Nine‐month‐old infants were presented with an engaging and challenging task of visually tracking and reaching for a rolling ball that disappeared and reappeared from behind an occluder. On some trials, the infant observed the experimenter place a barrier on the ball's track; the barrier remained partially visible above the occluder throughout the remainder of the trial. When the task involved only predictive tracking, infants' anticipatory gaze shifts were faster when no barrier was present. When the task involved both tracking and reaching, there were more reaches when no barrier was present. If the infant reached, the timing and extension of the reach and the accompanying gaze shift did not differ with regard to the barrier. Because catching the ball was quite difficult for these infants, task demands interfered with the integration of visual information and visuospatial reasoning about the barrier with the reaching action.

Adults combine different local motions to form a global percept of motion. This study explores the origins of this process by testing how perturbations of local motion influence infants' sensitivity to global motion. Infants at 6-, 12-, and 18-weeks of age viewed random dots moving with a gaussian distribution of dot directions defined by a mean of 0 degree (rightward) or 180 degrees (leftward) and a standard deviation (SD) of 0, 34, or 68 degrees. A well-practiced observer used infants' optokinetic responses to judge the direction of stimulus motion. Infants were studied both cross-sectionally and longitudinally. Direction discrimination was relatively high at all ages when the SD was 0 degree. When the SD was 34 or 68 degrees, performance declined with age. Adult performance was nearly perfect at these SDs. A similar developmental pattern was found with distributions of dot speed. The decline in infant performance is consistent with the development of both neural tuning and receptive field size. The subsequent improvement by adulthood suggests the development of additional processes such as long-range interactions.