Rhesus monkeys (Macaca mulatta) spontaneously compute addition operations over large numbers
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Updated: Aug 15, 2026

Behavioral Assessment of Manual Dexterity in Non-Human Primates
Published on: November 11, 2011
Jonathan I Flombaum1, Justin A Junge, Marc D Hauser
1Department of Psychology, Yale University, Box 208205, New Haven, CT 06520-8205, USA. jonathan.flombaum@yale.edu
Abstract:
Mathematics is a uniquely human capacity. Studies of animals and human infants reveal, however, that this capacity builds on language-independent mechanisms for quantifying small numbers (<4) precisely and large numbers approximately. It is unclear whether animals and human infants can spontaneously tap mechanisms for quantifying large numbers to compute mathematical operations. Moreover, all available work on addition operations in non-human animals has confounded number with continuous perceptual properties (e.g. volume, contour length) that correlate with number. This study shows that rhesus monkeys spontaneously compute addition operations over large numbers, as opposed to continuous extents, and that the limit on this ability is set by the ratio difference between two numbers as opposed to their absolute difference.
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