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Analog number representations in mongoose lemurs (Eulemur mongoz): evidence from a search task
Kerrie P Lewis1, Sarah Jaffe, Elizabeth M Brannon
1Department of Anthropology, Washington University, St. Louis, MO 63130-4899, USA.
Animal Cognition
|January 22, 2005
Summary
Mongoose lemurs demonstrate numerical abilities, distinguishing quantities with a 1:2 ratio but not smaller differences. This suggests early primate number sense evolved before monkeys and apes.
Area of Science:
- Comparative psychology
- Primate cognition
- Evolutionary biology
Background:
- Monkeys and apes show numerical representation, suggesting early primate evolution of number sense.
- Prosimians, like the mongoose lemur, diverged from the lineage leading to monkeys, apes, and humans millions of years ago.
Purpose of the Study:
- To investigate the numerical capacities of the mongoose lemur (Eulemur mongoz).
- To determine if mongoose lemurs possess number representation abilities.
- To understand the evolutionary origins of numerical cognition in primates.
Main Methods:
- Subjects observed grapes being placed into a bucket, with some hidden via a false bottom.
- Search time in the bucket was measured to infer numerical representation.
- Control conditions assessed odor and grape quantity as potential confounds.
Main Results:
- Mongoose lemurs spent more time searching when food was expected but absent.
- Lemurs could discriminate quantities with a 1:2 ratio.
- Discrimination failed for ratios of 2:3 and 3:4, consistent with Weber's Law.
Conclusions:
- Mongoose lemurs possess numerical representations.
- These findings suggest number sense is present in early primate lineages.
- Numerical abilities in lemurs appear modulated by Weber's Law, indicating quantitative processing principles.