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Impact Factor:0.917 | Ranking:Psychology 64 out of 76 | Psychology, Experimental 80 out of 85
Source:2016 Release of Journal Citation Reports, Source: 2015 Web of Science Data

Border Locking and the Café Wall Illusion

  1. Richard L Gregory
  2. Priscilla Heard
  1. Brain and Perception Laboratory, University of Bristol, Department of Anatomy, The Medical School, University Walk, Bristol BS8 1TD, England


The Café Wall illusion (seen on the tiles of a local café) is a Münsterberg chequerboard figure, but with horizontal parallel lines which may have any luminance separating the rows of displaced squares. These (the ‘mortar’ lines) display marked wedge distortion which is especially affected by: contrast of the squares (‘tiles’); width of the ‘mortar’ lines, and their luminance which must not be significantly higher than that of the light squares or lower than that of the dark squares for distortion to occur. An experiment is described from which quantitative data have been obtained by varying these parameters. It is suggested that contiguous regions of different luminance (and contiguous colour regions) are normally held in spatial register by locking from common luminance boundaries. The Café Wall illusion is attributed to this border locking producing inappropriate contour shifts from neighbouring regions of contrasting luminance when separated by narrow gaps of neutral luminance. Further implications on the border-locking notion are discussed.

  • Received August 1, 1979.
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