Infant luminance and chromatic contrast sensitivity: optokinetic nystagmus data on 3-month-olds.

Infant color vision is poor, and most psychophysical experiments agree that infant color vision emerges between ages 3 weeks and 3 months. Presumably, the color vision of infants is poor during the months immediately after it has emerged. We have tested two alternative explanations for the poor color vision of infants: (1) there is a special critical immaturity within the color pathways of infants; (2) infants have poor infant color vision because they are insensitive to contrast. Luminance and chromatic contrast thresholds were measured on 3-month-olds using optokinetic nystagmus (OKN), and adult luminance and chromatic contrast thresholds were measured using OKN and two forced-choice methods: direction-of-motion discrimination and grating detection. The infant chromatic-to-luminance contrast threshold ratio shows that infants are as sensitive or even more sensitive than adults to color, depending on the testing method used on adults. This result suggests that the general contrast insensitivity hypothesis is correct. Conservative "worst-case" quantitative analysis strongly suggests that this result is not the consequence of a luminance artifact.