The Behavioral and brain sciences
July 22, 2025
François Stockart, Maor Schreiber, Pietro Amerio et al.
20 citations
The scope of unconscious processing remains hotly debated, driven by diverse methods for manipulating and measuring perceptual awareness. Through dialogue among researchers with varied theoretical backgrounds, ten recommendations and nine outstanding issues are provided for designing experimental paradigms, analyzing data, and reporting results. These guidelines aim to evoke discussion about norms in studying unconscious processes and help researchers make informed decisions. While some recommendations may not align with existing approaches and will likely evolve, they are intended to foster a more convergent understanding of the extent and limits of unconscious processing.
eLife
May 28, 2025
Johannes Jacobus Fahrenfort, Philippa A Johnson, Niels A Kloosterman et al.
10 citations
Conservative response criterion placement unexpectedly inflates effect sizes in neural measures of both conscious and unconscious processing, while liberal criterion placement reduces them. Simulations and electroencephalography decoding analyses from two studies using common subjective awareness indicators confirm these confounding effects. The widely used Perceptual Awareness Scale (PAS) does not protect against criterion confounds. Follow-up simulations show that the experimental context determines whether the confounding effect is larger for conscious or unconscious neural measures. Criterion placement threatens the construct validity of neural measures of consciousness.
Cognitive neuroscience
January 1, 2021
Johannes J. Fahrenfort, Simon van Gaal
10 citations
A functionalist criterion for arbitrating between theories of consciousness is not theory-neutral because it focuses on functional equivalence between systems. Empirical theories of consciousness are mechanistic rather than functionalist, so such criteria are not helpful for arbitration.
Communications psychology
May 21, 2025
Nicolás Sánchez-Fuenzalida, Simon van Gaal, Stephen M Fleming et al.
3 citations
Confidence reports during perceptual decision-making do not uniquely reflect subjective experience. Across two experiments with 204 participants and three bias manipulations, non-perceptual factors such as changes in stimulus base rates or asymmetric payoff matrices leaked into confidence judgments. This shows that confidence can be influenced by response biases unrelated to actual perception, complicating its use as a pure measure of subjective experience. The relative strength of biases in first-order choices versus confidence may help distinguish whether a manipulation truly alters perception or only affects decision strategy.
eLife
June 18, 2025
Samuel Noorman, Timo Stein, Jasper Zantvoord et al.
2 citations
Perceptual inference—how the brain integrates visual features into a coherent whole—depends on recurrent processing, the back-and-forth communication between higher and lower cortical regions. Animal studies have implicated NMDA receptors in this process, but human evidence was lacking. In two double-blind, placebo-controlled experiments with healthy participants, the NMDA receptor antagonist memantine selectively improved the brain's ability to decode complex visual illusions (Kanizsa triangles) that require recurrent processing, while leaving simpler visual processing (contrast and collinearity) unaffected. This enhancement occurred only when stimuli were attended and consciously perceived. The findings suggest that blocking NMDA receptors can enhance recurrent processing for attended objects, linking animal and human research on the neural basis of conscious perception.
PLoS biology
July 1, 2025
Simon van Gaal
1 citation
A new pre-registered study in PLOS Biology compares several proposed neuronal markers of loss of consciousness in flies across three global brain states: awake, asleep, and anesthetized. The work evaluates which neural markers can differentiate these states, testing markers previously suggested to underlie states of consciousness. The findings indicate which markers reliably distinguish between wakefulness, sleep, and anesthesia in the fly model.
Nature communications
May 8, 2026
Nicolás Sánchez-Fuenzalida, Chris Jungerius, Stephen M Fleming et al.
A key challenge in consciousness research is separating genuine conscious perception from non-perceptual biases when observers report whether they saw a stimulus. In experiments with 505 participants who detected and reproduced dim or absent visual patterns under different conditions—attentional cues, asymmetrical base rates, and payoff schemes—a Hurdle-Gaussian model decomposed responses into a perceptual continuous component and a non-perceptual hurdle component. Statistical priors and reward structures shifted the non-perceptual hurdle, while attentional cues selectively shifted the perceptual component, consistent with changes in conscious experience. Crucially, including detection trials contaminated reproduction reports with non-perceptual criterion effects, urging caution in interpreting detection-based measures in consciousness research.
bioRxiv Preprint Server
February 22, 2024
Johannes J. Fahrenfort, Philippa A. Johnson, Niels A. Kloosterman et al.
preprint
Conservative criterion placement in subjective awareness judgments inflates neural effect sizes for both conscious and unconscious processing, while liberal placement reduces them. Simulations and two EEG studies show that the commonly used Perceptual Awareness Scale does not protect against this confound. The findings indicate that response criterion placement threatens the construct validity of neural measures of consciousness.
PLoS biology
May 1, 2021
Timo Stein, Daniel Kaiser, Johannes J Fahrenfort et al.
How unconscious processing is measured—either by asking participants what they saw (subjective) or by testing whether they can discriminate stimuli (objective)—affects conclusions about the brain's representation of unseen information. Using fMRI in 43 people viewing masked faces and houses that were either subjectively or objectively invisible, category information was found in early and higher visual cortex even for objectively invisible stimuli, though representations in anterior ventrotemporal areas were weaker. For subjectively invisible stimuli, a clear posterior-to-anterior gradient appeared, with stronger category information in ventrotemporal cortex. For objectively invisible stimuli, category information remained similar across visual areas. The measurement approach thus influences the extent of unconscious processing and the neural correlates of consciousness.