Motivational interactions: The Role of Inhibition in Pavlovian Aversive to Appetitive Transfer
The nature of motivational interactions between appetitive and aversive response systems was assessed in four Pavlovian transfer studies where the two conditional responses are peripherally independent. The theory of reciprocal inhibition postulates that excitatory aversive conditioning would inhibit appetitive conditioning. Furthermore, inhibitory aversive conditioning would enhance appetitive conditioning. According to recent formulations of reciprocal inhibition, several transfer effects are predicted on the basis of results found within a single motivational system. Some of these were tested here for Pavlovian motivational transfer.
In each transfer study, four aversive pretraining conditions were used. Excitatory aversive conditioning was conducted by forward pairings of the tone CS with shock. Inhibitory aversive pretraining was conducted by backward pairings, where the shock preceded the tone. In addition, two control conditions were included: a random control, where the tone CS and shock were presented in an uncorrelated manner; and a naive control condition, where no tones or shocks were presented. The four transfer studies differed only in their treatment in the transfer phase.
Experiment 1 transferred aversive pretraining onto an aversive conditional inhibition discrimination to the pretrained tone. This transfer design is sensitive to inhibitory pretraining and was used to demonstrate clearly that backward pretraining effectively produces an inhibitory aversive CS and that random pretraining does not. The results showed that backward pretraining with the shock and tone enhanced the acquisition of a conditional inhibition discrimination to the backward tone CS. Random pretraining, on the other hand, interferred with the acquisition of conditional inhibition to the random tone CS.
Experimental 2 transferred aversive pretraining onto the simple acquisition of appetitive responding to the tone CS. Excitatory aversive pretraining profoundly retarded acquisition to the tone CS. Inhibitory aversive pretraining enhanced appetitive responding to the tone CS compared to the naive control condition, but not compared to the random control condition which also showed enhanced acquisition compared to the naive control condition. With the exception of performance in the random control condition, Experiment 2 confirmed the predictions of reciprocal inhibition.
Experimental 3 transferred aversive pretraining onto the acquisition of an appetitive conditional inhibition discrimination to the tone CS. The excitatory aversive tone suppressed appetitive responding from the outset of discrimination training. Although the inhibitory aversive and random control conditions enhanced responding on negative trials initially, this enhancement was short-lived compared to the naive control condition. The results of Experiment 3 confirmed the inhibitory nature of excitatory aversive transfer to the appetitive system, but are inconclusive with respect to the predicted facilitative nature of inhibitory aversive transfer for the appetitive system.
Experiment 4 transferred aversive pretraining onto compound appetitive conditioning. Excitatory aversive pretraining suppressed responding during compound acquisition, but showed enhanced responding to the previously neutral light CS ("superconditioning") compared to naive control condition which received appetitive conditioning to the light alone. Inhibitory aversive pretraining enhanced responding during compound conditioning compared to the naive control conditions but not more than the random control condition. Both the inhibitory aversive and random control conditions responded more to the light CS than the naive control condition, but were not different from the naive control condition which received light alone acquisition. This apparent reduction in overshadowing is inconsistent with the predictions of reciprocal inhibition for inhibitory aversive transfer.
Taken together, the results suggest that aversive excitation is inhibitory, but aversive inhibition is not facilitative, for the appetitive conditioning system. A model is proposed which incorporates this asymmetry in motivational interactions. In addition, analysis of control group performance suggests that greater attention be paid to contextual conditioning and pseudoconditioning in assessing motivational interactions.