Newborn's discrimination among mid- and long-wavelength stimuli.

Recent anatomical and behavioral evidence suggests that important visual functions like color vision may be severely limited at birth. Therefore, we examined human newborns' ability to discriminate among stimuli of different wavelength by habituating them to a 16 degrees chromatic square of widely varying luminance (as wide as 1.1 log cd/m2) and then testing for recovery of habituation to a different chromatic square of the same size. In the first experiment, newborns showed evidence of recovery to a 650-nm (peak wavelength) red square after habituating to 545-nm green squares, but they did not recover to the red or the green after habituating to 585-nm yellow squares. In a second experiment using the same procedure, newborns did not show evidence of discriminating the 650-nm red from the 545-nm green when the stimulus size was reduced to 8 degrees. These data suggest that human newborns are capable of making a chromatic discrimination within the spectral region above 540 nm (the Rayleigh region) but their ability is limited to chromatic stimuli of very wide spectral separation and of very large size. Possible neurological bases underlying this immaturity are discussed.