Chimpanzees are well known to be our closest non-human relatives, but the surprising extent to which they share cognitive abilities with human beings is still being discovered. Drs. Boysen and Berntson are investigating the numerical competence of chimpanzees. Their studies should contribute to our understanding of the similarities and differences in cognitive capabilities across species and toward clarifying those processes that may support numerical skills in non-human primates. Besides these contributions to basic scientific knowledge, these studies may yield sharper tests for and understanding of numerical competence in children and, more generally, provide a better understanding of non-verbal intelligence. Thus, the present project may provide insights into the cognitive abilities of language-impaired or otherwise developmentally-challenged children. Experiments will examine the manipulation of numerical symbols, the emergence of counting skills, and the representational nature of number symbols. Training methods previously developed will be extended to increase the range and functional significance of number use by three young-adult chimpanzees, and to examine features of summation and subtraction using arrays containing both symbols and objects. The emergence of counting skills will also be examined in an adult and an infant chimpanzee, including an analysis of ability to recognize the position within the series from 1 to 7 of two quantities (3, 6) that have not previously been paired with arrays of objects. The contribution of abstract symbol use will be further examined in a study of food sharing that employs Arabic numerals and arrays of objects in a social, cooperative context. A final study will investigate the chimpanzees' formation of equivalence sets among categories of numerical stimuli.
