Observers experience complex patterns of visual motion in daily life due to their own movements through space, the movement of objects, and the geometry of surfaces in the visible world. Motion information shapes behavior and brain activity beginning in infancy. And yet most prior behavioral research has focused on how children process only one…

Watch any crowded intersection, and you will see how adept people are at reading the subtle movements of one another. While adults can readily discriminate small differences in the direction of a moving person, it is unclear if this sensitivity is in place early in development. Here, we present evidence that 4-year-old children are sensitive to…