Acquired equivalence and distinctiveness of cues using a sensory-preconditioning procedure

In Experiment 1 rats were presented with two flavours, A and B, that were accompanied either by a third common flavour, X, or by two different flavours, X and Y, respectively. An aversion was then established to A, and the extent to which this aversion generalized to B was measured. Stimulus generalization was found to be more marked when A and B had both been presented with the same flavour, X, during pre-exposure than when A and B had been presented with X and Y. In Experiment 2 three target flavours, A, B, and C, were initially presented. In one pre-exposure condition presentations of A and B were accompanied by X, and C was presented alone; in a second condition A and B were presented in isolation, and C was accompanied by X. After an aversion had been established to A, half of the animals in each of the pre-exposure conditions were tested with B, and the remainder were tested with C. In both of the pre-exposure conditions the generalized aversion was more substantial to B than to C. An analysis of these results in terms of the mechanisms that have been supposed to underlie sensory preconditioning is presented.