The development of light adaptation in human infants

Increment threshold functions were measured from -4.0 to 1.2 log cd/m2 in 7-12-week-old infants using a behavioral forced-choice paradigm. The slopes of the infant functions were considerably shallower than the slopes of adult functions over the same luminance range. The value of the infant slope increased rapidly between 7 and 12 weeks postnatally. A number of explanations for this developmental shift are considered. It is concluded that changes with age in either spatial summation or intensity-response function gain could cause the increase in slope.