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Can chimpanzees (Pan troglodytes) discriminate appearance from reality?
Carla Krachun1, Josep Call, Michael Tomasello
1Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. ckrachun@gmail.com
Cognition
|July 28, 2009
Summary
Chimpanzees were tested on understanding that appearance can differ from reality. Some chimpanzees showed this cognitive ability, suggesting a key developmental milestone may be shared across species.
Area of Science:
- Cognitive Science
- Primatology
- Developmental Psychology
Background:
- The ability to distinguish between an object's appearance and its true reality is a crucial cognitive milestone.
- This capacity, known as appearance-reality understanding, has been extensively studied in human children.
Purpose of the Study:
- To investigate appearance-reality understanding in chimpanzees (Pan troglodytes).
- To conduct the first cross-species comparison of this cognitive ability.
Main Methods:
- A "Lens test" was adapted from child psychology procedures, using magnifying and minimizing lenses to alter the apparent size of grapes.
- The test included control conditions to rule out alternative explanations for performance.
Main Results:
- Significant individual differences in performance were observed among chimpanzees.
- Some chimpanzees demonstrated an understanding of the appearance-reality distinction.
- All chimpanzees failed a reverse contingency control, ruling out simple rule-learning.
Conclusions:
- This study provides the first direct evidence of appearance-reality understanding in chimpanzees.
- The findings suggest that this cognitive capacity may have evolved prior to the human-chimpanzee split.
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