VELOCITY THRESHOLDS IN HUMAN INFANTS - IMPLICATIONS FOR THE PERCEPTION OF MOTION

Infants' perception of the direction and speed of motion could be mediated by several underlying mechanisms, including sensitivity to temporal variations in luminance, the relative position of pattern elements, or time-locked spatial displacements. Velocity thresholds were estimated in 6- and 12-week-old infants who viewed a set of moving stripes surrounded by sets of stationary stripes. The forced-choice preferential looking technique was used to collect data from infants who were presented with high-contrast stripes of 2 widths moving at several different velocities. Velocity thresholds were approximately 9°/s in the 6-week-olds and 4°/s in the 12-week-olds. Thresholds did not vary with stripe width at either age, suggesting that motion perception in young infants is not based on a simple flicker-sensitive mechanism. Rather, infant velocity thresholds are based either on a position-sensitive or a motion-sensitive mechanism, at least for high-contrast spatial patterns.