December 2001
Volume 1, Issue 3
Vision Sciences Society Annual Meeting Abstract  |   December 2001
Kanizsa's paradox revisited
Author Affiliations
  • T. Agostini
    Department of Psychology, University of Trieste, Trieste, Italy
  • D. Daris
    Department of Psychology, University of Trieste, Trieste, Italy
  • A. Galmonte
    Department of Psychology, University of Trieste, Trieste, Italy
Journal of Vision December 2001, Vol.1, 424. doi:
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      T. Agostini, D. Daris, A. Galmonte; Kanizsa's paradox revisited. Journal of Vision 2001;1(3):424.

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      © ARVO (1962-2015); The Authors (2016-present)

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Introduction. In 1954, Kanizsa offered a demonstration of a paradoxical situation in the domain of color appearance. The demonstration of the paradox is articulated in two parts. In the first part, two gray surfaces compared in a contrast configuration show the classical simultaneous lightness contrast effect, while two gray surfaces placed in an assimilation configuration undergo an assimilation effect. However, in the second part of the demonstration, when the displays of contrast are compared to those of assimilation, the gray target surrounded by white in the contrast situation is perceived more similar to the gray target induced by white elements in the assimilation situation and vice versa. Kanizsa explained the paradox by stating that lightness and brightness are confounded. Purpose. The aim of the research was to see which part of the paradox demonstration is responsible for the self-contradiction. To do this, the patterns involved in the Kanizsa's paradox have been measured separately on the continuum of lightness under controlled conditions. Method. The experimental displays were derived from Helson's contrast and assimilation configurations. A new type of measure has been used, since the Munsell scale was placed on a background having the same intensity as the target regions. Observers had to perform a lightness match. A 2×2 experimental design has been used: Direction of physical contrast (increments or decrements); Physical contrast (high or low luminance of the inducers). Results. Assimilation configurations show an effect of contrast for increments and no effect for decrements, while contrast configurations show an effect of contrast for both increments and decrements. Conclusions. When observers are forced to make a lightness match, contrast is observed also in the assimilation displays. Therefore, in the Kanizsa's paradox the assimilation effect seems to be responsible for the self-contradiction.

Agostini, T., Daris, D., Galmonte, A.(2001). Kanizsa's paradox revisited [Abstract]. Journal of Vision, 1( 3): 424, 424a,, doi:10.1167/1.3.424. [CrossRef]
 Supported by MURST Grant n. MM11197484.

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