Problem solution by monkeys following bilateral removal of the prefrontal areas: VI. Performance on tests requiring contradictory reactions to similar and to identical stimuli.

Abstract

5 normal monkeys and 5 monkeys with bilateral destruction of the prefrontal areas were given a series of 200 tests on problems requiring contradictory reactions to similar or identical stimuli. The normal monkeys were superior to the operated animals and the differences were significant for all groups of tests. The performance of the most proficient operated animal was inferior to that of the least proficient normal animal. The inferior performance of the operated monkeys was interpreted as resulting from impairment of the ability to relinquish previously acquired, interfering reaction patterns.