Infants' visual tracking of continuous circular motion under conditions of occlusion and non-occlusion

We investigated horizontal and vertical gaze in 9-month-old infants while tracking a fully visible or partly occluded target moving in a circular trajectory. The possibilities for using a corneal-reflection technique (ASL) in such tasks were explored. Data show that horizontal tracking is adult-like at this age over frequencies investigated (0.05-0.4 Hz), vertical tracking is adult-like over the three lowest frequencies, whilst performance deteriorated at 0.4 Hz. During occlusion the rate of successful predictions increased with increasing durations of occlusion, from 250 to 5,000 ms. The latency time before making a predictive move towards the other side of the occluder also increased with duration of occlusion. These predictions are not based on a simple application of inertia but based on more complex non-linear extrapolations. (C) 2002 Elsevier Science Inc. All rights reserved.