Abstract
[Subjects] Ss received avoidance training to a visual signal in a shuttle box, and, while immobilized with tubocurarine chloride, were given Pavlovian fear conditioning with 2 tones. The 2 different tone CSs [conditional stimulus] were of equal duration; a trace procedure was used wherein 1 was paired with a 0.5-sec. shock and 1 with a 50.0-sec. shock. During Pavlovian fear conditioning, EKGs [Electrocardiogram] were recorded. Later, in the shuttle box, Ss were tested during avoidance extinction with all 3 stimuli. Even though Ss did not show differential cardiac conditioning to the tones, they hurdled the barrier more quickly in response to the tone previously paired with the 50.0-sec. shock than to the tone paired with the 0.5-sec. shock.

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