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Recognising faces: effects of lighting direction, inversion, and brightness reversal.
Alan Johnston1, Harold Hill1, Nicole Carman1
1Department of Psychology, University College London, Gower Street, London WC1E 6BT, UK.
Perception
|March 8, 2014
Summary
The visual system prefers faces lit from above. Inverting faces lit from below reduces the typical face inversion effect, suggesting bottom lighting disrupts shape perception.
Area of Science:
- Visual perception
- Cognitive neuroscience
- Computational vision
Background:
- The visual system often interprets ambiguous 3D shape from shading and shadows with an assumption of top-down illumination.
- Face recognition is susceptible to effects of figural inversion and lighting orientation.
Purpose of the Study:
- To investigate whether the effects of figural inversion and lighting direction on face recognition are independent or interactive.
- To determine how illumination direction influences the face inversion effect.
Main Methods:
- Participants viewed images of faces under different lighting conditions (top-lit, bottom-lit) and orientations (upright, inverted).
- The effect of figural inversion on face recognition accuracy and/or response time was measured.
- The influence of lighting direction on the magnitude of the inversion effect was analyzed.
Main Results:
- A significant face inversion effect was observed for faces illuminated from above.
- The inversion effect was substantially reduced or eliminated for faces illuminated from below.
- A strong inversion effect was found for photographic negatives, irrespective of illumination direction.
Conclusions:
- Lighting faces from below appears to disrupt the formation of surface-based representations crucial for facial shape perception.
- The findings suggest an interaction between lighting orientation and figural inversion in face recognition.
- The results support the hypothesis that top-down illumination is a default assumption guiding the interpretation of facial geometry.
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