Select and reject conditional control on matching to sample and stimulus equivalence.

The purpose of this study was to test Carrigan and Sidman's (1992) hypothesis that the emergence of equivalence relations from the standard matching-to-sample (MTS) procedure is due to the exclusive acquisition of select conditional relations during training. Four groups were compared on tests of the properties of equivalence relations (reflexivity, symmetry, and transitivity/equivalence) and on trials with novel stimuli replacing S+ or S- on these tests: standard MTS training; exclusive-select-relations training; exclusive-reject-relations training; and detached-MTS training, which included training on both select and reject relations. Equivalence emergence occurred more frequently in the detached-MTS group. Those in the standard-MTS group who showed equivalence emergence had test results with novel stimuli that were more similar to those in the detached-MTS group than to those in the exclusive-select group. The results suggest that compliance with the criteria for equivalence relations may mask at least two different processes. The first is pseudoequivalence, which is associated with exclusive select control. The second is the authentic formation of equivalence classes, which depends on joint select and reject control. The standard-MTS procedure seems to more frequently promote the second process.