A modified discrimination-reversal (DR) task was used to determine whether qualitative differences exist in the learning processes of gorillas, gibbons, and talapoins. Whereas the talapoins were presumed to be primarily stimulus-response associational learners, it was assumed that the first two groups by virtue of their relatively advanced cortical development might manifest some more abstract learning process. Subsequent to criterional training on each object-quality discrimination problem, a first DR trial was given in accordance with convention (A+ became -; B-became +). In two of the DR conditions a new stimulus was then substituted for either A or B, to obviate either extinction to A or counterconditioning to B. Apart from the gibbons being particularly responsive to the novelty of the new stimulus, the results were in accord with predictions.

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