Stimulus Classes Formation in Concurrent Discriminations in Rats as a Function of Overtraining

Abstract

The present two experiments conducted a limited parametric study of the overtraining variable using a whole-partial reversal procedure in rats. Rats received two concurrent two-choice discriminations (Experiment 1) , two concurrent go-no go successive discriminations (Experiment 2), and then received reversal training under a given condition of a whole reversal or a partial reversal either immediately after criterion training , following 2, 10, or 20 days of overtraining in Experiments 1 and 2. In Experiment 1, after 20 days of overtraining, a whole reversal , in which both discrimination tasks were reversed , produced more rapid reversal than a partial condition , in which one of the two discriminations was reversed whereas the other was maintained as in original learning. Conversely, after 2 days of overtraining rats in the partial condition reversed faster than did those in the whole condition. Experiment 2 essentially replicated results of Experiment 1. Experiments 1 and 2 show that a stimulus function transfer and stimulus substitutability, respectively, are most clearly evident after 20 days of overtraining. These results indicate that additional prereversal training (i.e., overtraining) is an obvious operational precondition for stimulus classes formation in simple concurrent discriminations in rats.There are two separate definitions of a stimulus class: The first one pertains to functional equivalence, and the second pertains to the control of a specific response by one member of the stimulus class. Goldiamond (1962) argues that both are necessary for a set of stimuli to be considered a stimulus class. This argument is a very important and even fundamental issue in behavior analysis, and one that has received far too little experimental attention.Nakagawa (1986, 1992), using a whole-partial reversal procedure which compared rats' performance on whole reversal sessions (both stimulus pairs reversed, from A+C-, 8+0-to A-C+ , 8-0+ for example) with that on partial reversal sessions (only one pair reversed, from A-C+, 8-0+ to A+C-, 8-0+ for example) , reported that rats could form stimulus classes during overtraining in concurrent discriminations. In Nakagawa's experiments , rats were trained to criterion or overt rained on two Requests for reprints should be sent to Esho Nakagawa,

A Factor Affecting Stimulus Classes Formation in Concurrent Discriminations in Rats

“…, 1992). The other is stimulus associations on a basis of the same response following the same consequence (Nakagawa, 1978(Nakagawa, , 1986(Nakagawa, , 1992(Nakagawa, , 1993(Nakagawa, , 1998Delius et aI., 1995). However, st imulus assoc iation mechanisms postulated by Nakagawa (1978Nakagawa ( , 1986Nakagawa ( , 1992Nakagawa ( , 1993Nakagawa ( , 1998 and Delius et al (1995) are not necessarily in conflict with stimulus association process based on downright reinforcement concordance (Edwards et aI., 1982;Hall et aI., 1993;Urcuioli et aI., 1989;Zentall, Sherburne, et aI., 1992, Zentall, Steirn, et aI.…”

“…Group W learned their reversal faster than Group P after overtraining , but not after criterion training. These results indicate that the same response is a factor affecting stimulus classes formation in rats.There are two main views on the formation mechanism of stimulus classes: The one is categorization processes based on simple similarity between stimuli (Bhatt & Wasserman, 1989;Fersen & Lea, 1990; Vaughan & Herrstein, 1987), the other is stimulus associations on the basis of reinforcement concordance (Deli us, Ameling, Lea, & Staddon, 1995;Edwards, Jagielo, Zentall, & Hogan, 1982;Nakagawa, 1986Nakagawa, , 1992Nakagawa, , 1998 Urcuioli, Zentall, Jackson, Smith, & Steirn, 1989, 1998. However, it is important to note that such stimulus associations mechanism as postulated in Nakagawa (1986, 1992, 1998) and Delius et al (1995) is not necessarily in conflict with categorization processes based on simple similarity between stimuli.…”

“…Using a whole-partial reversal procedure which compared rats' performances on whole reversal sessions (both stimulus pairs reversed, from A+C-, B+O-to A-C+, B-O+ for example) with those on partial reversal sessions (only one pair reversed, from A-C+, B-O+ to A+C-, B-0+ for example), Nakagawa (1978Nakagawa ( , 1986Nakagawa ( , 1992Nakagawa ( , 1998 has shown that rats form stimulus classes between the discriminative stimuli on the basis of the same response during overtraining in concurrent discriminations. In Nakagawa's experiments, rats were trained to criterion or overtrained on two concurrent discriminations (A+C-, B+O-for example) in Phase 1 training in both a simultaneous (Nakagawa, 1986(Nakagawa, , 1998) and a go-no go successive concurrent discriminations (Nakagawa, 1992(Nakagawa, , 1998.…”

“…In Nakagawa's experiments, rats were trained to criterion or overtrained on two concurrent discriminations (A+C-, B+O-for example) in Phase 1 training in both a simultaneous (Nakagawa, 1986(Nakagawa, , 1998) and a go-no go successive concurrent discriminations (Nakagawa, 1992(Nakagawa, , 1998. After completing Phase 1 training, rats received either partial reversal (only one pair reversed from A+C-, B+O-to either A-C+, B+O-or A+C-, B-O+ for example) or whole reversal (both stimulus pairs reversed , from A+C-, B+O-to A-C+, B-O+ for example).…”

Acquired Equivalence of Discriminative Stimuli Following Two Concurrent Discrimination Learning Tasks as a Function of Overtraining in Rats

“…This finding makes it clear that pigeons form stimulus classes. Nakagawa (1978Nakagawa ( , 1986Nakagawa ( , 1992Nakagawa ( , 1998, using a whole-partial reversal procedure which compared rats' performance on whole reversal sessions (both stimulus pairs reversed, from A+C-, 8+0-to A-C+, 8-0+ for example) with rats' performance on partial reversal sessions (only one pair reversed , from A-C+, 8-0+ to A+C-, 8-0+ for example) , reported that rats could form stimulus classes. In a series of Nakagawa's experiments, rats were trained to criterion or overtrained on two concurrent discriminations (A+C-, 8+0-) in both simultaneous (1986,1998) and go-no go successive concurrent discriminations (1992,1998) in Phase 1 training .…”