Use of exclusion by a chimpanzee (Pan troglodytes) during speech perception and auditory-visual matching-to-sample

Abstract

An adult female chimpanzee showed responding through use of exclusion in an auditory to visual matching-to-sample procedure. The chimpanzee had previously learned to associate specific visuographic symbols called lexigrams with real world referents and the spoken English words and photographs for those referents. On some trials, an unknown spoken English word was presented as the sample, and the match choices could consist of photographs or lexigrams that already were associated with known English words as well as unknown lexigrams or photos of objects without associated lexigrams. The chimpanzee reliably avoided choosing known comparisons for these unknown samples, instead relying on exclusion to choose comparisons that were of unknown lexigrams or photographs of items without associated lexigram symbols.

Figure 1

A. Panzee’s performance when presented with lexigram comparison stimuli and an undefined sample stimulus. Bars present her percentage correct and the expected performance level if exclusion was used. The lines indicate the percentage of incorrect trials that involved selection of an undefined comparison stimulus by Panzee and the percentage expected by chance. The thick horizontal line represents the true chance level (25%). B. Panzee’s performance when presented with photograph comparison stimuli and an undefined sample stimulus, shown in the same way as in A.