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Abstract

In primates and other social mammals, opponents in aggressive conflicts have been reported to seek one another out after fights for various types of friendly interaction. In long-tailed macaques, these friendly reunions have been shown to restore aspects of the social relationship of the opponents to their preconflict state, and they have thus been interpreted as reconciliations. Although postconflict reconciliation would seem to be adaptive to gregarious animals that establish individualized social relationships, its occurrence is variable among species, groups and dyads. Some of this variation probably reflects costs and benefits of reconciling in different situations. One factor that might influence the benefit of reconciliation and hence its occurrence is the value of the social partner as a social or ecological resource: reconciliation should occur more often after fights with valuable social partners. We conducted an experiment to test this hypothesis using pairs of monkeys (Macaca fascicularis) as their own controls. First, baseline rates of reconciliation after experimenter-induced conflict were measured. Then, the value of the relationship, at least in the test context, was increased by training each pair of monkeys to perform a simple cooperative task in which each got access to food only if the partner fed nearby simultaneously. Finally, the reconciliation rate was measured again after training and compared to its baseline value. In 6 of 7 dyads, the reconciliation rate increased after training, and the median reconciliation rate after training was 3 times higher than at baseline. While the results are consistent with the value hypothesis, there are other potential explanations. Comparison of friendly behavior when there had been no prior aggression in baseline and post-training phases, however, suggested that the increase in reconciliation rate was neither the result of a general increase in compatibility nor the result of anticipated conflict in the cofeeding context.