ABSTRACT
One type of concept learning in animals is inferred when the animal's behavior suggests that it has learned some rudimentary rule involving same/different judgments. That is, an animal's behavior is controlled to some extent by conditional relationships among stimuli rather than by their absolute values. R. J. Herrnstein and D. H. Loveland wrote that the pigeon will form a complex concept when placed in a situation that demands one. When pigeons serve as the subjects, the standard three key matching-to-sample procedure (MTS) employing three hues or forms usually fails to produce convincing evidence of concept learning when a fourth sample is introduced. The multiple MTS procedure with a sample ratio of 3 and sequential presentation of the comparison stimuli produces facilitated matching performance for several reasons.
