Simultaneous and successive associations in sensory preconditioning.

Four experiments used a novel stimulus sequence to compare simultaneous and sequential associations among neutral stimuli in a sensory preconditioning procedure. In Experiments 1, 2, and 4, rats received a sequence of the form AB-B' in which A was simultaneous with B but sequential with B'. Subsequently, either B or B' was conditioned, and the response to A assessed. This procedure matches the context of A's presentation in comparing its sequential association with B' and its simultaneous association with B, something that prior paradigms have neglected. Experiment 3 used an analogous B'-AB procedure to compare simultaneous and backward associations. Experiments 1-3 used a flavor-aversion procedure in which A, B, and B' were flavors and lithium chloride was the reinforcer. Experiment 4 used conditioned suppression with auditory and visual stimuli and shock reinforcer. All four experiments found simultaneous associations between A and B to be substantial. Moreover, in all cases, conditioning of B produced a greater response to A than did conditioning to B', which suggests that simultaneous associations are stronger than are sequential ones when this paradigm is employed.