Unconscious processing of threatening stimuli: behavioural and physiological evidence

Research on unconscious perception has demonstrated an advantage in the processing of evolutionary threatening animals. Higher detection abilities and stronger electrodermal activity have been observed when snake and spider images were presented subliminally and compared to innocuous stimuli. These reactions were further enhanced in participants with higher levels of phobia towards these animals. However, more recent research has challenged this view, demonstrating no clear advantage of threatening animals over innocuous stimuli. The present study investigated the unconscious processing of evolutionary threatening animals in both healthy and phobic participants. Snake and spider images were presented using the “breaking Continuous Flash Suppression” (bCFS) paradigm, allowing for their prolonged suppression from visual awareness. We recorded the time required for the stimuli to break through suppression, as well as electrodermal activity, facial electromyography, and pupil dilation. Moreover, we administered the Perceptual Awareness Scale and a recognition task at the end of each trial. Participants also completed three questionnaires assessing their levels of arachnophobia, ophidiophobia, and negative emotions. We found faster breakthrough times for snakes compared to spiders, as well as faster detection of intact images compared to their scrambled counterparts. Intact images were associated with stronger electrodermal activity compared to scrambled ones, independently of awareness. Interestingly, nonphobic participants showed faster breakthrough times for intact spider images than for scrambled ones, whereas arachnophobes did not exhibit this advantage. Overall, our results support the existence of a subcortical pathway that facilitates a preattentive processing of threatening stimuli and highlight distinct processing patterns in phobic individuals.