Nonconscious associative learning: Pavlovian conditioning of skin conductance responses to masked fear-relevant facial stimuli.

We examined the possibility of nonconscious associative learning in a context of skin conductance conditioning, using emotional facial expressions as stimuli. In the first experiment, subjects were conditioned to a backwardly masked angry face that was followed by electric shock, with a masked happy face as the nonreinforced stimulus. In spite of the effectively masked conditioned stimuli, differential conditioned skin conductance responses were observed in a subsequent nonmasked extinction phase. This effect could not be attributed to differential sensitization or pseudo-conditioning. In the second experiment, the differential responding during extinction was replicated with angry but not with happy faces as conditioned stimuli. It was concluded that with fear-relevant facial expressions as the conditioned stimulus, associative learning was possible even in conditions where the subjects remained unaware of the conditioned stimulus and its relationship to the unconditioned stimulus.