Visual perception for basketball shooting

Vision is one of the six sensory systems that we use to know and interact with our environment but has been singled out as the most important form of exteroception for motor control. The reason for this implicit upgrade is probably that many human actions are directed at objects or targets beyond our immediate physical contact. The only link between these objects and us is the pattern of light reflected from their surfaces, and yet we identify and act upon them with great ease. No doubt humans make significant strides in establishing appropriate relations between perceptions and actions at early stages of their development. When my nephew Rodrigo was three months old it took him considerable perseverance and a lot of jerky movements to finally grasp the toy my mother was patiently holding and rambling. But once the relations between perceptions and actions are better established, humans can be incredibly skilful at interacting with distant objects even when the constraints imposed on the interaction are severe and a high degree of precision is required. Like many other sportive tasks, basketball shooting is characterised by tight temporal constraints, limited spatial variation, and high accuracy demands. How basketball players manage to consistently throw a ball through the basket, even if severely challenged by their opponents, is a remarkable feat that has occupied scientists for years, and the present work is but another step in understanding the intricate relations between visual perception and action in such a context where few errors are allowed and few are made. The research reported in the present thesis was conducted to uncover the visual basis of basketball shooting. Basketball shooting consists of throwing a ball on a parabolic flight that passes through a metal rim twice the size of the ball at three metres height. Common shooting types are the free throw and the jump shot. Free throws are taken in less than 10 s from the 4.6 m line without opposition. Jump shots can be taken from anywhere in the field, usually in the presence of opponents, and imply that the ball is released while the player is airborne. Conventional knowledge stipulates that players must see the basket before they shoot. Straightforward as this statement may seem, it can be incorrect in two ways. First, it is not granted that vision is required before the shot, as opposed to during the shot. While vision gathered before the movement may be useful, it may also be insufficient or unnecessary for accurate shooting. This temporal aspect is relevant because it gives insight into the timely interaction between visual perception and action. Second, it is not certain that the player must actually see the basket, as opposed to merely looking at it. The location of the target may be perceived through various information sources, not necessarily retinal ones. This spatial aspect is relevant because it gives insight into the optical basis of goal-directed movement. In what follows we describe in more detail what these temporal and spatial aspects of visual perception andaction consist of, backed up with relevant literature. Next, we briefly review the available literature on the visual perception of basketball shooting and introduce six experiments in which the temporal and spatial aspects of basketball shooting are investigated.