Scotopic sensitivity of the two-month-old human infant.

The 2-month-old human infant is known to be less visually sensitive than the adult by a factor of 50, if sensitivity is measured by the threshold for detecting a test light in the dark. In the present experiment, visual sensitivity of infants and adults did not differ significantly when sensitivity was measured by the ability of an adapting light to elevate test threshold. This result suggests that the infants' insensitivity to test flashes is due to immaturities proximal to the site of light adaptation, while the more distal stages of visual processing, including the adaptation process itself, are relatively mature at that age.