Cognitive Psychology

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VIWO 2.0 A Windows® program for demonstrating visual-perception phenomena

VIWO (Visual World) is a program that can be used for the demonstration of various perceptual phenomena, and for the variation of some parameters that control the appearance of the stimuli.

Included are:

  • geometrical-optical illusions (Müller-Lyer, Delboeuf, Hering, Orbison, Zöllner, etc.),
  • subjective contours (Kanizsa-Triangle, -Square, contours induced by shadows, etc.),
  • Gestalt perception (grouping by proximity and similarity, common fate, etc.),
  • apparent movement (Phi, Ternus, waterfall illusion, etc.),
  • color phenomena (Glass suite, color mixtures, color contrast, assimilation, etc.),
  • contrast phenomena (Mach bands, Hermann grid, etc.),
  • monocular depth perception (gradients, occlusion, rotating Necker cube, etc.),
  • binocular depth perception (anaglyphs).

One of the most interesting features of the program is that for many phenomena  parameters can be varied interactively. For instance, apparent movement is demonstrated by presenting simple objects in rapid succession at different positions. By changing the size of the display window one can modify the size of the objects and their distance. Moreover, also the time interval between the object presentations, as well as the color and form of the object at one position can be modified. The latter leads to the illusion that the object changes its color and/or form during its (apparent) movement.

For each phenomena there is a description which includes references to the literature.

Hübner, R. (1997). "Visuelle Welt": A Windows program for demonstrating visual-perception phenomena. Spatial Vision, 11, 103-106.


See also the program VIAT.