QUANTITY-BASED INTERFERENCE AND SYMBOLIC REPRESENTATIONS IN CHIMPANZEES (PAN-TROGLODYTES)

Five chimpanzees with training in counting and numerical skills select ed between 2 arrays of different amounts of candy or 2 Arabic numerals . A reversed reinforcement contingency was in effect, in which the sel ected array was removed and the subject received the nonselected candi es (or the number of candies represented by the nonselected Arabic num eral). Animals were unable to maximize reward by selecting the smaller array when candies were used as array elements. When Arabic numerals were substituted for the candy arrays, all animals showed an immediate shift to a more optimal response strategy of selecting the smaller nu meral, thereby receiving the larger reward. Results suggest that a res ponse disposition to the high-incentive candy stimuli introduced a pow erful interference effect on performance, which was effectively overri dden by the use of symbolic representations.