When presentation of a retractable lever always preceded food delivery, rats licked or gnawed the lever. They also approached but seldom orally contacted a lever signaling brain-stimulation reinforcement; instead, subjects sniffed, pawed, or "explored" the lever. Therefore, a Pavlovian conditioned stimulus evoked directed skeletal responses whose specific form depended on the forthcoming unconditioned stimulus.

Hooded rats with hippocampal lesions, with neocortical lesions, or with no lesions received either 0 or 30 presentations (preexposures) of a stimulus later used as CS in a two-way shuttle-avoidance task. The 30 preexposures slowed acquisition of the avoidance response and speeded its extinction in the unoperated control group and in the group with neocortical lesions, but not in the group with hippocampal lesions. The latter group did not differ on either measures from any of the subgroups that received 0 preexposures, none of which differed from each other. The results are viewed as support for models attributing an inhibitory function to the hippocampus and suggest an attentional involvement in the preexposure effect.

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