What cues do billiard experts use? Conceptual and perceptual judgments of spin

Complex dynamic events are often misunderstood at the perceptual and intuitive level. In spite of these difficulties, experts, such as athletes or billiard players, learn to make very precise dynamic judgments. This study explored the basis of such judgmental abilities using the example of rotational motions (spin) as they occur in billiards. Five experiments were carried out to evaluate two paradigms that might explain how observers may judge the dynamics of spin: perceptual attunement and learning of procedural heuristics that apply to one salient dimension of information. Conceptual knowledge about the effects of spin on trajectories of billiard balls was found to be erroneous. Almost all novices and more than half of the experts tested had mistaken beliefs about one particular type of spin (english). These beliefs were mirrored in animated contexts where subjects had to observe computer-generated events of spinning balls that had possible and impossible effects. Visual performance was also assessed in an ecological setting. It is concluded that novices are not perceptually attuned to the general dynamics of spin and that experts do not acquire such attunement. The heuristics approach, on the other hand, seems to explain the systematic errors that novices make. However, it thoroughly fails to explain why expert observers are able to judge multi-dimensional with an accuracy that equals the precision with which shots can be executed. Perceptual abilities appear to be more situation-specific than assumed by either of the two approaches. Dynamics of Spin in Billiards 3