Simultaneous discrimination learning: Stimulus interactions

Abstract

Stimulus Similarity EffectsThe degree of physical similarity between the S1 and the S during the acquisition of a discrimination has played an important role in theories of discrimination learning (see, e.g., Lawrence, 1955;Logan, 1966;Spence, 1937). By making certain assumptions-(1) that the excitatory strength of the S1 is greater than the inhibitory strength of the S ; (2) that the shape of the generalization gradient is concave downward; and (3) that the net effect can be represented by the algebraic summation of the two (i.e., excitation minus inhibition)-Spence was able to 311Copyright 2001 Psychonomic Society, Inc.Preparation of this article was supported by Grants MH55118 and MH59194 from the National Institute of Mental Health to T.R.Z. We thank Lou M. Sherburne, Brigette R. Dorrance, Janice E. Weaver, Daren H. Kaiser, and Andrea M. Lonon for their contribution to the research described here and William Timberlake for his encouragement to prepare this article. Correspondence concerning this article should be sent to T. R. Zentall, Department of Psychology, University of Kentucky, Lexington, KY 40506 (e-mail: zentall@pop.uky.edu). Simultaneous discrimination learning:Stimulus interactions THOMAS R. ZENTALL and TRICIA S. CLEMENT University of Kentucky, Lexington, KentuckyAlthough considerable attention has been given to interactions between events serving as the positive (S1) and negative (S ) stimuli in successive discriminations, there has been little study of similar interactions in simultaneous discriminations. We propose that in a simultaneous discrimination, given what is typically relatively little experience with the consequences of responding to the S , some of the value of the S1 transfers to the S with which it was paired. Furthermore, the mechanisms responsible for this transfer of value appear to be the higher order Pavlovian association between the S and the S1, as well as within-event associations between them. Although in typical simultaneous discriminations, negative value does not appear to transfer from the S to the S1, when adequate experience is provided with the S , contrast typically develops, reducing the value of the S (negative contrast) and enhancing the value of the S1 (positive contrast). This model of stimulus interactions has implications not only for simple simultaneous discrimination learning, but also for research using combinations of discriminations (e.g., transitive inference in animals and humans). This model may also have implications for a number of human social psychological phenomena.

Contrast and the justification of effort

“…Although the participants did rank the high-effort SϪ stimuli as better than the low-effort SϪ stimuli, when given a choice between high-effort SϪ stimuli and low-effort SϪ stimuli, no significant difference was found. Clement et al attributed the preference for the SϪ stimulus that followed greater effort to the transfer of value from the Sϩ to the SϪ stimuli in each discrimination (see Zentall & Clement, 2001). But other research has found no evidence for a preference for the SϪ stimulus that followed greater effort (Clement & Zentall, 2002;DiGian et al, 2004;Friedrich et al, in press).…”

Cognitive dissonance in children: Justification of effort or contrast?

“…In research with pigeons, we have sometimes found a preference for the S stimulus similar to the preference for the S stimulus that followed the less-preferred event in training (Clement et al, 2000), but in several other experiments a preference for the S stimulus has not been found (DiGian et al, 2004;Friedrich et al, 2005). When we have sometimes found such an S preference, we have explained it in terms of value that may transfer from an S to an S in a simultaneous discrimination (Zentall & Clement, 2001). However, we have also suggested that the reason the S effect is often not found is that reliable value transfer effects occur primarily when the S stimuli themselves have a greater difference in absolute value (e.g., differential probability of reinforcement) than they do in the present design.…”

Value transfer contributes to ambiguous-cue discrimination learning

“…Nonetheless, recent analyses of discrimination learning suggest that other associative factors may also contribute to performance. Specifically, Zentall and his associates (Zentall & Clement, 2001;Sherburne, 1994) andvon Fersen et al (1991) have proposed that the S in a simultaneous discrimination acquires some positive or excitatory value from the S which it accompanies. Stated otherwise, some of the value that directly accrues to an S via reinforced responding to it transfers to the S with which it is presented.…”