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Capturing lightness between contours.

Mark Vergeer1, Rob van Lier

  • 1Donders Institute for Brain, Cognition and Behaviour, Centre for Cognition, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands. m.vergeer@donders.ru.nl

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Summary
This summary is machine-generated.

Thin outlines at intersections of distorted Hermann grids create illusory lightness differences, similar to the original Hermann grid illusion. These effects persist even in foveal vision, suggesting lateral inhibition and contour interactions play a key role.

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Area of Science:

  • Visual perception
  • Neuroscience of vision
  • Psychophysics

Background:

  • The Hermann grid illusion demonstrates illusory dark patches at intersections of white bars on a black background.
  • These illusory effects persist even with outlines at intersections and in foveal vision.
  • Distorting Hermann grid contours typically eliminates these illusory spots.

Purpose of the Study:

  • To investigate if thin outlines on distorted Hermann grids can reintroduce illusory lightness differences.
  • To determine if these induced effects are similar to the original Hermann grid illusion.
  • To explore the role of luminance polarity, contour shape, and visual field in these phenomena.

Main Methods:

  • Presenting distorted Hermann grid configurations with thin outlines at intersections.
  • Conducting experiments in foveal vision using simple two-bar displays.
  • Varying luminance polarity and contour shapes at intersections.

Main Results:

  • Thin outlines on distorted Hermann grids induce lightness differences in the same direction as the original Hermann grid illusion.
  • These induced lightness differences are visible in foveal vision.
  • The effects are independent of luminance polarity and contour shape at the intersection.

Conclusions:

  • Lateral inhibition combined with spreading and capturing of luminance differences by contours explains the induced effects.
  • Contour interactions, potentially similar to those in peripheral vision for the original Hermann grid, are crucial.
  • Illusory lightness perception can be modulated by contour geometry and visual processing mechanisms.