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 face's 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 face's 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.

Subliminal perception is continuous with conscious vision and can be predicted from prestimulus electroencephalographic activity

“…Part of the difficulty in answering whether the signals on which the participants based their responses on subliminal trials were unconscious or not is that it requires us to artificially binarize a process that is in truth continuous. Our finding is in line with the observation that when a paradigm is used which minimizes the participants' need to specify a criterion to label something as “conscious” or “unconscious,” no evidence for strictly unconscious perception is observed (Peters & Lau, 2015; Rajananda et al, 2020). Also, objective visual discrimination behavior and subjectively experienced perception evoked nearly identical ERP/ERSP responses, suggesting that the two are not strongly dissociated.…”

“…Koivisto and Grassini (2016) reported that the ERP correlate of subliminal discrimination also correlated with conservative response criterion, suggesting that what the participants labeled “not seen” may have been severely degraded conscious perception. This is consistent with the results of Peters and Lau (2015), which suggest that when perception is measured using a procedure that minimizes the influence of criterion setting, no evidence for strictly subliminal perception is observed (see also Rajananda et al, 2020).…”

The metaperceptual function: Exploring dissociations between confidence and task performance with type 2 psychometric curves

“…blindsight-like behavior (Weiskrantz, 1986) . Future studies may compare the magnitude of MPDC effects near chance performance to the effect size of observed divergence between performance and confidence at low levels of d' as predicted by ideal observer models (Knotts et al, 2018;Peters, Fesi, et al, 2017;Peters & Lau, 2015;Rajananda et al, 2018) .…”