Abstract

A stationary 100% contrast counterphase flickering grating can also be described as two identical 50% contrast components moving in opposite directions. Since infants have a temporal→ nasal (T–N) OKN bias, we wondered whether they would show T–N OKN to counterphase gratings. Two-month-old infants monocularly viewed 48 × 48° counterphase grating (0.17 cycles/degree, 6 Hz, or 0.45 cycles/degree, 6.7 Hz). The ratio of contrasts of the two grating components was varied, with a constant sum of 100%. The direction of OKN was judged by an adult observer on each trial. All infants tested showed predominantly T–N OKN in response to the 50% T–N, 50% N–T grating. On the average, contracts of ~25% T–N, 75% N–T were required to null the OKN response. These results suggest that the infant’s visual system analyzes the counterphase grating into its two opposite motion components, and reduces the effective contrast of the N–T component prior to the site of generation of OKN.

© 1991 Optical Society of America