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| 79.3 - Spring 2006 | ||||||||||
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Lemurs Exhibit Capacity for Tool Use
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By Kanya Balakrishna
Unlike many primates, lemurs and other prosimian primates do not use tools in the wild. Nevertheless, recent findings suggest that they possess adequate learning and reasoning abilities for tool use, reports Laurie Santos, assistant professor of psychology, and colleagues in the Journal of Comparative Psychology. Their findings pose intriguing questions about the evolution and cognitive components of tool use.
Santos observed the behavior of two lemur species, Eulemur fulvus and Lemur catta, in a series of four experiments. The initial experiment allowed the subjects to use canes to access food placed out of their reach, which the lemurs quickly accomplished. In the second experiment, the tools were altered along one featural dimension, such as color, shape or size.
The subjects focused on changes that increased or decreased the utility of the tool, such as size, rather than functionally inconsequential changes in color or texture. This behavior showed that the lemurs understood the functional properties of the tools to the same degree as naturally tool-using primates, such as Capuchin monkeys.
The third and fourth experiments presented the lemurs with familiar and novel tools positioned in effective and ineffective orientations. The lemurs ignored the familiarity factor and were able to effectively manipulate both correctly and incorrectly positioned tools.Thus, the lemur’s ability to reason about the functional properties of different objects matches that of naturally tool-using primates. Then how to explain the absence of tool use in the wild?
Santos notes that although animals seem to comprehend the fundamentals of tool use, they do not necessarily understand how to apply that knowledge in the wild. She explains, “We are now thinking that what is important is not just an understanding of physics but an understanding of the intention to fulfill a goal.”
Psychologists call this ability “theory of mind”—the notion that people act because of innate knowledge of another individual’s mental state, a knowledge that cannot be derived. According to Santos, “There is now the question of whether non-human animals have this understanding as well.”
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