Spectral sensitivity and chromatic discriminations in 3- and 7-week-old human infants.

The chromatic discrimination capabilities of 3- and 7-week-old infants were tested using 8 degrees, 417-, 448-, 486-, 540-, and 645-nm test fields embedded in a 547-nm surround and 486-nm test fields in a broadband red surround. In corroboration of earlier studies, few 3-week-old infants demonstrated chromatic discriminations, although their performance was somewhat better when one of the lights was long wavelength. Most 7-week-old infants could make chromatic discriminations, but they still demonstrated performance minima. The radiances of the test lights at the infants' performance minima were used to generate a spectral luminous efficiency curve. This curve agreed with both the adult heterochromatic brightness matches measured at 30 degrees of visual eccentricity in situ and the standard adult scotopic sensitivity curve V(lambda) over the short- and mid-wavelength range but deviated from both adult curves for the 645-nm test stimulus on a 547-nm surround. The results suggest that rod-initiated signals play a major role in infants' visual performance under the conditions tested.