Multiple classification performance of juvenile chimpanzees, normal children, and retarded children

Abstract

The cognitive capacities of juvenile chimpanzees, normal children, and retarded children were evaluated by using a nonverbal, Piagetian-type multiple classification task. The three groups of subjects were tested with the same two by two stimulus matrix, which was formed by combining two different colors with two different shapes. On each problem the subjects were required to select one of four stimulus items from the response tray and place it inside the empty cell of the stimulus matrix. It was found that the human and nonhuman primates tested were able to select objects with correct color and shape cues (C+/S+)significantly more often than the other objects with only color cues correct (C+/S-), only shape cues correct (C-/S+), or neither cue correct (C-/S-). Although the two groups of human children were able to select the C+/S+ objects about 100% of the time by the end of testing, the normal children required significantly fewer problems than the retarded children. The juvenile chimpanzees needed significantly more problems than the human subjects before they consistently selected the C+/S+ object on the first trial and attained a level of correct responding that was above chance. Moreover, their level of performance did not exceed 70% correct. These data suggest that the human children (both normal and retarded) used a conceptual strategy, while the juvenile chimpanzees employed a perceptual strategy to solve the multiple classification problems. The relationship between language and conceptual problem-solving strategies for Piagetiantype tasks is discussed.