Café Wall Illusion

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The Café Wall Illusion: The horizontal lines are exactly parallel.

The Café Wall Illusion (English for "Café-Wall-Illusion" , also called coffee house illusion ) is a visual perception illusion in which rectangles appear trapezoidal when they alternate between dark and light, forming parallel rows and shifting them against each other and using gray lines are separated.

history

It was first published in 1898 by Pierce under the name Kindergarten illusion (known in German-speaking countries as Kindergarten-Braided-Pattern-Deception ). After Gregory it was discovered by Steve Simpson in 1973 on the outside facade of a café in Bristol .

observation

The rectangles are perceived as trapezoidal, and most of all when the dividing line is gray. The line width plays an important role. Gregory and Heard (1979) found an increase in the effect down to the smallest line width they examined of 1 arc minute . Thin black lines that appear gray due to diffraction also show the illusion. There is a pronounced dependence on the line width, with a maximum of 0.5 arc minutes.

Interpretations

  • Pierce explains the deception about the irradiation effect , just as Münsterberg had interpreted the shifted chessboard figure he had discovered shortly before. Then the corners of the light areas seem to penetrate into the dark areas, so that the dividing lines seem to run obliquely to their real direction. In fact, the illusion is largely attenuated if the rectangles are shown in different colors but with the same brightness.
  • Gregory and Heard blame the border locking phenomenon. They assume that signals are triggered at a cut-off line, which on the one hand connect the two brightness areas to form a perceptual unit, but can also be easily disturbed and thus lead to false perceptions.
  • A subjective contour connects areas of comparable perceived brightness
    McCourt sees the cause of the deception in the formation of subjective contours. These connect areas that are perceived as comparably bright. One of these contours can, for. B. form a bridge between two light rectangles in adjacent rows if the part of the gray dividing line is included that lies between the black areas above and below and therefore appears lighter. This contour (indicated in red in the picture on the right) then runs at an angle to the actual direction of the dividing line and takes on its function in perception. In the example here, using a variant with continuous shading, an extra-wide gray line shows how this effect occurs. In perception, however, this only happens with a very narrow dividing line at or below the resolution limit, which does not clearly stand out as an independent object from the environment.
  • Morgan and Moulden assume that bandpass filtering in the visual system is the cause.
  • Kitaoka performs the illusion back to being in a corner of 90 ° - angle is perceived as less and this explains both the classical form as well as an example with a continuous change in brightness. Kitaoka, Pinna and Brelstaff introduce the concept of contrast polarities for explanation .

Difference to the Münsterberg illusion

The different periodicity of neighboring rows makes the boundaries appear wavy.

In the Münsterberg illusion , only two rows of pure black squares on a light background, with a black line running between them, can be seen, while the Café Wall Illusion consists of several rows of rectangles separated by gray lines. It is also sometimes referred to as the more general form of the Munsterberg illusion.

variants

If neighboring rows differ in their periodicity, then the dividing lines no longer appear uniformly oblique, but rather wavy. Kitaoka, Pinna and Brelstaff released several variants in a spiral form.

Web links

Individual evidence

  1. ↑ Michael Bach, Michael Bach: Coffee house deception. Retrieved January 23, 2020 .
  2. ^ Pierce, AH (1898). The illusions of the kindergarten patterns. Psychological Review 5 (3): 233-53. doi : 10.1037 / h0070595 .
  3. ↑ a b Gregory, RL; Heard, P. (1979). Border locking and the Café Wall illusion (PDF). Perception 8 (4): 365-80. doi : 10.1068 / p080365 .
  4. ↑ Kreiner, WA (2012). Subjective contours triggered by border lines below the resolution limit. doi : 10.18725 / OPARU-2596 .
  5. ^ Pierce, AH (1901). Studies in Auditory and Visual Space Perception . London: Longmans Green.
  6. ↑ Münsterberg, H (1897). The displaced chess board piece. Journal of Psychology and Physiology of the Sensory Organs 15, 184–188.
  7. ↑ Westheimer, G (2007). Irradiation, border location and the shifted-chessboard pattern. Perception 36, 483-94. doi : 10.1068 / p5646 .
  8. ^ McCourt, EM (1983). Brightness induction and the Café Wall illusion. Perception 12, 131-142.
  9. ↑ Morgan, MJ and Moulden, B (1986). The Münsterberg Figure and Twisted Cords. Vis. Res., 26, 1793-1800.
  10. ^ Kitaoka, A (1998). Apparent contraction of edge angles. Perception 27, 1209-1219.
  11. ↑ Kitaoka, A; Pinna, B .; Brelstaff, G (2004). Contrast polarities determine the direction of Cafe Wall tilts. Perception 33 (1), 11-20. doi : 10.1068 / p3346 .
  12. ↑ Kitaoka, A; Pinna, B, & Brelstaff, G (2001). Last but not least. Perception 30, 637-646.