Matching-to-sample procedures and the development of equivalence relations: The role of naming

Two normal children and four retarded youths were taught auditory-visual and visual-visual conditional discriminations and were then tested to determine whether the conditional relations were also equivalence relations. All subjects showed that conditionally related sample and comparison stimuli had become equivalent; the conditional discriminations generated two sets of three-member classes, one set containing both auditory and visual stimuli and the other containing only visual stimuli. In the auditory-visual classes, two of the retarded subjects failed to apply the name of the auditory stimulus to each visual stimulus in the same class; in the visual classes, all but one normal subject failed to apply a consistent label to all stimuli in a class. The formation of classes of equivalent stimuli does not, therefore, require that common names be applied to each member of a class. Although common naming responses were not necessary for equivalence, relations denoting symmetry and transitivity in the original conditional discriminations were shown to be prerequisites, as is demanded by the definition of equivalence.