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 thirty-two 4-
month-old and thirty-two 6-month-old infants (mainly Caucasian-White) tracking horizontal, vertical, and
oblique trajectories. Infants tracked oblique trajectories less accurately, but 6-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.