Generalization Gradients of Excitation and Inhibition: Long-Term Memory for Dimensional Control and Curious Inversions During Repeated Tests With Reinforcement

The analysis of operant generalization gradients along dimensions of reinforcement-associated (excitatory, S⁺) and extinction-associated (inhibitory, S⁻) stimuli was a major research area for students of animal learning during the 1960s and early 1970s (see Hearst, Besley, & Farthing, 1970; Honig & Urcuioli, 1981; Mackintosh, 1974, 1977; Mostofsky, 1965; Rilling, 1977; Terrace, 1966). Historically, interest in this topic was fostered by the results and theories of pioneers like Hull, Kohler, Lashley, Miller, Pavlov, Skinner, and Spence, who explored aspects of the relationships between stimulus generalization and such phenomena as discrimination learning, selective attention, induction-contrast, conflict, and transposition. Riley's (1968) book on Discrimination Learning provided an important summary and evaluation of classic work and enduring controversies in the field and suggested useful directions for future experimentation and theorizing, many of which were later examined.