Normal observers show no evidence for blindsight in facial emotion perception

Abstract

It is commonly assumed that normal human observers can exhibit blindsight-like behavior: the ability to discriminate or identify a stimulus without being aware of it. However, we recently used a bias-free task to show that what looks like blindsight may in fact be an artifact of typical experimental paradigms susceptibility to response bias. While those findings challenge many previous reports of blindsight in normal observers, they do not rule out the possibility that different stimuli or techniques could reveal such perception without awareness. One particularly intriguing candidate for this unconscious perception is emotion processing, as processing of emotional stimuli (e.g. fearful/happy faces) has been reported to potentially bypass conscious visual circuits. Here we used the bias-free blindsight paradigm to investigate whether emotion processing might reveal featural blindsight, i.e. the ability to identify a faces emotion without having introspective access to the task-relevant features of the face that led to the discrimination decision. However, despite the purported ability of emotional stimuli to bypass conscious visual processing, we saw no evidence for such emotion processing featural blindsight: like in our previous study, as soon as participants could identify a faces emotion they reported introspective access to the task-relevant features, matching predictions of a Bayesian ideal observer. The present results challenge dominant theory, adding to the growing body of evidence that perceptual discrimination ability in the complete absence of introspective access may not be possible for neurologically intact observers.