Orienting and Defensive Responding in the Electrodermal System: Palmar-Dorsal Differences and Recovery Rate during Conditioning to Potentially Phobic Stimuli

It was suggested that the effects of fear-relevant pictures as conditioned stimuli (CSs) for electrodermal responses may be explained if it is assumed that they produce conditioned defense responses (DRs), as opposed to the orienting responses (ORs) that are produced by fear-irrelevant stimuli. Some propositions in Edelberg's theory of electrodermal activity were used to differentiate between DRs and ORs in a test of this hypothesis. Groups of subjects were conditioned to fear-relevant (snakes and spiders) or fear-irrelevant (flowers and mushrooms) CSs by means of an aversive (electric shock) or a non-aversive (imperative signal for a reaction time (RT) task) unconditioned stimulus in long interval differential paradigms. The neutral-shock, phobic-RT, and neutral-RT groups showed no palmar-dorsal differences either in magnitude, probability or amplitude, and no conditioning in the recovery rate measure. However, the phobic-shock group showed a peak of dorsal magnitude early in training that subsequently habituated whereas the palmar magnitude data indicated a gradual conditioning effect that lasted throughout the 20 extinction trials. In addition, it showed slower recovery to the reinforced than to the nonreinforced stimulus. These data are taken as support for the hypothesis.