Koffka’s Ring Effect Depends on Thickness, Not Continuity
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- University of Medicine & Dentistry of New Jersey, Physical Medicine and Rehabilitation
- University of Medicine & Dentistry of New Jersey, School of Medicine
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This manuscript is a preprint. A published version is available at:
10.1068/p6027 (Peer Reviewed) Published as "Thickness and the Koffka ring effect" Perception 37(9) 1458 – 1460; 2008.- Document Type:
- Manuscript
- Date:
- Received 17 December 2007 06:13 UTC; Posted 17 December 2007
- Subjects:
- Neuroscience
- Abstract:
More than 70 years ago Gestalt psychologist Kurt Koffka described a fascinating effect1,2: When a contiguous grey ring is placed on a background half of one shade of grey (different from the ring) and half of another shade of grey, the ring appears to be a homogenous. However, if the ring is slightly divided, now the two halves of the ring appear different shades of grey with the half of the ring on the darker background appearing lighter than the half of the ring on the darker background. The Gestalt principle of continuity in visual perception is invoked to explain this effect. Here we show that in fact when the ring is made thinner it appears heterogeneous even when contiguous. Furthermore, when viewing a thick ring after first viewing a thin ring, the thick ring now too appears heterogenous! These effects are also demonstrated with a colored background and backgrounds with more than two regions. We show that standard simultaneous brightness and color contrast weaken with larger test patches. Thus, Koffka’s ring effect is due to vanishingly weak simultaneous contrast for a sufficiently thick ring, not continuity.
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Huang, Abigail, Hon, Alice, and Altschuler, Eric. Koffka’s Ring Effect Depends on Thickness, Not Continuity. Available from Nature Precedings <http://hdl.handle.net/10101/npre.2007.1433.1> (2007)
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Published version:
10.1068/p6027 (Peer Reviewed) Published as "Thickness and the Koffka ring effect" Perception 37(9) 1458 – 1460; 2008. -
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Danko Georgiev on 27 April 2008 05:11 UTC
I think the data is interesting concerning the observation that thin ring even if not interrupted, appears to be heterogeneous, BUT the explanation given by the authors is highly dubious for the following reason:
[1] It does NOT remove the effect of discontinuity. Interrupted ring is still “more” heterogeneous, than continuous ring.
[2] The heterogeneous borders of the continuous ring are smeared, while the borders of the interrupted ring are “sharp”.
[3] In thick rings there is NO heterogeneous color even if one looks at the thinner images, or it depends on the thickness of the ring. Too thick cannot be heterogenous, no matter how long you look the thinner rings first.
—- CONCLUSION—
The effect that authors investigate from points [1] – [3] seems to be JUST a manifestation of the LATERAL INHIBITION mechanism in retina, where it makes the borders of a shape sharper. For good reference one can see any internet source on lateral inhibition as explanation of visual illusions e.g.
http://www.michaelbach.de/ot/lum_herGrid/index.html
The mathematics is good starting point, and I think the effect of thin rings, or inseting a white discontinuity are accurately predicted by the lateral inhibition mechanism. The thinner the ring, the closer the two “modified borders”, hence it is more likely that the whole thickness of the ring is with altered colour.
Danko Georgiev, Kanazawa University