Situational relevance: Context as a factor in serial overshadowing of taste aversion learning.

In a serial overshadowing procedure a target stimulus, A, is followed after an interval by a potentially interfering stimulus, B, and this is then followed by an unconditioned stimulus, US. Revusky (1977) proposed that the degree to which B overshadows conditioning of A depends on whether or not the two events take place in the same context. To test this proposal two experiments used a 1-trial long-delay conditioned taste aversion (CTA) procedure; sucrose served as the target taste (A) and dilute hydrochloric acid (HCl) as the overshadowing taste (B), with lithium chloride injection providing the US. In Experiment 1 these tastes were novel; weaker overshadowing by HCl of an aversion to sucrose was found when the two tastes were presented in different contexts. Experiment 2 tested whether the effect of pre-exposure to HCl, thereby rendering it less effective in overshadowing a sucrose aversion, was also context-dependent. In the conditioning session rats again received either context-same or context-different presentations of sucrose and HCl. However, for some rats HCl was pre-exposed in the same context to which it was later presented during conditioning (Consistent), while others were pre-exposed to HCl in a different context to the one in which it was presented during conditioning (Inconsistent). The Inconsistent group produced greater overshadowing than the Consistent group and thus confirmed that the latent inhibition effect was also context dependent. This study supports Revusky's (1977) idea of situational relevance.