Date of Thesis

12-14-2014

Thesis Type

Masters Thesis

Degree Type

Master of Science

First Advisor

Peter G. Judge

Abstract

Tool use requires the manipulation of an object in the environment to achieve a goal, and the ability to relate one object to another. In the present experiments, I investigated tool use acquisition, and the relationship between tool use and self-control, in lion-tailed macaques (Macaca silenus). First, I examined three lion-tailed macaques' abilities to manipulate a tool by presenting a rake-shaped tool resting on a platform, with a food reward placed outside of the rake head. This experiment measured the monkeys' abilities to manipulate a rake-shaped tool, and investigated how the monkeys learned the tool-using skill. Two monkeys learned to successfully manipulate the tool to obtain the reward, while the other did not. In the second experiment, I investigated tool use in relation to self-control, by presenting a modified token-exchange task. In a trial, I presented one monkey that successfully learned to use the tool with a choice between a medium-value reward, and a rake tool that could be used to obtain a higher-value reward. If the monkey chose the tool over the food, I pushed a platform with a high-value food resting on it up to the caging that could be retrieved using the tool. The monkey began choosing the tool over the apple piece significantly more often than chance in his seventh 20-trial session. My results indicated that this monkey was capable of self-control using this novel design, as he chose the tool to retrieve the high-value reward over the low-value reward, even when there was a delay of up to 10 s between choosing the tool and retrieving the reward. This study was one of the first that investigated tool use acquisition and response inhibition in lion-tailed macaques. Performance of the two successful lion-tailed macaques on the tool acquisition task may reflect phylogenetic differences, in that they performed similar to another Old World monkey species (Macaca fuscata), but outperformed marmosets (Callithrix jacchus), a New World monkey species. Their capacity for self-control on this task was similar to that seen in both Old and New World monkey species.

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