Shedding some light on catching in the dark: Perceptual mechanisms for catching fly balls

To catch a lofted ball, a catcher must pick up information that guides loco motion to where the ball will land. The acceleration of tangent of the elev ation angle of the ball (AT) has received empirical support as a possible s ource of this information. Little, however, has been said about how the inf ormation is detected. Do catchers fixate on a stationary point, or do they track the ball with their gaze? Experiment 1 revealed that catchers use eye and head movements to track the ball. This means that if AT is picked up r etinally, it must be done by means of background motion. Alternatively AT c ould be picked up by extraretinal mechanisms, such as the vestibular and pr oprioceptive systems. in Experiment 2, catchers reliably ran to intercept l uminous By balls in the dark, that is, in absence of a visual background, u nder both binocular and monocular viewing conditions. This indicates that t he optical information is not detected by a retinal mechanism alone.