Fear conditioned with escapable and inescapable shock: Effects of a feedback stimulus

Four experiments, with 140 male Fischer rats, compared the level of fear conditioned with escapable and inescapable shock. In Exps I and II, master Ss that had received 50 unsignaled escapable shocks were less afraid of the situation where the shock had occurred than were yoked Ss that had received inescapable shocks. Comparable results were found in Exps III and IV, which used freezing as an index of fear of a discrete CS that had been paired with shock. Control per se was not necessary to produce the low level of fear seen in the master Ss. Yoked groups receiving a feedback signal at the time the master made an escape response showed a low level of fear that was comparable to that of the masters and significantly less than that seen in the yoked Ss without feedback. In addition, there were strong suggestions that control and feedback exert their effects through the same or highly similar mechanisms. Possible explanations for how control and the exteroceptive feedback signal produce this effect are discussed. (35 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).