TIME-TO-CONTACT JUDGMENT IN THE LOCOMOTION OF ADULTS AND PRESCHOOL-CHILDREN

The hypothesis of Lee (1976)-that approach and deceleration toward a s urface can be controlled through the rate of change of the optic varia ble tau-was examined for natural human locomotion. In Experiment 1, 12 adults were asked to perform locomotor tasks that required running at speed and then decelerating so that either the hand or head made a co ntrolled contact with a door. In Experiment 2, 12 preschool children p erformed a relay-running task that required similar control. In Experi ment 3, 12 children and 12 adults ran with a stick as an extension to their arm length and performed the same task. The results supported Le e's hypothesis for the initial phase of approach, but subjects switche d to a separate adjustment phase 2 to 3 arm lengths from the target. C hildren did not adopt an appropriate tau strategy for collision avoida nce and appeared unable to modify their approach strategy to allow for a hand-held stick.