative acts like coalition formation. Several mechanisms underlying this social knowledge are currently discussed, as it is not clear whether nonhuman primates indeed possess the computational capacities to remember social interactions of all dyads in their social group. Emotional bookkeeping has been proposed as a cognitively less demanding mechanism to at least keep track of one’s own interactions—an idea gaining support by recent neuroendocrinological evidence.