DETECTION OF RELATIVE MOTION BY HUMAN INFANTS

Two experiments were conducted on the detection of relative motion by 8- and 20-week-old infants. In Experiment 1, three types of displays were used: a single target moving with respect to a set of surrounding static reference features, a static target surrounded by a set of reference features with common motion, and a target and surrounding reference features moving in opposite directions. Evidence was found for the detection by 8-week-olds of a single moving bar or of a bar and surround moving in opposite directions. Stronger evidence was found in infants 20 weeks of age. In Experiment 2, 20-week-olds detected the relative motion between a target and a surround moving in the same direction only when the target moved faster than the surround. The results suggest continued development of relative motion mechanisms between 8 and 20 weeks of age.