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Related Experiment Video

Updated: Jun 21, 2026

Perceptual and Category Processing of the Uncanny Valley Hypothesis' Dimension of Human Likeness: Some Methodological Issues
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Curvature coding in illusory contours.

Elena Gheorghiu1, Frederick A A Kingdom, Manpreet Sull

  • 1McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada H3A 1A1. elena.gheorghiu@mcgill.ca

Vision Research
|August 18, 2009
PubMed
Summary
This summary is machine-generated.

Shape after-effects reveal that illusory contours use a subset of real contour mechanisms, suggesting distinct processing pathways. Illusory curvature mechanisms lack tuning to carrier properties like contrast or orientation.

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Area of Science:

  • Visual perception
  • Neuroscience
  • Computational vision

Background:

  • The perception of visual contours, both real and illusory, is fundamental to object recognition.
  • Mechanisms sensitive to curvature are proposed to underlie shape after-effects, influencing perceived contour properties.

Purpose of the Study:

  • To determine if illusory and real contours share processing mechanisms using shape after-effects.
  • To investigate the carrier-tuning properties of mechanisms processing illusory curvature.

Main Methods:

  • Employed shape frequency after-effect (SFAE) and shape amplitude after-effect (SAAE) paradigms.
  • Utilized sinusoidal-shaped illusory and real contours with varying carrier properties (luminance contrast-polarity, scale, orientation).
  • Compared after-effects between real and illusory contour adaptor-test combinations.

Main Results:

  • Both SFAE and SAAE were observed for illusory contours.
  • Real contour adaptation produced significant after-effects on illusory contour tests.
  • Illusory contour adaptation produced weaker after-effects on real contour tests, indicating asymmetry.
  • Illusory curvature processing showed no selectivity for carrier luminance contrast, scale, or orientation.

Conclusions:

  • Illusory contour shape is processed by a subset of mechanisms involved in real contour processing.
  • The observed asymmetry suggests distinct, though overlapping, neural substrates for real and illusory contour perception.
  • Illusory curvature mechanisms are broadly tuned to carrier properties, unlike mechanisms for real contours.