Expertise and the perception of kinematic and situational probability information

Two experiments were conducted on the nature of expert perception in the sp ort of squash. In the first experiment, ten expert and fifteen novice playe rs attempted to predict the direction and force of squash strokes from eith er a film display (occluded at variable time periods before and after the o pposing player had struck the hall) or a matched point-light display (conta ining only the basic kinematic features of the opponent's movement pattern) . Experts outperformed the novices under both display conditions, and the s ame basic time windows that characterised expert and novice pick-up of info rmation in the film task also persisted in the point-light task. This sugge sts that the experts' perceptual advantage is directly related to their sup erior pick-up of essential kinematic information. In the second experiment, the vision of six expert and six less skilled players was occluded by remo tely triggered liquid-crystal spectacles at quasi-random intervals during s imulated match play. Players were required to complete their current stroke even when the display was occluded and their prediction performance was as sessed with respect to whether they moved to the correct half of the court to match the direction and depth of the opponent's stroke. Consistent with experiment 1, experts were found to be superior in their advance pick-up of both directional and depth information when the display was occluded durin g the opponent's hitting action. However, experts also remained better than chance, and clearly superior to less skilled players, in their prediction performance under conditions where occlusion occurred before any significan t pre-contact preparatory movement by the opposing player was visible. This additional source of expert superiority is attributable to their superior attunement to the information contained in the situational probabilities an d sequential dependences within their opponent's pattern of play.