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Degree

Doctor of Philosophy, Ohio State University, Psychology, 2010.

Abstract

While the cognitive capacities of primates have been studied for nearly a century, it is only relatively recently that scientists have begun to systematically compare the cognition of non-human primates with one another, humans, and other animals. These comparisons have been used to formulate hypotheses on the nature of cognitive change that may have led to human cognition. Knowledge about which species share cognitive characteristics can be used to understand why these characteristics exist and how they are used within their natural environments. Chimpanzees have long been the model subject, as they are the closest living relatives to humans and exhibit many complex behaviors in their natural environments and in captivity; among monkeys, capuchins have been most studied for similar reasons. It has become increasingly difficult to understand the full picture of non-human primate cognition, however, based on a limited number of species. With this in mind, it is useful to test a range of primates to pinpoint cognitive similarities and differences among groups. Gibbons are an important subject in this regard, as their cognition has received very little study, yet they occupy a unique phylogenetic position as lesser apes, which diverged from a common human ancestor between the time of Old World monkeys and great apes. In the present research, a range of physical and social cognitive tests were used to gain a better understanding of gibbon cognition. In the domain of physical cognition, gibbons were tested in the areas of quantity and causality. Results on numerosity comprehension indicate that gibbons’ dicriminability threshold likely falls between that of chimpanzees and rhesus macaques, although further study is needed to confirm this. In the causality experiments, gibbons were successful in using changes in an object’s shape to locate hidden food (Experiment 2B). They were less successful in Experiment 2C, however, especially with variations on the basic support problem and they also had difficulty utilizing noise to locate hidden food in Experiment 2A. In the second set of experiments, gibbons were tested in the domain of social cognition, specifically in the areas of communication and theory of mind. They were much less successful in this group of studies. The gibbons were not able to utilize the communicative cues of the experimenter to locate a hidden reward whether they were provided in a basic informative context (Experiment 3A) or a more intentional one (Experiment 4B). While they were able to indicate the location of a reward to a naïve experimenter in Experiment 3B, they failed to attend to the attentional state of the experimenter in Experiment 3C. In addition, in Experiment 4A they were able to follow combined head and eye gaze, yet failed to follow eyes alone or follow head/eye gaze behind a barrier. Based on these results, gibbon cognition seems to have important differences from that of great apes and more generally resembles that of monkeys. Implications of this research and areas for future study are discussed.

Subject Headings

Psychology

Keywords

gibbon; cognition; number; causality; communication; theory of mind

Committee / Advisors

Sarah Boysen, PhD (Advisor)
Vladimir Sloutsky, PhD (Committee Member)
Dawn Kitchen, PhD (Committee Member)

Pages

118p.

Document number: osu1285083190
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1285083190

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