Effects of Outcome Devaluation on the Performance of a Heterogeneous Instrumental Chain

Abstract

Two experiments investigated the effects of outcome devaluation induced by conditioned taste aversion on the performance of the components of a heterogeneous chain of instrumental actions. In Experiment 1, thirsty rats were trained to perform two actions, R1 and R2, i.e., chain pulling and lever pressing counterbalanced, in sequence to gain access to a sucrose outcome in a single session; i.e., R1→R2→O. Immediately after this session or after a delay the rats were injected with lithium chloride and given an extinction test on the two actions the next day. Although the immediate and delayed groups did not differ in the incidence of R1 on test, the immediate group reduced their performance of R2 relative to the delayed group. Experiment 2 assessed the effect of incentive learning after outcome devaluation. All rats were given an injection of lithium chloride immediately after training on the heterogeneous chain for sucrose reward after which half of the rats were reexposed to the sucrose whereas the remainder were reexposed to water prior to the extinction test. Although reexposure had no effect on the test performance of the R2 component in the chain, it significantly reduced performance of R1. These data are consistent with previous claims that responses proximal to outcome delivery are influenced by a Pavlovian incentive process whereas those more distal are controlled by the experienced incentive value of the outcome; i.e., by an instrumental incentive process.