The Journal of Neuroscience, October 1, 1999, 19(19):8542-8551
An Empirical Explanation of the Cornsweet Effect
Dale
Purves,
Amita
Shimpi, and
R. Beau
Lotto
Duke University Medical Center, Durham, North Carolina
27710
A long-standing puzzle in vision is the assignment of
illusory brightness values to visual territories based on the
characteristics of their edges (the Craik-O'Brien-Cornsweet effect).
Here we show that the perception of the equiluminant territories
flanking the Cornsweet edge varies according to whether these regions
are more likely to be similarly illuminated surfaces having the same
material properties or unequally illuminated surfaces with different
properties. Thus, if the likelihood is increased that these territories
are surfaces with similar reflectance properties under the same
illuminant, the Craik-O'Brien-Cornsweet effect is diminished;
conversely, if the likelihood is increased that the adjoining
territories are differently reflective surfaces receiving different
amounts of illumination, the effect is enhanced. These findings
indicate that the Craik-O'Brien-Cornsweet effect is determined by
the relative probabilities of the possible sources of the luminance
profiles in the stimulus.
Key words:
vision; edge effects; illusion; filling in; brightness; luminance; empirical probability
Copyright © 1999 Society for Neuroscience 0270-6474/99/19198542-10$05.00/0