Sensitivity
to Light and Color
Light
Light
sensitivity is lower among infants than adults. At 1 month,
an infants light detection threshold is about 50 times greater
that that of an adult; by 3 months, their threshold decreases
so that it is only 10 times higher that an adult's. The increase
in sensitivity appears to be due to the increased length of
the photoreceptors.
Color
Vision
Although
the ability to discriminate different colors is not fully
developed at birth, infants' sensitivity profile for different
wavelengths is similar to that of adults. Their sensitivity
is greatest to intermediate wavelengths (yellow/green) and
less for short (blue) and long (red) wavelengths. At 1 week,
infants are able to discriminate long (e.g. reds, oranges)
and medium wavelengths (e.g. yellows, greens) relatively well.
This presumably reflects the development of the long (L) and
medium (M) wavelength cones. Newborns and even infants as
old as 1 month, however, can have difficulty discriminating
between short (S) wavelengths (e.g. blues). This may be due
to absence of the S cones and associated mechanisms in the
cortex. By 2 months, the S cones of infants are functional,
allowing the infant to better discriminate between short wavelength
colors. By 4 months, infants with normal color vision appear
to categorize color more or less the same way as an adult
with normal trichromatic vision.
An infant's developing color vision abilities can exemplified
using the diagram below. At 1 week, the infant is likely to
perceive the desaturated red (top) to be different from the
uniform gray (both are of same luminance). A difference between
the desaturated blue and uniform gray (bottom) is not likely
to be perceived until about 2 months.
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