Anticipation of Tennis Shot Direction from Whole-body Movement: The role of movement amplitude and dynamics

International audienceWhile recent studies indicate that observers are able to use dynamic information to anticipate whole-body actions like tennis shots, it is less clear whether the action's amplitude may also allow for anticipation. We therefore examined the role of movement dynamics and amplitude for the anticipation of tennis shot direction. In a previous study, movement dynamics and amplitude were separated from the kinematics of tennis players' forehand groundstrokes. In the present study, these were manipulated and tennis shots were simulated. Three conditions were created in which shot direction differences were either preserved or removed: Dynamics-Present-Amplitude-Present (DA), Dynamics-Present-Amplitude-Absent (DA), and Dynamics-Absent-Amplitude-Present (DA). Nineteen low-skill and fifteen intermediate-skill tennis players watched the simulated shots and predicted shot direction from movements prior to ball-racket contact only. Percent of correctly predicted shots per condition was measured. On average, both groups' performance was superior when the dynamics were present (the DA and DA conditions) compared to when it was absent (the DA condition). However, the intermediate-skill players performed above chance independent of amplitude differences in shots (i.e., both the DA and DA conditions), whereas the low-skill group only performed above chance when amplitude differences were absent (the DA condition). These results suggest that the movement's dynamics but not their amplitude provides information from which tennis-shot direction can be anticipated. Furthermore, the successful extraction of dynamical information may be hampered by amplitude differences in a skill dependent manner

Identifying the mechanisms underpinning recognition of structured sequences of action

© 2012 The Experimental Psychology SocietyWe present three experiments to identify the specific information sources that skilled participants use to make recognition judgements when presented with dynamic, structured stimuli. A group of less skilled participants acted as controls. In all experiments, participants were presented with filmed stimuli containing structured action sequences. In a subsequent recognition phase, participants were presented with new and previously seen stimuli and were required to make judgements as to whether or not each sequence had been presented earlier (or were edited versions of earlier sequences). In Experiment 1, skilled participants demonstrated superior sensitivity in recognition when viewing dynamic clips compared with static images and clips where the frames were presented in a nonsequential, randomized manner, implicating the importance of motion information when identifying familiar or unfamiliar sequences. In Experiment 2, we presented normal and mirror-reversed sequences in order to distort access to absolute motion information. Skilled participants demonstrated superior recognition sensitivity, but no significant differences were observed across viewing conditions, leading to the suggestion that skilled participants are more likely to extract relative rather than absolute motion when making such judgements. In Experiment 3, we manipulated relative motion information by occluding several display features for the duration of each film sequence. A significant decrement in performance was reported when centrally located features were occluded compared to those located in more peripheral positions. Findings indicate that skilled participants are particularly sensitive to relative motion information when attempting to identify familiarity in dynamic, visual displays involving interaction between numerous features

Do-it-yourself shuffling and the number of runs under randomness.

A common class of problem in statistical science is estimating, as a benchmark, the probability of some event under randomness. For example, in a sequence of events in which several outcomes are possible and the length of the sequence and number of outcomes of each type known, the number of runs gives an indication of whether the outcomes are random, clustered, or alternating. This note explains and illustrates a simple method of random shuffling that is often useful. We show how the conditional probability distribution of the number of runs may be derived easily in Stata, thus yielding p-values for testing the null hypothesis that the type of outcome is random. We also compare our direct approach with that using the simulate command

On the dynamic information underlying visual anticipation skill

What information underwrites visual anticipation skill in dynamic sport situations? We examined this question on the premise that the optical information used for anticipation resides in the dynamic motion structures, or modes, that are inherent in the observed kinematic patterns. In Experiment 1, we analyzed whole-body movements involved in tennis shots to different directions and distances by means of principal component analysis. The shots differed in the few modes that captured most of the variance, especially as a function of shot direction. In Experiments 2 and 3, skilled and less skilled tennis players were asked to anticipate the direction of simulated shots on the basis of kinematic patterns in which only the constituent dynamic structures were manipulated. The results indicated that players predicted shot direction by picking up the information contained in multiple low-dimensional dynamic modes, suggesting that anticipation skill in tennis entails the extraction of this dynamic information from high-dimensional displays. Copyright 2008 Psychonomic Society, Inc