Overshadowing and associability change.

Abstract

Three appetitive Pavlovian conditioning experiments with rats examined the associability of stimuli A and B that had a history of compound conditioning (ABϩ), relative to stimuli X and Y that had a history of conditioning in isolation (Xϩ, Yϩ). Following this training, Experiment 1 revealed that conditioned responding was higher to X and Y than to A and B (overshadowing). In a subsequent AYϩ, AXϪ, BYϪ test discrimination, the AY/BY discrimination was solved more readily than the AY/AX discrimination. In Experiment 2, following ABϩ, Xϩ, Yϩ training, A and Y were presented as a compound and signaled the availability of reinforcement upon the performance of an instrumental response. Test trials in which A and Y were presented alone, and in extinction, revealed that A acquired greater control of instrumental responding than Y. Experiment 3 revealed that following ABϩ, Xϩ, Yϩ training, A and B served as more effective discriminative stimuli for instrumental responding than X and Y. Overall, these results imply that the associability of stimuli conditioned in compound is higher than stimuli conditioned in isolation. These results are discussed in terms of attentional theories of associative learning.

Overshadowing and associability change: Examining the contribution of differential stimulus exposure

“…This pattern of test discrimination is identical to that reported in Jones and Haselgrove (2011), and therefore supports the possibility that the compound exposure to A and B, as compared to the elemental exposure to X and Y, may have contributed to their results. The results of Experiment 1 are also consistent with the results of a latent inhibition experiment reported by Honey and Hall (1988).…”

“…This result was again inconsistent with the idea that attention was less to A than to Y; if this were the case, the more salient Y should have taken better control over instrumental responding on R1 than had the less salient A. Jones and Haselgrove (2011) suggested that their results, while incompatible with Mackintosh's (1975) original model of attention and learning, could be explained by a more complex hybrid model proposed by Pearce and Mackintosh (2010). To avoid undue repetition, the details of this explanation will not be described fully here, but, in brief, the analysis is based on the idea that an algorithm that employs a total prediction error (Rescorla & Wagner, 1972) is used to update associative connections between the CS and the US and that an algorithm that employs an individual prediction error between each CS and the US (Bush & Mosteller, 1951) is used to update attention to a CS.…”

“…The results of Jones and Haselgrove's (2011) Experiment 2 expanded upon the results of their Experiment 1: Following identical training in Stage 1 (X+, Y+, AB+), rats were presented with an AY compound. Instrumental responses made on one lever (Response 1: R1) during AY led to delivery of the US, but instrumental responses on another lever (Response 2: R2) did not.…”

“…More recently, a series of experiments reported by Jones and Haselgrove (2011) tested the predictions of Mackintosh's (1975) analysis of overshadowing. They examined whether a cue that had a history of overshadowing training would subsequently be less successful in taking control of conditioned behavior than was a cue with a history of being conditioned in isolation.…”

“…However, an unsatisfactory feature of the experiments described by Jones and Haselgrove (2011), and indeed of most studies of overshadowing (but see Dwyer, Haselgrove, & Jones, 2011), was the control stimuli against which the overshadowed stimuli were compared. Unlike the overshadowed stimuli (A and B), the control stimuli (X and Y) were presented in isolation throughout training.…”