Acknowledgements: R.C.L., H.R., and D.C. thank Dr. Simon van Gaal and Prof. Robert McIntosh for their valuable comments and suggestions. R.C.L. thanks Dr. Johannes Fahrenfort, Dr. Maximilian Bruchmann, Prof. Stephen Fleming, Dr. Albert De Beir, and Dr. Brian Maniscalco for their useful technical advice. The authors thank Dr. Dalila Achoui for her technical guidance. R.C.L. was supported by an ANID/CONICYT PhD studentship, a British Psychological Society Postgraduate Study Visit Scheme award, a University of Edinburgh Principal’s Go Abroad Fund award, a Université libre de Bruxelles Seal of Excellence research fellowship, a Karolinska Institutet Strategic Research Area Neuroscience (StratNeuro) postdoctoral fellowship, and partially by a Karolinska Institutet postdoctoral stipend. A.C-J. was supported by an ANID/FONDECYT Regular (1240899) research grant. H.R. was supported by an Economic and Social Research Council (ESRC) future research leaders award (no. ES/L01064X/1). A.C. was supported by a European Research Council (ERC) advanced grant (EXPERIENCE – ADG101055060). D.C. was supported by an ERC advanced grant (X-SPECT – DLV692739).AbstractHuman vision can detect a single photon, but the minimal exposure required to extract meaning from stimulation remains unknown. This requirement cannot be characterised by stimulus energy, because the system is differentially sensitive to attributes defined by configuration rather than physical amplitude. Determining minimal exposure durations required for processing various stimulus attributes can thus reveal the system’s priorities. Using a tachistoscope enabling arbitrarily brief displays, we establish minimal durations for processing human faces, a stimulus category whose perception is associated with several well-characterised behavioural and neural markers. Neural and psychophysical measures show a sequence of distinct minimal exposures for stimulation detection, object-level detection, face-specific processing, and emotion-specific processing. Resolving ongoing debates, face orientation affects minimal exposure but emotional expression does not. Awareness emerges with detection, showing no evidence of subliminal perception. These findings inform theories of visual processing and awareness, elucidating the information to which the visual system is attuned.</jats:p
