Conflict, not category: What the pupil tracks in face pareidolia
Year: 2026
Type: preprint
Abstract: Illusory faces, the faces people see in inanimate objects, share the low-level image statistics of the objects they are made of while, nonetheless, being perceived as faces. Neural representations of illusory faces shift from face-like to object-like within roughly 200 ms, and observers explicitly categorise them as objects, yet the illusion remains compelling. We asked whether the pupil, a peripheral index of both light and arousal, is sensitive to this dual identity. Forty participants viewed sequences of human faces, illusory faces in objects, and matched non-face objects (100 images each) while performing an orthogonal task at fixation. Human faces and objects both evoked pupil constriction, whereas illusory faces produced dilation beginning at approximately 350 ms. Thus, rather than falling between faces and objects or resembling either category, illusory faces elicited a qualitatively different pupil response. This dissociation remained after controlling for luminance and emotional valence, despite luminance being the strongest determinant of pupil size. Critically, within the illusory images, the dilation scaled with independent measures of the strength of the face percept, including face-likeness and the probability of categorisation as a face, and did not diminish across repeated presentations. These findings are consistent with the pupil tracking the conflict between the object and face interpretations, rather than stimulus category per se. They suggest that although neural representations quickly settle on an object's veridical identity, the competing illusory face interpretation persists, revealing a physiological signature of the conflicting perceptual identities that define face pareidolia.
Source: PsyArXiv (OSF Preprints)
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7208713674