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Equivalence formation, expansion, and reversal were investigated as a result of arbitrary matching associated with specific reinforcers. Four 4- and 5-year-old normal children were taught identity matching with stimuli, A, B, C, and D, and stimulus specific reinforcement. Then the children were taught two conditional discriminations AB and BC. All subjects showed formation of the ABC stimulus classes; one subject, however, did not show expansion to ABCD classes. This subject was taught to name the D stimuli, he then demonstrated the expanded class. Next, 2 subjects who showed expanded classes were taught identity matching with the reinforcers reversed for the D stimuli. In tests that followed, their matching responses remained consistent with the original equivalence classes. These subjects were then taught to reverse the names for the D stimuli. As a result, the children reversed the classes. The results suggest that class expansion and subsequent reformation of classes may be facilitated when stimulus within each class controls a common naming response.