Categorization of above and below spatial relations by tufted capuchin monkeys (Cebus apella).

Using a matching-to-sample procedure, the researchers investigated tufted capuchins’ (Cebus apella) ability to form categorical representations of “above/below” spatial relations. In Experiment 1, 5 capuchins correctly matched bar-dot stimuli on the basis of the relative above and below location of their constituent elements. The monkeys showed a positive transfer of performance both when the bar-dot distance in the two comparison stimuli differed from that of the sample and when the actual location of the matching stimulus and the nonmatching stimulus on the apparatus was modified. In Experiment 2, the researchers systematically changed the shapes of the located object (the dot) or the reference object (the horizontal bar). These manipulations did not affect the monkeys’ performance. Overall, the data suggest that capuchins can form abstract, concept-like representations for above and below spatial relations.