JOURNAL OF EXPERIMENTAL CHILD PSYCHOLOGY 40, 528-547 (1985) The Development of Contrast Constancy BENJAMIN R. STEPHENS Williams College AND MARTIN S. BANKS University of California, Berkeley The mature visual system possesses mechanisms that enable invariant perception of the contrast of an object and its features as the object undergoes changes in distance. This phenomenon, which has been called contrast constancy, obtains at suprathreshold contrasts only. Some models of contrast constancy assume the presence of narrowband spatial-frequency channels. An implication of M. S. Banks, B. R. Stephens, and E. E. Hartmann (1985, Journal of Experimental Child Psychology, 40,501-527) is that contrast constancy should not be observed at 6 weeks but may be observed at 12 weeks. We examined this implication by investigating the development of contrast constancy in 6- and 12-week-old infants. Two sine wave gratings, differing in spatial frequency by a factor of 3, were presented side-by-side. The contrast of one grating was varied in order to estimate the contrast at which preference for the two gratings was equal. The equal preference points for 6-week-olds were predictable from their contrast thresholds. The lZweek-olds’ equal preference points for low-contrast stimuli were predictable from their contrast thresholds, but those for intermediate and high-contrast stimuli were not. Thus, if one accepts the assumption that equal preference in infants is analogous to apparent contrast matches in adults, these data imply that contrast constancy is observed at 12 weeks but not 6 weeks. The perceptual consequences of this developmental transition are discussed. o 1985 Academic press. IN. One of the most sophisticated and important visual functions is the ability to recognize and identify objects on the basis of pattern information. This research was supported by NIH Research Grant HD-12572 and by NIMH Research Scientist Development Award MH-00318 to M.S.B. It is based, in part, on a thesis presented to the University of Texas at Austin by Benjamin R. Stephens in partial fulfillment of the requirements for the doctoral degree. The authors thank Alice Andrews and Mark Viator for assisting in subject recruitment and data collection. Send reprint requests to Benjamin R. Stephens, Department of Psychology, Bronfman Science Center, Williams College, Williamstown, MA 01267. 528 0022-0965/85 $3.00 Copyright 0 1985 by Academic Press, Inc. All rights of reproduction in any form reserved.