Do people prone to hallucinations expect to see faces in noise?
Healthy people who reported more hallucination-like experiences were more inclined to 'see' faces in visual noise and became aware of faces looking straight at them faster, fitting the idea that psychosis involves overly strong expectations for socially meaningful signals.
Source
Overly Strong Priors for Socially Meaningful Visual Signals Are Linked to Psychosis Proneness in Healthy Individuals
Study at a glance
- Design
- Cross-sectional — Correlational study in a non-clinical sample: questionnaire measures of psychosis proneness related to a Bayesian-modelled face-detection-in-noise task and a breaking continuous flash suppression (b-CFS) gaze task, using rank and Bayesian correlations
- N
- N=39 · Thirty-nine participants from the general population completed the face task; three were excluded from the gaze task (one technical problem, two with excessive suppression), leaving 36 for gaze analyses.
- Population
- Healthy adults recruited from the general population in Berlin, with relatively high psychosis-proneness scores
- Outcome
- Estimated prior and sensitivity for detecting faces in noise; direct-gaze bias (difference in breakthrough time for averted versus direct gaze); correlations with Peters Delusion Inventory and Cardiff Anomalous Perceptions Scale scores
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What they did
Thirty-nine adults from the general population completed questionnaires measuring delusion proneness and anomalous (hallucination-like) perceptual experiences. In a face task they judged whether each noisy image contained a face (40 images hid a real face and 60 were pure noise); a Bayesian model separated each person's prior expectation of faces from their sensitivity to real faces. In a gaze task, faces with direct or averted gaze were shown to one eye while flashing masks were shown to the other (continuous flash suppression), and the researchers timed how long each face took to break into awareness.
What they found
A stronger prior for detecting faces correlated with both hallucination proneness (r = 0.496) and delusion proneness (r = 0.461), whereas sensitivity to real faces was unrelated to either, so the effect was a bias rather than better or worse vision. Across the sample, faces with direct gaze broke through suppression faster than averted-gaze faces (on average 3.385 versus 4.055 seconds). The size of this direct-gaze advantage correlated with hallucination proneness (r = 0.429) but not significantly with delusion proneness.
The limits
What it doesn't show
The sample was small and consisted only of healthy volunteers, so the authors note a study in people with psychosis is needed to confirm that the findings apply clinically. The design is correlational, so it cannot show that strong priors cause hallucination-like experiences. Because only face stimuli were used, the study cannot tell whether the bias is specific to social signals or reflects a general tendency to see meaning in noise; the authors call for a non-social control condition. The 'prior' is inferred from behaviour, not experimentally manipulated, and the evidence for the gaze–hallucination link was only substantial rather than strong.
Key terms
- Prior (predictive coding)
- The brain's expectation about what is out there before looking; strong-prior accounts propose that overly strong expectations make people perceive things that are not present.
- Psychosis continuum
- The view that psychotic experiences vary continuously in the general population, with clinical psychosis at the extreme end.
- Continuous flash suppression (CFS)
- A technique in which rapidly changing masks shown to one eye keep a stimulus shown to the other eye out of awareness for a time.
- Breakthrough time
- How long a suppressed stimulus takes to become consciously visible under CFS, used as a measure of how readily it gains access to awareness.
- Sensitivity vs bias
- Sensitivity is how well someone tells real signals from noise; bias (here the prior) is how inclined they are to say a signal is present regardless.
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Quiz yourself
What did the face-in-noise task show about people high in psychosis proneness?
Common questions
Why study healthy people rather than patients?
Psychosis proneness varies in the general population and shares risk factors with clinical psychosis, so healthy samples avoid confounds such as medication while still probing the same processes.
Why does it matter that sensitivity was unrelated to psychosis proneness?
It shows prone individuals were not simply worse or better at seeing faces; they were more inclined to report faces, which is what a strong-prior account predicts.
What does the gaze task add?
Because faces were suppressed from awareness, it suggests the bias toward socially meaningful signals may act at early, unconscious stages of processing, not just at later interpretation.
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