PERCEPTION-ACTION COUPLING IN THE DEVELOPMENT OF VISUAL CONTROL OF POSTURE

In this investigation of developmental changes in the coordination of perceived optical flow and postural responses, 4 age groups of infants (5-, 7-, 9-, and 13-month-olds) were tested while seated on a force p late in a ''moving room.'' During each trial the walls oscillated in a n anteroposterior direction for 12 s, and the postural sway of the inf ant was measured. The results revealed that infants perceived the freq uency and amplitude of the optical flow and scaled their postural resp onses to the visual information. This scaling was present even before infants could sit without support, but it showed considerable improvem ent during the period when infants learn to sit. Taken together, these results suggest that the visuomotor coordination necessary for contro lling sitting is functional prior to the onset of independent sitting but becomes more finely tuned with experience.