Eye movement-based measures of development of spatial contrast sensitivity in infants

This study presents spatial contrast sensitivity functions from 66 infants ranging in age from 12 to 146 days. Functions were derived using a behavioral method based on eye movements; in this method, the subject viewed drifting sinusoidal gratings while an experimenter, who did not know the direction of stimulus drift, voted on that direction based only on the record of the subject's eye movements. Results show that there is a marked increase in contrast sensitivity across age, as well as a modest shift of the peak of the function and of the acuity limit to higher spatial frequencies. However, when normalized with respect to peak frequency and peak sensitivity, the functions at all ages have the same general shape and can be fit with a standard template curve used to describe contrast sensitivity in the adult visual system; that is, even the youngest infants clearly show a drop in sensitivity at frequencies below the peaks of their functions.