Two-year-olds' search strategies and visual tracking in a hidden displacement task.

Children younger than 3 years have difficulty with search tasks that involve hidden displacement. Partial visual information was provided about a ball's path as it moved toward a hiding place. Children (2.0 and 2.5 years old) saw a ball rolling down a ramp placed behind a transparent screen with 4 opaque doors. A wall, placed on the ramp and directly behind 1 of the doors, protruded above the screen and stopped the ball. Children were asked to find the ball. The transparency of the screen permitted visual tracking of the ball between the doors, but its final resting place was obscured. Both age groups were equally proficient at tracking the ball as it rolled behind the screen, but the 2.5-year-olds were more likely to reach to the correct door. Looking behavior was related to errors in the younger group in that tracking that stopped short or continued past the correct door was associated with incorrect choices.