Tests for inhibition after extinction of a conditioned stimulus in the flavour aversion procedure

In four experiments, rats received flavour aversion conditioning followed b y extinction. The flavour was then subjected to retardation and summation t ests. Experiment 1 showed that reacquisition of an extinguished flavour ave rsion was retarded with respect to the performance shown by rats for whom t he flavour was novel. No retardation was found, however, with respect to a control group that had been given non-reinforced pre-exposure to the flavou r. Experiment 2 demonstrated that extinction showed the same sensitivity to the effects of a retention interval as did latent inhibition, consistent w ith the view that the retardation effect was a consequence of the occurrenc e of latent inhibition during extinction. An extinguished stimulus was also found to alleviate the response governed by a separately trained excitor i n a summation test (Experiments 3 and 4), but the size of this effect did n ot exceed that produced by a control stimulus when the procedure used ensur ed an equivalent aversion to the test excitor in the two cases. These resul ts challenge the proposal that extinction can turn a stimulus into a net in hibitor.