In the present study, we examine using signal detection theoretic measures to what extent subliminal perception is independent of subjective introspection. The neural mechanisms that enable this subliminal capacity are not well understood, and debate continues on whether subliminal perception reveals a truly unconscious capacity that functions independent of conscious perception. Interestingly, visual stimuli that individuals report as not consciously perceived can sometimes influence their behavior, a phenomenon known as subliminal or unconscious perception (Hannula et al., 2005 Kouider & Dehaene, 2007 Phillips, 2018 Stein & Peelen, 2021).

One of the major aims of neuroscience is to uncover which neural processes enable a person to consciously experience and respond to stimuli in their environment. Altogether, our results suggest that rather than being a separate unconscious capacity, subliminal perception is based on similar processes as conscious vision. We show that the accuracy of discriminating the location of a subliminal stimulus could be predicted with relatively high accuracy (AUC = 0.70) based on lateralized electroencephalographic (EEG) activity before the stimulus, the hemifield where the stimulus was presented, and the accuracy of previous trial's discrimination response. Signal detection analyses indicated that while subjects categorized their percepts as “unconscious,” their capacity to discriminate these stimuli lay on the same continuum as conscious vision. Consistent with previous studies, participants correctly discriminated with slightly above chance-level accuracy the location of a stimulus they reported not seeing. We asked participants to discriminate the location of a briefly presented low-contrast visual stimulus and then rate how well they saw the stimulus. Instead, here we asked to what extent neural activity before stimulus presentation influences subliminal perception.

This phenomenon is known as “subliminal perception.” Such capacity is often assumed to be relatively automatic in nature and rely on stimulus-driven activity in low-level cortical areas. Individuals are able to discriminate visual stimuli they report not consciously seeing.

Subliminal stimulus