Abstract

Spatial contrast sensitivity functions (CSFs) were obtained from a large sample of infants grouped in 1-month intervals from 1 to 6 months. Only infants who passed a photorefractive screening were included in the study. The response measure was derived from the infants’ eye movements recorded by an infrared, TV-based eye tracker. Infants viewed vertical sinusoidal gratings, drifting horizontally at 7 deg/s across a large (38 × 29 deg) oscilloscope screen; direction of movement (left or right) was randomized. The output of the eye tracker was presented in real time to a blind experimenter who voted on the direction of grating movement based on the infant’s eye movements; for any grating, contrast was reduced until the experimenter made an error. With these methods, good estimates of threshold can be obtained for 3–6 spatial frequencies in <20 min. The mean infants’ CSFs, at all ages, show considerably greater sensitivity than data previously reported from other behavioral techniques. At all ages, the CSFs are maximal at some intermediate spatial frequency; with increasing age there is a tendency for this maximum to shift to higher frequencies. There is also an overall increase in sensitivity with age, particularly at higher frequencies. By 6 months, the CSF is still below that of adults tested in the same fashion. The behavioral procedures were validated using adult observers who also provided CSFs measured with more traditional psychophysical techniques. From these control experiments, infants’ higher sensitivities with this method can be attributed in part to the use of a large screen and drifting gratings viewed centrally.)

© 1986 Optical Society of America