Emergence of assimilation or contrast effects in backward evaluative conditioning does not depend on US offset predictability

Abstract

Backward evaluative conditioning has been shown to result in assimilative effects where backward conditional stimuli (CS) acquire the valence of the unconditional stimulus (US) or in contrast effects where backward CSs acquire valence opposite to the US. The current experiments were designed to assess whether the nature of evaluative backward conditioning varies as a function of US offset predictability, manipulated by varying US duration (fixed vs. variable), US-CS overlap (overlap vs. no overlap), and the presence of a forward conditioning CS. Experiment 1 employed backward conditioning only (USPleasant-CS1; USUnpleasant-CS2) whereas Experiment 2 employed concurrent forward and backward conditioning (CS3-USPleasant-CS1; CS4-USUnpleasant-CS2). Backward CS assimilation effects emerged in both experiments and did not differ as a function of US duration. Presence of a forward CS reduced backward conditioning, in particular in the no US-CS overlap condition. These findings provide no support for the notion that the nature of backward CS evaluations varies as a function of US offset predictability and indicate that concurrent forward conditioning can modulate the extent of backward conditioning and the effect of US-CS overlap.