Hubert Ripoll

Effect of expertise on coincident-timing accuracy in a fast ball game

The aim of this study was to examine the effect of intensive practice in table tennis on perceptual coincident timing. The main question was whether the perceptual demands encountered in fast ball sports produce modifications of the perceptual visual system. Expert table tennis players and novices were compared in a perceptual task which consisted of estimating, by pressing a key, the arrival of a moving stimulus at a target. The stimulus, which was presented either at constant velocity or at constant deceleration, reproduced as closely as possible the natural visual demands encountered in table tennis. The difference between the time of response and the time of arrival of the stimulus at a target position was measured over 40 trials for each of the 16 participants. The results showed no effect of expertise under the constant-velocity condition but an effect under the decelerative condition, indicating that experts were less trajectory-dependent than novices. This result was interpreted as reflecting a better adaptation of the perceptual system of experts to the constraints encountered during table tennis and specifically to the perceptual demands resulting from varied and decelerated ball trajectories. Finally, some limitations of the coincidence anticipation procedure are highlighted, concerning its use in practical settings for evaluating athletes or detecting sport talents, and the need for the simulation conditions during testing to reproduce as closely as possible the perceptual demands of real life is discussed.

Effects of Tennis Practice on the Coincidence Timing Accuracy of Adults and Children

This study examines the development of perceptuomotor processes involved in coincidence timing tasks according to age and experience in tennis. Tennis players and novices, 7, 10, 13, and 23 years of age, were tested in a coincidence timing task which consisted of estimating the arrival of a simulated moving object on a target. The effect of three different motions were analyzed: constant velocity, constant acceleration, and constant deceleration. Results showed that (1) timing accuracy improves mainly between the ages of 7 and 10 years; (2) tennis practice accelerates the development of timing accuracy; and (3) acceleration or deceleration of the moving stimulus had no effect on the timing accuracy of any of the tested groups, suggesting a continuous visual control of the trajectory. Theoretical implications for the development of perceptuomotor processes involved in coincidence timing tasks are discussed.

The regulation of release parameters in underarm precision throwing

The aim of this study was to determine if adults spontaneously exploit the laws of physics to achieve better accuracy when throwing at various distances. Eight adults performed 25 underarm throws at five horizontal circular targets located 4, 5, 6, 7 and 8 m away with a constant 5% relative accuracy requirement. Angle and speed of the ball at release were found to increase with throwing distance, while the coordinates of the release point did not change significantly. These results support the idea that people minimize the variability in impact distance by adapting both the angle and the speed at ball release following a mechanical optimum predicted by the laws of physics. Moreover, variability in distance was found to be less than expected because of independent variations in the angle and speed at ball release. Hence, the control of precision throwing seems to imply compensatory variability, as frequently reported in the control of skilled actions.

Age differences in estimating arrival-time.

The present study examined the accuracy in extrapolating an occluded trajectory in relation to observer age. Adults and children aged 7, 10, and 13 were tested in a prediction-motion task which consisted of judging, after the occlusion of the final part of its path, the moment of arrival of a moving stimulus towards a specified position. Results showed that children as young as 7 years old are able to use the same strategy as adults in the extrapolation of an occluded moving object. However, accuracy in responses improves most significantly for occlusion times equal to or more than 400 ms and this improvement occurs mainly between 7 and 10 years of age. This confirms that children are less efficient in performing the computations necessary to extrapolate in time an occluded trajectory.