Transition between sensorimotor and symbolic activities in nursery-reared chimpanzees ( Pan troglodytes)

Abstract

Bates's (1979) and Piaget's (1945) work with infants have demonstrated that language is not the only form of symbolic activity. These researchers however, have done more than identify other forms of symbolic behavior, they have suggested that some particular behaviors such as tool-use, object permanence and deferred imitation play a major role in the emergence of symbols. If language is only one form of symbolic activity, then it becomes possible to study other forms of symbolic behavior such as the one displayed in symbolic play. Some researchers ( Dasen et al., 1978 ; Inhelder et al., 1972 ) have studied the emergence of functional play and the beginnings of symbolic play. The results of these studies provide a framework of the human child's behavior during the period of transition between the sensorimotor and symbolic activities. On the other hand, the observation of chimpanzees in their natural environment and in captivity have shown that most of the behaviors identified as prerequisites in the emergence of language (e.g. tool-use, object permanence, etc …) are already present in this species. Until now however, studies have been oriented around language acquisition rather than on other forms of symbolic behavior. The purpose of this research is to determine if nursery-reared chimpanzees can display any type of symbolic behavior as human children do when they are interacting with objects normally present in their environment. Three different experiments were conducted over a four year period using a methodology for human children. The four subjects, however, were exposed to modeling sessions before each of the videotaping sessions in the last experiment because of their low levels of functional play in the previous experiments. Results have shown major differences between the chimpanzee and the human child. More specifically, the chimpanzee does not seem to reach the stage of transition between the sensorimotor period and the symbolic activity because of its low levels (when compared with the human child) of: (i) conventional use of objects; (ii) activities with two objects or more; (iii) ambiguous activities. Morcover, symbolic play is never observed during the experiments. Deferred imitation (e.g. conventional use of objects) thus seems to be the highest level of cognitive complexity displayed by the chimpanzee in the context of free play.