Lemurs and macaques show similar numerical sensitivity
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We investigated the precision of the approximate number system (ANS) in three lemur species (Lemur catta, Eulemur mongoz, and Eulemur macaco flavifrons), one Old World monkey species (Macaca mulatta) and humans (Homo sapiens). In Experiment 1, four individuals of each nonhuman primate species were trained to select the numerically larger of two visual arrays on a touchscreen. We estimated numerical acuity by modeling Weber fractions (w) and found quantitatively equivalent performance among all four nonhuman primate species. In Experiment 2, we tested adult humans in a similar procedure, and they outperformed the four nonhuman species but showed qualitatively similar performance. These results indicate that the ANS is conserved over the primate order.
KeywordsNonhuman primates Numerical cognition Comparative psychology Number discrimination Weber fraction Prosimians
We thank the Duke Lemur Center, Monica Carlson, and the many research assistants who assisted with this research. We thank members of the Brannon laboratory for their helpful discussion of these data. This work was supported by a National Science Foundation CAREER award (No. 0448250) to Elizabeth M. Brannon.
Conflict of interest
The authors declare that they have no conflict of interest.
The experiments reported here comply with the current laws of the United States of America.
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