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An anthropomorphous ape, if he could take a dispassionate view of his own case, … might insist that they were ready to aid their fellow-apes of the same troop in many ways, to risk their lives for them, and to take charge of their orphans; but they would be forced to acknowledge that disinterested love for all living creatures, the most noble attribute of man, was quite beyond their comprehension.

Charles Darwin, The Descent of Man, 1871, p. 105

Humans have for centuries sensed that we share with animals the motivation to form close, enduring social bonds. Recent research has not only confirmed these intuitions but has also begun to uncover the many fitness benefits of such bonds (Silk and House, Chapter 16, this volume). Nevertheless, despite many similarities in patterns of cooperation between humans and other animals, there are also important differences in its quality and scope. The reasons for these differences remain topics of debate, in large part because we still do not understand the full range of animals’ cognitive abilities, in what ways these abilities differ from humans’, and how these abilities contribute to the formation of cooperative bonds. Many animals share with humans the ability to monitor other individuals’ friendships and animosities, to remember the nature of recent interactions, and perhaps also to recognize other individuals’ motivations and intentions. Whether they recognize more complex mental attributes like the intent to deceive, however, remains unclear, as does the extent to which animals share humans’ sometimes hyperbolic motivation to engage others in cooperative ventures.


Many social animals live in groups containing both kin and nonkin, in which interactions are simultaneously competitive and cooperative and in which individuals maintain differentiated relationships with a subset of group members. To navigate through this complex network of relationships, it seems essential to be able to monitor not only one’s own interactions but also the interactions of others. The ability to acquire and use information about other individuals’ social relationships permits individuals to assess the strength of allies and opponents, to reconcile with opponents, and to choose mates, and it appears to be under strong selective pressure. Indeed, there is now an extensive literature indicating that animals are highly motivated to learn about other individuals’ relationships and competitive abilities. Knowledge of other individuals’ dominance ranks has been demonstrated in a variety of species, including not only primates and other social animals like pinyon jays

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