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Full-Text Articles in Behavior and Ethology
Evolutionary Pressures On Primate Intertemporal Choice, Jeffrey R. Stevens
Evolutionary Pressures On Primate Intertemporal Choice, Jeffrey R. Stevens
Department of Psychology: Faculty Publications
From finding food to choosing mates, animals must make intertemporal choices that involve fitness benefits available at different times. Species vary dramatically in their willingness to wait for delayed rewards. Why does this variation across species exist? An adaptive approach to intertemporal choice suggests that time preferences should reflect the temporal problems faced in a species' environment. Here, I use phylogenetic regression to test whether allometric factors (relating to body size), relative brain size, and social group size predict how long 13 primate species will wait in laboratory intertemporal choice tasks. Controlling for phylogeny, a composite allometric factor that includes …
The Selfish Nature Of Generosity: Harassment And Food Sharing In Primates, Jeffrey R. Stevens
The Selfish Nature Of Generosity: Harassment And Food Sharing In Primates, Jeffrey R. Stevens
Jeffrey Stevens Publications
Animals may share food to gain immediate or delayed fitness benefits. Previous studies of sharing have concentrated on delayed benefits such as reciprocity, trade and punishment. This study tests an alternative model (the harassment or sharing–under–pressure hypothesis) in which a food owner immediately benefits because sharing avoids costly harassment from a beggar. I present an experiment that varies the potential ability of the beggar to harass, and of the owner to defend the food, to examine the effects of harassment on food sharing in two primate species: chimpanzees (Pan troglodytes) and squirrel monkeys (Saimiri boliviensis). For …