I am blind, but I "see" fear

The ability to process unseen emotional signals might offer an evolutionary advantage in enabling threat-detection. In the present study, patients with visual field defects, without any subjective awareness of stimuli presented in the blind field and performing at the chance level in two alternative discrimination tasks (Experiment 1), were tested with go-no go tasks where they were asked to discriminate the emotional valence (Experiment 2) or the gender (Experiment 3) of faces displayed in the intact field, during the concurrent presentation of emotional faces in the blind field. The results showed a facilitative effect when fearful faces were presented in the blind field, both when the emotional content of the stimuli was relevant (Experiment 2) and irrelevant (Experiment 3) to the task. These findings are in contrast with performances of healthy subjects and patients tested in classical blindsight investigations, who showed response facilitation for congruent pairs of emotional stimuli. The observed implicit visual processing for unseen fearful stimuli might represent an adaptive mechanism for the implementation of efficient defensive responses, probably mediated by a spared sub-cortical and short-latency pathway.