Generalization between productive use and receptive discrimination of names in an artificial visual language by a chimpanzee

In a computer-controlled artificial visual language by a chimpanzee, early development of the interaction between responses of two language modes,productive use and receptive discrimination, was investigated. In Experiment 1, receptive discrimination was established for the names of five colors and three objects which had been accurately used in the productive mode, and the result suggested that receptive learning develops independently of productive learning. After intramodal generalization of these names was shown by unreinforced probes in each mode in Experiment 2, intermodal generalization of 12 additional names, 6 in each direction,was examined in Experiment 3. A pair of color or object names was taught in one mode until its intramodal generalization was shown to be adequate and then transferred into the other mode. Two pairs concurrently examined in opposite directions were matched as a set. Successive evaluation of the three sets by unreinforced probes showed that the possibility of intermodal generalization gradually increased;the generalization was not found in either direction for the first set, but it proved significant in one direction for the second set and, consequently, in both directions for the third set. These results lead to the conclusion that the chimpanzee’s responses in the two language modes are mutually independent in early acquisition but facilitate one another at a later stage. The implications of these findings for the symbolic function of the naming skill are discussed. This article is based upon the dissertation submitted by the author to the Faculty of Science, Kyoto University, in partial fulfillment of the requirements for the Ph.D degree.