The social facilitation of manual activity in capuchin monkeys (Cebus apella)
Crast, Jessica Lynn
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Young animals of many species, such as chimpanzees and capuchin monkeys, practice foraging skills for several years before acquiring proficiency, during which time practice rarely yields a food reward. Previous research has not investigated why, at the proximate level, youngsters spend so much time and physical effort without extrinsic reward. The purpose of this dissertation was to investigate the hypothesis that practice on a foraging problem is socially facilitated. To do so, manual activity with a foraging apparatus (Study 1) and with a toy unrelated to food (Study 2) was investigated in eight adult male capuchins under conditions that previous research has shown facilitate eating. The subjects’ manual activity was measured as the following social factors were varied (experimental phases of Studies 1 and 2): 1) Partner Behavior (specifically, the effects of partner presence, eating behavior, and simultaneous working behavior on the same foraging apparatus or non-food toy), 2) The number of partners present (i.e., specifically, the effects of one partner vs. seven partners), 3) Competition with a partner for access to the foraging apparatus, and 4) Visibility of partners (i.e., the effects of being able to see and hear others’ behavior vs. only hear them). The results failed to support the hypotheses that manual activity would be socially facilitated by the above mentioned social conditions. The lack of social facilitation of manual activity implies that engagement in a manipulative task is intrinsically motivating in capuchins.