The effect of petting on a classically conditioned emotional response

Three experimental conditions were introduced to five dogs who had formed a well-established conditional response to a tone-shock (T-S) sequence. During five of the trials the T-S sequence was presented while the dog was alone in the experimental room, five trials in which the T-S sequence was presented with a person present in the room, and five trials in which a person petted the dog during the T-S sequence and the 10 sec after the shock. It was observed that petting during the T-S sequence had a significant effect on the conditional and unconditional cardiac response. Instead of a tachycardia responce to the CS, the animals either showed a bradycardia or no change in HR during the CS. The same was true for the 10-sec period after the shock. Petting also reduced the conditional motor activity during the CS, and that activity usually elicited by shock.