It is safe to say that all organisms have discriminative capacities that are never fully developed because their environments never provide differential consequences of selective behavior in the presence of minimally different stimuli. The cultured palate of the wine taster, the discerning nostrils of the perfumer, the critical ear of the conductor, the sensitive fingers of the safecracker, and the educated eyes of the painter are familiar illustrations of discriminative capacities that remain relatively untapped in most human beings.