Vision Sciences Society 2005
Volume 5, Number 8, Abstract 1027, Page 1027a doi:10.1167/5.8.1027 http://journalofvision.org/5/8/1027/ ISSN 1534-7362

Expansive and contractive size perception with color patches


Miwa Nakano Graduate School of Frontier Biosciences, Osaka University, Japan
Seiji Tanabe Graduate School of Frontier Biosciences, Osaka University, Japan
Yoshiya Mori Graduate School of Frontier Biosciences, Osaka University, Japan
Bungo Ikegami School of Engineering Science, Osaka University, Japan
Ichiro Fujita Graduate School of Frontier Biosciences, Osaka University, Japan

Abstract

Empirically, changing the color of an object modulates its perceived size; e.g., clothes in a particular color make you look thinner. In order to quantify this effect, we systematically examined the effects of object and background color on size perception. Subjects viewed a pair of solid square patches on a computer display and were instructed to report which patch subjectively appeared larger. The color and size of one of the two patches were varied (test patch), while those of the other patch were constant (sample patch). The effect of isoluminant colors of the test patch on its perceived size was assessed as a shift in the psychometric function in which the percentage of trials perceiving the test patch as larger was plotted against the actual size of the test patch. The psychometric functions for some isoluminant colors were shifted in either direction along the abscissa, indicating that patches with some particular colors expanded or contracted in perceived size. The colors with expansive or contractive effects were consistent across subjects. The results indicate that chromaticity (hue and saturation) of the stimulus affected size perception. To determine whether perceived size depends on the background color, we tested various combinations of patch and background colors. Larger chromatic contrasts between the patch and background resulted in larger size percepts, while smaller chromatic contrasts led to smaller size percepts. As in the isoluminant test, larger luminance contrasts between the test patch and background resulted in larger size percepts. Our results suggest that the chromatic and luminance contrasts between the patch and its background, rather than the chromaticity and luminance of the patch itself, determine the perceived size. The neural mechanism modulating perceived size might involve cortical neurons that modulate their size tuning with chromatic and luminance contrast (Solomon et al. 2004; Sceniak et al. 1999).