A dissociation between one-trial overshadowing and the effect of a distractor on habituation

Rats drank a novel vinegar flavour and were subsequently tested either for habituation of neophobia to vinegar or for the conditioning of an aversion to vinegar when it was followed 4 hr later by an injection of lithium chloride. If they drank a sucrose distractor immediately after their first vinegar trial, habituation of neophobia was disrupted but conditioning was not. Sucrose consumed 3.5 hr after the initial vinegar trial, on the other hand, had less of an effect on habituation, but did disrupt conditioning. An incidental finding, replicated in two subsequent experiments, was that the immediate sucrose distractor had no effect on habituation when animals were tested 48 hr after their initial habituation trial. We interpret these results to suggest that distractors affect habituation by a process of generalization decrement but overshadow conditioning through a process of associative competition.