FORMATION OF GENERALIZED EQUIVALENCE CLASSES

A category can contain either an infinite or limited number of stimuli. Categories with an infinite number of stimuli have been called open-ended; they contain stimuli that are physically similar. Categories with a-limited number of stimuli include functional classes and equivalence classes; they contain stimuli that are physically disparate. The processes of equivalence class formation and primary generalization acting in combination yield a category containing stimuli that are physically similar as well as those that are physically disparate. Such a category is called a generalized equivalence class. A response trained to one member of such a class transfers to all remaining members of that class, yielding a generalized functional class. The extension of equivalence classes through generalization is predicted from primary generalization gradients obtained before class formation. Generalized equivalence classes and generalized functional classes bring together the study of stimulus equivalence and open-ended categories. They also provide a plausible account of the establishment of complex categories observed in natural settings.