Sameness-difference matching from sample by chimpanzees

Abstract

Two adult chimpanzees were trained on a sameness-difference matching from sample task with five levels of difficulty, ranging from a simple form of matching from sample in Phase 1, to a fully generalized form of matching from sample in Phase 5. The development of hypotheses by both subjects during each phase was analyzed. In Phase 1, both animals initially showed considerable position and random responding, both of which decreased as correct and 2/3-correct responding increased. In all later phases, however, position responding was minimal, random responding characterized the beginning of each phase, and correct responding characterized the end of each phase. © 1975, The Psychonomic Society, Inc.. All rights reserved.