A scaling analysis of the snake lightness illusion.

Full Abstract

Logvinenko and Maloney (2006) measured perceived dissimilarities between achromatic surfaces placed in two scenes illuminated by neutral lights that could differ in intensity. Using a novel scaling method, they found that dissimilarities between light surface pairs could be represented as a weighted linear combination of two dimensions, "surface lightness" (a perceptual correlate of the difference in the logarithm of surface albedo) and "surface brightness" (which corresponded to the differences of the logarithms of light intensity across the scenes). Here we attempt to measure the contributions of these dimensions to a compelling lightness illusion (the "snake illusion"). It is commonly assumed that this illusion is a result of erroneous segmentation of the snake pattern into regions of unequal illumination. We find that the illusory shift in the snake pattern occurs along the surface lightness dimension, with no contribution from surface brightness. Thus, even if an erroneous segmentation of the snake pattern into strips of unequal illumination does happen, it reveals itself, paradoxically, as illusory changes in surface lightness rather than as surface brightness. We conjecture that the illusion strength depends on the balance between two groups of illumination cues signaling the true (uniform) illumination and the pictorial (uneven) illumination.

Learn Faster Today Improve your study skills

Author information

Author/s: Logvinenko, Alexander D (AD); Petrini, Karin (K); Maloney, Laurence T (LT);

Affiliation: Department of Vision Sciences, Glasgow Caledonian University, Glasgow, Scotland. a.logvinenko(-atsign-)gcal.ac.uk

Grants: EY08226 (Agency:United States NEI)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Perception & psychophysics (Percept Psychophys), published in United States. (Language: eng)

Reference: 2008-Jul; vol 70 (issue 5) : pp 828-40

Dates: Created 2008/07/10; Completed 2008/08/12;

PMID: 18613631, status: MEDLINE (last retrieval date: 11/6/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article (including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MESH Headings shown below.

These are the highest related articles currently in the database:

Effects of contour proximity and lightness on Delboeuf illusions created by circumscribed letters. 30 Jul 2007
Occlusion, transparency, and lightness. 16 Oct 2007
Image segmentation and lightness perception. Mar 2005
Anchoring versus spatial filtering accounts of simultaneous lightness contrast. 12 Sep 2007
A neural model of surface perception: lightness, anchoring, and filling-in. 30 Dec 2005
What are lightness illusions and why do we see them? 30 Aug 2007
Lightness and perceptual transparency. 30 Dec 2005
Gating of remote effects on lightness. 27 Feb 2008
Lightness, illumination, and gradients. 30 Dec 2005
Colours in black and white: the depiction of lightness and brightness in achromatic engravings before the invention of photography. 30 Dec 2005

See 100+ related articles.