CAFÉ WALL ILLUSION

   A term used to denote a marked wedge distortion that can be observed in horizontal rows of black and white tiles offset by half a tile width in alternating rows (a so-called Münsterberg che-querboard figure), with visible mortar lines in between the horizontal rows. The illusion consists of the horizontal mortar lines appearing as being tilted. The Café Wall illusion was first reported in 1979 by the British psychologists Richard Lang-ton Gregory (b. 1923) and Priscilla Heard. It had been brought to their attention by a member of Gregory's lab, who had observed it at the front of a café (St. Michael's Hill, Bristol, UK) which was adorned with black and white ceramic tiles. The mediation of the Café Wall illusion is attributed to a combination of simple image processing occurring at the retina, and complex processing carried out by the cortical cells of striate cortex. The Café Wall illusion is usually classified as a * physiological illusion.

   References

   Gregory, R.L., Heard, P. (1979) Border locking and the Café Wall illusion. Perception,8, 365-380.