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Ontogenetic and Phylogenetic Variation in Prosocial Behavior: Differences in Prosociality Across Human Development and Primate Species


Cooperation among genetic kin is a widespread phenomenon in nature, but this can't explain the widespread human motivation towards cooperating with non-relatives. This behavior is likely motivated both by evolved psychological mechanisms based on contingent reciprocity, and also by societally-varying cultural beliefs. In this dissertation I develop methods to explore the role of contingency and culture in human prosocial development, and the nature of prosociality across human and non-human primates. Chapter 1 investigates the development of contingent prosociality in American children, and chapter 2 charts the emergence of variation in prosociality across diverse societies. Chapter 3 develops methods for testing a range of prosocial behaviors in captive chimpanzees. These studies shed light on the motivations behind human cooperation, and the ontogenetic and phylogenetic origins of those motivations.

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