Further exploration of human neonatal chromatic-achromatic discrimination.

Newborn (n = 140) and 1-month-old (n = 120) human infants were habituated to achromatic ("white") squares of varying luminance (.35 to 1.16 log cd/m2) and then tested for recovery of habituation with chromatic stimuli from particular spectral locations. Results showed that newborns appear to discriminate 32 degrees yellow-green (dominant lambda = 565 nm) from white, but not 16 degrees or 32 degrees blue (450 nm), 16 degrees blue-green (493 nm), 16 degrees or 32 degrees yellow-green (572 nm), or 16 degrees purple from white. Performance of 1-month-olds was marginally better than that of newborns. Combined with our previous results with the habituation method, these data imply that newborns show little ability to make any chromatic-achromatic discriminations when stimulus size is smaller than 8 degrees, and that even with very large stimuli (e.g. 32 degrees) performance is relatively poor in the blue and yellow-green spectral regions. Although several models were considered, these limitations in the short- and mid-wavelength regions may best be accounted for by the argument that young infants possess general rather than selective immaturities or inefficiencies within their chromatic mechanisms.