Facilitation of visual processing by masked presentation of a conditioned facial stimulus

We tested whether a conditioned emotional stimulus could facilitate visual processing when presented subliminally. Participants received Pavlovian conditioning in which a fearful expression (conditioned stimulus) was paired with electric finger shock (unconditioned stimulus). In a subsequent session, they were subject to a simple perceptual task involving subliminal presentation of facial expressions followed by a simple color patch. Although none of the participants reported conscious detection of the facial stimuli, early posterior negativity was significantly enhanced to the conditioned fear face and the neutral face of the same identity. Paralleling the brain activity, reaction times to the conditioned stimulus faces were also facilitated. These results suggest that conditioned threat stimuli can facilitate perceptual processing even when they are processed unconsciously.