Following classical fear conditioning, Ss were trained to jump a hurdle to escape the fear-eliciting stimuli. 2 groups were conditioned in the start box of the hurdle apparatus (Same CB) and 2 in a separate, but similar, conditioning box (Diff CB). Under each condition, 1 group had hurdle training after a 3-min., and the other, after a 24-hr., postconditioning delay. For the 2 Diff CB groups, hurdle training involved a generalized stimulus situation. All groups, except Group 3 min.-Diff CB, learned to jump the hurdle in 25 trials. The significant improvement in performance with an increase in postconditioning delay under the Diff CB, but not under the Same CB, condition was attributed to an increase in the strength of the fear response over time to generalized, but not to the original, stimuli.
Shock intensity (.3 or 1.6 ma.) was combined faotorially with ITI (15, 30, or 45 sec.) in a shuttle-box avoidance task (n -20/group). Following 65 avoidance trials, rats were allowed, in the absence of both shock and the CS, to jump from one compartment of the shuttle box to an adjacent safe box. The 1.6-ma. groups made significantly fewer avoidance responses than the ,3-ma. groups but jumped into the safe box with significantly shorter latencies. The latter finding is contrary to ari interpretation of the inverse relationship between shuttle-box avoidance learning and shock intensity which is based on freezing responses but supports a reinforcement interpretation which emphasizes the role of fear of situational cues.That there is an inverse relationship between strength of shock and avoidance learning by rats in a shuttle box is well documented (e.g.,
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