Comparison of ape and monkey modes of problem solution.

A series of 4 experiments investigated the mode (hypothesis or stimulus-response association) of problem solution by various primate species on a modified discrimination-reversal task. The procedure in Exp I was identical to that of an experiment by D. M. Rumbaugh (see record 1972-02524-001) in which Ss were first trained to criterion on a junk-object discrimination problem (A+B–). Following 1 standard reversal trial (A-B+), in 2 of the 3 postreversal conditions, a novel stimulus replaced either the initially correct or the initially incorrect stimulus, which thereby obviated the need either for extinction to A or for counterconditioning to B. As did the talapoin monkeys in the Rumbaugh study, rhesus and stumptailed monkeys solved the problem associationally. As a direct test of hypothesis usage by apes and monkeys, Exps II and III manipulated the level of ape and monkey prereversal problem mastery by varying the prereversal criterion. Once their postreversal performance had stabilized, both orangutans and macaques evidenced hypothesis-based responding, but the ape and monkey response strategies were based on qualitatively different relational cues. Exp IV demonstrated that the macaques in Exp I showed associational learning exclusively only because the amount of exposure to the task was insufficient to foster hypothesis usage. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)