Sensitivity to second-order motion in 10-month-olds

Ten-month-old infants' sensitivity to first-order motion (FOM) defined by luminance and second-order motion (SOM) defined by flickering was measured in an eye-tracking paradigm. We used a small single disc or gratings moving horizontally. Although infants could track the SOM of a small disc, they failed to exhibit smooth pursuit eye movements. They also failed to track SOM gratings with smooth pursuit. However, the gain of tracking based on slow eye movement was influenced by the motion direction of SOM in cases when both FOM and SOM were presented simultaneously, suggesting some sensitivity to SOM.