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Gulledge / Poster

Evidence for rhesus monkeys' concept of number

Gulledge,Jonathan P., Washburn, David A. & Rumbaugh, Duane M.
Language Research Center, Georgia State University

     Do rhesus monkeys (Macaca mulatta) have the capacity to determine relative numerosity in a choice discrimination between Arabic Numerals and random dot arrays? The numerical abilities of rhesus monkeys’ were assessed utilizing a computerized relative numerousness paradigm. During the training phase of the experiment five monkeys were each presented with two types of trials, numeral-to-numeral comparisons and random dot array-to-random dot array comparisons. The monkeys were required to determine which of the two arrays represented the greater quantity by bringing the cursor into contact with the stimulus through manipulation of a joystick. The monkeys were rewarded regardless of the stimulus chosen, responses were deemed correct only if the greater quantity stimulus was selected. After a criterion level of accuracy was met (75% correct over the last 100 trials) participants proceeded to the testing phase. During the testing phase participants were again required to select the greater quantity stimulus, however, novel probe trials requiring the monkeys to choose between an Arabic numeral and a random dot array were randomly interspersed with trials like those of the training phase. All monkeys performed this task at levels significantly in excess of chance. Given that these monkeys demonstrated an ability to represent quantity accurately across stimulus types (i.e. from Arabic numerals to random dot arrays) they can be said to have a concept of number.