29. Object and Color Naming in Chimpanzees (Pan troglodytes)

and other artificial visual languages were taught to chimpanzees and a gorilla.1 6 Controversies emerged among experimental psycholo-gists, linguists and others, but currently there is no consensus on what apes really learn and how.7 ~ Savage-Rumbaugh et al.8~,9) in-vestigated the initial acquisition of symbolic skills. They failed to train chimpanzees to name colors or objects by depressing keys with geometric symbols. The chimpanzees learned competently when they asked for food or tools by pressing symbol keys, and the importance of request training in developing symbolic use of lexigrams was emphasized. Up to now, to our knowledge, experimental evidence has not been available demonstrating that a chimpanzee can name items without previous training to request the items. Our chimpanzees learned lexigram names of objects and/or their colors through train-ing for which naming responses were reinforced with a common food reward rather than by giving the named item. Three nondeprived young wild-born chimpanzees, Ai (female), Akira (male), and Mani (female), were the subjects. When train-ing started in April, 1978, their ages were estimated to be about two years. They were carried into the training room (190 x 220 x 180 cm) from their home cage and left alone there for daily sessions of about one hour to earn food rewards. A piece of apple or raisin was delivered after 1-5 consecutive correct responses. Sessions were controlled by a mini-computer, PDP11/V03. After an initial 3-4 month adaptation period to laboratory con-ditions, 8-9 months were spent in extensive training in matching-to-sample tasks, first with colors and then with geometric figures. In the initial task, the color sample (53x38 mm) was displayed on a panel, and pressing a key of the same color was rewarded. The three chimpanzees learned five-color matching in 29-34 sessions. Then the color stimuli were replaced by the geometric figures. Eac