Scotopic vision, color vision, and stereopsis in infants

Infants as young as 1 month postnatal have scotopic spectral sensitivity closely resembling the CIE standard curve and thus appear to have a functional, rhodopsin-based rod system. Neutrally adapted photopic spectral sensitivities are broad and roughly equal to those of adults tested under similar conditions, although infants may show an elevated sensitivity in the short-wavelength region of the spectrum. Spectral sensitivity has been shown to change with changes in chromatic adaptation. Some wavelength discriminations are possible under conditions in which brightness artifacts can be ruled out. All of these factors support the conclusion that young infants are at least dichromats. However, 2-month-olds to date have shown some unpredicted failures of chromatic discrimination (for example, yellow-greens from white), and the percentage of infants who demonstrate discriminations (for example, among wavelengths greater than or equal to 550 nm) improves with age in early infancy. Thus the status of young infants as trichromats is not yet clearly established. Stereopsis develops rapidly during months 3 to 7, and stereoacuities as good as 1' have been reported by 5 months postnatal. In summary, a variety of visual capabilities can now be measured in infants. Infants' visual capacities are rather surprisingly well established shortly after birth and undergo clear improvements during the first few postnatal months. The interpretation of developmental data and their bearing on visual theory are discussed.