Illuminating the Unconscious: Physical and Perceived Brightness in Cognitive Processing

Abstract

This study investigated how physical luminance and perceived brightness affect breakthrough time (BT) under continuous flash suppression (CFS). Experiment 1 examined whether the glare illusion--which increases subjective brightness without altering actual luminance--would shorten BT compared to physically identical controls. The results revealed no difference, suggesting that subjective brightness alone does not expedite emergence into awareness. Experiment 2 assessed whether the partial suppression of the illusions inducers influenced detection speed and revealed that subjective brightness stimuli gained a BT advantage. Experiment 3 tested participants ability to discriminate real versus illusory brightness while stimuli remained suppressed; performance above chance for both conditions indicated that physical and perceived brightness cues were processed unconsciously. Together, these findings suggest that contextual brightness illusions are not simply lost below awareness--they can be discriminated in unconscious vision. Statement of RelevanceUnderstanding how the visual system processes brightness illusions--even prior to awareness--is crucial for uncovering the brains deeper mechanisms of perception. This research clarifies the limits of unconscious visual processing by showing that illusions can be registered without consciousness but do not necessarily expedite emergence into awareness. These insights advance theoretical models of hierarchical vision and demonstrate that while early cortical areas prioritize actual luminance in determining whether a stimulus reaches awareness, higher areas can still encode illusory brightness beneath the threshold of consciousness. Thus, the studys findings have broad implications for both basic neuroscience--refining how we think about the boundary between unconscious and conscious perception--and for applied fields seeking to harness or mitigate perceptual illusions. Research Transparency StatementO_ST_ABSPreregistrationC_ST_ABSAll experiments were not preregistered. Conflicts of interestThe authors declare that they have no competing interests. Data availabilityThe code and data underlying the results presented in the study are available from the Open Science Framework repository (https://osf.io/u5der/). EthicsThe Committee for Human Research of the Toyohashi University of Technology approved the experiments (2023-20). Written informed consent was obtained from all participants after the procedural details were explained to them. FundingThis work was supported by JSPS KAKENHI (Grant Numbers JP22K17987 to H.T., JP24H01551 to T.M., JP23KK0183 to T.M., JP20H05956 to S.N.), JSPS Grant-in-Aid for JSPS Fellows (Grant Number JP24KJ1313), and Young Principal Investigator fund JPMJFS2121. Artificial intelligenceDuring the preparation of this work, the authors used ChatGPT o1 and Grammarly to improve the language, and the manuscript was proofread by native English speakers through an English editing service. After using the tool and service, the authors reviewed and edited the content as needed, and they take full responsibility for the content of the publication.