Effects of outcome devaluation on instrumental behaviors in a discriminated heterogeneous chain

Abstract

Operant behavior often takes place in a sequence, or chain, of linked responses that lead to a reinforcer. We have recently studied rats performing a discriminated heterogeneous behavior chain that involves the presentation of a discriminative stimulus (e.g., a panel light) to set the occasion for a procurement behavior (e.g., a lever press) that leads to a second stimulus (e.g., a second panel light) that indicates that a consumption response (e.g., a chain pull) will be reinforced. The present study assessed the role played by a representation of the reinforcer in controlling the performance of the responses in this chain. After acquisition of the chain, rats received a reinforcer devaluation treatment in the form of repeated paired, or unpaired, presentations of the food-pellet outcome and lithium-chloride illness. Once paired rats came to reject the pellets, half the animals in each group were tested on procurement, and the other half were tested on consumption. Neither response was affected by the outcome devaluation treatment, although entries into the food cup were suppressed. Combined with other results, the findings suggest that the "goal" for goal-directed procurement responding in a discriminated heterogeneous chain may be the consumption response rather than the primary reinforcer. (PsycINFO Database Record

Figure 1

Test responding. a.) Procurement (R1) and b.) consumption (R2) response rates in each 4-trial block for groups tested with procurement (S1) and consumption (S2) stimuli, respectively. c.) Consumption (R2) response rates in groups tested with S1 and d.) procurement (R1) response rates in groups tested with S2 in each 4-trial block. e.) and f.) Food cup entry rates in each 4-trial block for groups tested with S1 and S2, respectively. Error bars are the standard error of the mean and only appropriate for between group comparisons.

Figure 2

Reacquisition test. a.) Number of pellets earned and number eaten in the chain reacquisition session. R2 (b.) and R1 (c.) response rate elevation scores across 5-trial blocks of the reacquisition session. Error bars are the standard error of the mean and only appropriate for between group comparisons.