Pavlovian Conditioning to Social Stimuli

Using a Pavlovian procedure, human subjects were conditioned to pictures of angry faces with a mild electric shock as the unconditioned stimulus. They were then tested with backward masking conditions preventing conscious recognition of the facial stimuli. In the first experiment a shock followed a particular nonmasked angry face which was exposed among many other faces. Although the subjects did not rate this face as familiar in a subsequent test when is was presented masked among other masked and nonmasked faces, it elicited larger skin conductance responses than did nonshocked control faces. This dissociation between explicit recognition and implicit skin conductance differentiation was replicated in the second experiment, in which the subjects rated their shock expectancy. Although conditioning resulted in much better differentiation between conditioned and control faces during nonmasked than masked test-trials, skin conductance differentiation did not differ between the two masking conditions.