Spatial frequency tuned covariance channels for red-green and luminance-modulated gratings: psychophysical data from human infants

This study concerns the spatial-frequency-tuned channels underlying:infants ' contrast sensitivity functions (CSFs) for red-green chromatic stimuli, an d their relationship to the channels underlying infants' CSFs for luminance -modulated stimuli. Behavioral (forced-choice preferential-looking) techniq ues and stationary stimuli were used. In experiment 1, contrast thresholds were measured in 4- and 6-month-olds, using isoluminant red-green gratings with spatial frequencies ranging from 0.27 to 1.53 c/deg. In experiment 2, contrast thresholds were measured in 4-month-olds, using both red-green and luminance-modulated gratings in the same low spatial frequency range. Cova riance analyses of individual differences were performed. Experiment 1 reve aled one dominant covariance channel for the detection of red-green grating s, with a second channel contributing to detection of the highest spatial f requencies used. Experiment 2 revealed two to three channels serving color and luminance; but surprisingly these channels:were not statistically separ able for luminance versus chromatic stimuli. Thus, covariance channels for color and luminance that are independent for adults [Peterzell & Teller (20 00). Spatial frequency tuned covariance channels for red-green and luminanc e-modulated gratings: psychophysical data from human adults. Vision Researc h, 40, 417-430] are apparently interdependent in infants. These data sugges t that for infants, defection thresholds for chromatic and luminance-modula ted stimuli may be limited by common mechanisms. (C) 2000 Elsevier science Ltd. All rights reserved.