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Abstract
Nut-cracking is a complex tool use behavior that has only been discovered in wild chimpanzees and capuchin monkeys. The study of animal tool use has long emphasized the cognitive processes such as reasoning and representation in tool use but has largely ignored the act of too use itself. This research employs a Perception-Action perspective derived from the Gibsonian Ecological Psychology framework to study the selection and adaptive use of materials in nut-cracking by wild capuchin monkeys in Brazil. I first reviewed the background literature on the study of animal tool use and compared the traditional representational approach and the proposed Perception-Action perspective (Chapter 1). Next I presented the first study in which capuchin monkeys selectively used effective novel pits on anvils, using exploratory behaviors to detect affordances (Chapter 2) and the second study in which the capuchin monkeys adaptively and effectively used hammer stones of different weights to crack nuts by modulating forces and lifting height (Chapter 3). Chapter 4 summarized the findings and discussed the significance of the Perception-Action perspective in the study of animal tool use and problem solving.