Dissociation between the Espinet and perceptual learning effects in flavour aversion conditioning.

In three experiments rats were given pre-exposure to two compound flavours, AX and BX, the two compounds being presented for some subjects on alternate trials (the intermixed schedule) and, for others, in separate blocks of trials (the blocked schedule). After aversion conditioning with A (in Experiments 1 and 2), the inhibitory properties of B were tested using both retardation (Experiment 1) and summation tests (Experiment 2). The results failed to support the proposal [Anim. Learn. Behav. 23 (1995) 361] that B should acquire inhibitory properties in the intermixed condition (the "Espinet effect"). Experiment 3 demonstrated that generalisation to BX after conditioning with AX was attenuated by intermixed pre-exposure (a perceptual learning effect). This pattern of results challenges the hypothesis that inhibitory learning during intermixed pre-exposure to AX and BX can account for both the Espinet and the perceptual learning effects.