Pattern motion integration in infants.

To investigate the development of motion integration in infants, we used an eye movement technique to measure subjects' ability to track leftward versus rightward pattern motion in a stimulus consisting of a field of spatially segregated moving gratings. Each grating moved in one of two oblique directions, with the two directions interleaved across the display. When spatially integrated, pattern motion for these paired component motions was either rightward or leftward. To control for the possibility that horizontal eye movements elicited by this stimulus were due to the horizontal motion vector present in each obliquely moving grating, we also measured responses to a field where every grating moved in the same oblique direction. The difference in performance between the integration stimulus and this control stimulus was taken as a measure of integration. Data from 2-, 3-, 4-, and 5-month-old infants revealed significant motion integration, suggesting that higher order motion areas, such as the middle temporal area (MT) may develop at a relatively early age. In addition, the integration effect decreased consistently and significantly with age (p <.005), suggesting a reduction in the spatial extent of motion integration over the course of development.