Orientation effects in the development of linear object tracking in early infancy

Infants' oculomotor tracking develops rapidly but is poorer when there are horizontal and vertical movement components. Additionally, persistence of objects moving through occlusion emerges at 4 months but initially is absent for objects moving obliquely. In two experiments we recorded eye movements of 32 4-month-old and 32 6-month-old infants (mainly Caucasian-White) tracking horizontal, vertical, and oblique trajectories. Infants tracked oblique trajectories less accurately, but six-month-olds tracked more accurately, such that they tracked oblique trajectories as accurately as 4-month-olds tracked horizontal and vertical trajectories. Similar results emerged when the object was temporarily occluded. Thus, 4-month-olds’ tracking of oblique trajectories may be insufficient to support object persistence, whereas 6-month-olds may track sufficiently accurately to perceive object persistence for all trajectory orientations