Symbolic cross-modal transfer in two species of chimpanzees

Abstract

2 common chimpanzees and 1 pygmy chimpanzee, all of whom were proficient lexigram symbol users, were tested on symbolic cross-modal tasks. Previous cross-modal work with nonhuman primates has been limited to nonsymbolic matching tasks. None of these chimpanzees received any advance training on cross-modal tasks prior to the testing reported here. The common chimpanzees, Sherman and Austin, were tested on visual to haptic, visual-symbolic to haptic, haptic to visual-symbolic, and olfactory to visual-symbolic matching tasks. The pygmy chimpanzee, Kanzi, was tested on auditory-symbolic to pictorial and auditory-symbolic to visual-symbolic matching tasks. All subjects were able to match stimuli across the tested dimensions with no training. These results indicate that chimpanzees who have received symbol training can perform symbolic cross-modal tasks similar to those that are typically used with human subjects. These tasks require not only cross-modal associations but also the transformation of information from symbolic to representational modes.