Comparison of discrete ratios by rhesus macaques (Macaca mulatta).
Perceiving and comparing ratios are crucial skills for humans. Little is known about whether other animals can compare ratios. We trained two rhesus macaques (Macaca mulatta) to choose arrays that contained the greater ratio of positive to negative stimuli, regardless of the absolute number of stimuli in each of the two choice arrays. Subjects learned this task, and their performance generalized to novel ratios. Moreover, performance was modulated by the ratio between ratios; subjects responded more quickly and accurately when the ratio between ratios was higher. Control conditions ruled out the possibility that subjects were relying on surface area, although the ratio between ratios of surface area did seem to influence their choices. Our results demonstrate that rhesus monkeys can compare discrete ratios, demonstrating not only proportional reasoning ability but also the ability to reason about relations between relations.
Department of Neurobiology and Center for Cognitive Neuroscience, Duke University, Box 90999, Durham, NC, 27708, USA. caroline.drucker@duke.edu.
Caroline B
http://orcid.org/0000-0002-8215-506X
CB
Drucker
Department of Psychology and Neuroscience and Center for Cognitive Neuroscience, Duke University, Box 90999, Durham, NC, 27708, USA.
Marley A
MA
Rossa
Department of Psychology and Neuroscience and Center for Cognitive Neuroscience, Duke University, Box 90999, Durham, NC, 27708, USA.
Elizabeth M
EM
Brannon
D000818:Animals; D002755:Choice Behavior; D003071:Cognition; D003216:Conditioning, Operant; D004192:Discrimination, Psychological; D005260:Female; D008253:Macaca mulatta / Q000523:psychology*; D055641:Mathematical Concepts
Monkeys; Numerical cognition; Proportion; Ratios; Relations between relations; Rhesus macaques