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Abigail Huang, Megha Shah, Alice Hon, Eric Altschuler; Perception Begets Reality: A “Contrast-Contrast” Koffka Effect. Journal of Vision 2010;10(7):429. doi: 10.1167/10.7.429.
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© ARVO (1962-2015); The Authors (2016-present)
Eighty years ago Koffka described a fascinating effect: When a contiguous gray ring is placed on a background half of one shade of gray (different from the ring) and half of another shade of gray,the ring appears to be homogeneous. However, if the ring is slightly divided, the two halves of the ring appear different shades of gray with the half of the ring on the darker background appearing lighter than the half of the ring on the lighter background. The Gestalt principle of continuity is invoked to explain this effect with the geometric continuity when the half rings are joined leading to the perception of a homogeneity of shade/color of the ring. In studying this effect we have found a “contrast-contrast” Koffka effect: Single, identical small gray square checks are placed on each of two identical gray half-rings. The half-rings are then placed on a white/light background and a dark/black background, respectively. Both the check on the half-ring on the white background, and the half-ring on the white background appear darker than the check and half-ring, respectively, on the black background--a standard contrast effect. We then join the half rings. The ring now appears homogeneous-Koffka's effect. What about the two checks? They still appear somewhat different with the check on the side of the white background appearing darker. But the difference in the appearance of the checks is less pronounced than when the half-rings were separated! The change in the perception of the half-rings by the Koffka effect has begot a change in the appearance of the checks! We find this a particularly clear demonstration of how perception can influence perception indeed “reality”, with different a perception of the ring begetting a new reality of the perception of the checks.
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