Monkeys' Performance on Ambiguous-Cue Problems

Abstract

9 experimentally naive rhesus monkeys were tested on ambiguous-cue problems involving three stimuli: P, the positive or rewarded stimulus; N, the negative or nonrewarded stimulus; and A, the ambiguous stimulus which is nonrewarded when paired with P, but rewarded when paired with N. Either the NA pair or the PA pair was presented on every trial. All Ss were tested with two types of stimuli, planometric plaques and stereometric objects. The results corroborate apparently conflicting previous reports of performance by primates on ambiguous-cue problems with these two types of stimuli. That is, performance on PA trials was superior to performance on NA trials with plaque stimuli, but the converse was obtained with objects. A differential S-R spatial discontiguity inherent in only the plaque version of the problem was identified as one cause of the discrepant results.