No abstract

Chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta) selected either Arabic numerals or colored squares on a computer monitor in a learned sequence. On shift trials, the locations of 2 stimuli were interchanged at some point. More errors were made when this interchange occurred for the next 2 stimuli to be selected than when the interchange was for stimuli later in the sequence. On mask trials, all remaining stimuli were occluded after the 1st selection. Performance exceeded chance levels for only 1 selection after these masks were applied. There was no difference in performance for either stimulus type (numerals or colors). The data indicated that the animals planned only the next selection during these computerized tasks as opposed to planning the entire response sequence.

The field of ape language has been in turmoil since the publication of Terrace's (1979) work with. Nim, a chimpanzee. Terrace's findings regarding the linguistic competencies of apes contrasted sharply with those put forth earlier by Gardner and Gardner (1971). We discuss these and other ape-language projects and contrast the preverbal communicative skills of chimpanzees with those of human children in order to, determine the cognitive competencies that chimpanzees bring to the task of language acquisition. We conclude that children enter the one-word stage with a gestural-referential complex of abilities that permits them to engage quickly in a process of mutual vocal reference and that predisposes them to view words as behaviors that stand for or replace objects. Chimpanzees do not seem to develop spontaneously a similar gestural-referential complex of communicative skills, and therefore they do not readily comprehend the act of reference that the teacher is engaged in while pointing to and naming objects. Thus, although chimpanzees imitate the symbol, they do not readily interpret the symbol as a referent in the manner that a human child does. This distinction between child and chimpanzee has not been made previously, and it is suggested that the lack of such a distinction has resulted in overinterpretations of apes' linguistic abilities. Data are presented that demonstrate that the gestural-referential complex can be developed, with training, in the chimpanzee and that, consequently, naming with reference does appear. This is demonstrated in controlled tests with two chimpanzees. A review of the training that preceded the emergence of referential function in these chimpanzees suggests that symbolization is not a unitary skill but rather a combination of diverse productive and receptive skills. This view is supported by human data. Contrasting Views of Indication in Apesdifference between the use of language by apes ", , _ , , and children lies in the fact that apes do not Terrace and Rumbaugh seem motivated to use their words in any sort Terrace, Pettito, Sanders, and Bever (1979) of declarative or indicative sense. That is, they have asserted that a profound and important do not typically use symbols to announce to others what they are about to do or to draw the attention of others to objects or events.

In this experiment, a chimpanzee's (Pan troglodytes) long-term retention was examined. The chimpanzee, Lana, was trained to use lexigrams (geometric symbols representing linguistic units) for foods, colors, and objects when she was 2 years of age. At the age of 27, her recognition of three sets of lexigrams was examined. One of these sets (long term lexigrams) included five object lexigrams, one color lexigram, and one food lexigram, none of which had been seen by Lana for more than 20 years. The second set (different-referent lexigrams) contained lexigrams that are still present on current lexigram keyboards, but had been assigned new referents. The third set (same-referent lexigrams) contained lexigrams that had been kept on the keyboards Lana had used and that had retained the same referents. A food, a colored square, or an object was presented, and Lana had to select, by using ajoystick, a lexigram on a computer screen. Lana chose the correct lexigram at a level significantly greater than chance for five of the seven lexigrarns that she had not seen for more than 20 years.Human subjects can retain information for variable lengths oftime. They can retain, over a period of months and even years, course schedules and word lists

For persons with severe retardation, learning to communicate symbolically is a complex long-term process requiring the coordination of many components to succeed. Three of four institutionalized adolescents and young adults with severe retardation who participated in this study learned to use lexigrams to request foods and, subsequently, objects. Although their request skill did not initially generalize to labeling and to comprehension tasks, additional request experience with lexigrams resulted in consistent improvement in performance in both tasks. The emergence of subject-initiated lexigram communications and the facilitation of spoken language comprehension and/or production were also observed.