Automatically elicited fear: Conditioned skin conductance responses to masked facial expressions

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Abstract
This study examined automatic elicitation of conditioned skin conductance responses (SCRs), when a backward masking procedure prevented the subject's conscious awareness of the conditioned stimuli (CSs). The CSs were pictures of emotional facial expressions. A differential conditioning procedure was used. One facial expression (e.g. an angry face) was aversively conditioned by a shock unconditioned stimulus, whereas another facial expression (e.g. a happy face) was never presented with the shock. After conditioning, the CSs were presented backwardly masked by a neutral face. This procedure prevented conscious perception of the CS. Nevertheless, reliable differential SCRs were obtained when the CS had been an angry face. This effect, however, was dependent on the subject's direction of attention. When attention was focused on the mask, no differential responding was observed. Thus it was concluded that, when fear-relevant stimuli (angry faces) served as the CS, elicitation of SCRs was automatic in the sense that it was possible even when the subjects were not aware of the stimuli presented. However, it was only partially automatic because the effect was modified by attention.