Information processing and constraints-based views of skill acquisition: divergent or complementary?
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Aptitude↗
Biomedical subjects
Keith Davids
Publications and source records attributed to Keith Davids.
Postural stability and hand preference as constraints on one-handed catching performance in children.
Effects of postural state and hand preference as constraints on 1-handed catching performance were investigated in different ability groups of children aged 9-10 years. On the basis of pretest data, the authors classified 48 participants into groups of good, intermediate, and poor catchers (n = 16 in each) and asked them to perform 1-handed catches with their preferred and nonpreferred hands while standing and sitting. The good catchers' performance was not affected by the imposed postural constraints but did improve when they used the preferred hand. A similar effect of hand preference was evident in the intermediate and poor catchers, but there was also an effect of postural constraint. Independent of hand preference, intermediate catchers' performance while seated improved significantly compared with that during standing. For poor catchers, there was an interaction between hand preference and posture; significant improvement was evident only when they used the preferred hand in the sitting condition. The finding that manipulation of posture and hand preference affected performance outcomes indicates that perceptual skill is not the only influence on catching performance in children. Manipulation of those key constraints may facilitate the acquisition of catching skill, but more research is needed to determine the permanence of those effects.
Aptitude↗
Movement models from sports reveal fundamental insights into coordination processes.
Trends for studying coordination and control have shifted from simple movement models toward complex, multijoint actions in sports such as cricket. Use of such movement models exemplifies the nature of interacting constraints that shape emergence of coordination and control processes as proposed by dynamical systems theory and ecological psychology.
Humans↗
Nested task constraints shape continuous perception-action coupling control during human locomotor pointing.
Behavioural studies of human locomotor pointing have been dominated by specific task constraints of generating maximal approach velocity towards spatial targets. To examine locomotor pointing under different nested task constraints, at sub-maximal approach velocities and with concomitant differences in speed-accuracy trade offs, run-ups of professional cricket bowlers (n = 6) were analysed. Inter- and intra-trial analyses of step length adjustments revealed how differences between current and required locomotor pointing behaviour constrained visual adaptations of gait. Results supported a continuous perception-action coupling control mechanism, although no relationship was observed between step number in sequence and total amount of adjustment made, implying that visual adaptations did not continue to the end of a run-up once initiated. Rather, bowlers made step adjustments throughout the run-up, with strong associations for amount of adjustment made and amount needed. Significant variations were observed in inter-individual strategies for making most adjustments at different points of the run-up. A key premise of prospective control models of locomotor pointing was found to be robust, since regulation of cricketer's gait was continuous and based on perception of current and required behaviour. Findings extend understanding of the nature and range of nested task constraints under which perception-action coupling controls locomotor pointing performance.
Adaptation, Physiological↗
Object rotation effects on the timing of a hitting action.
We investigated how perturbing optical information affects the guidance of an unfolding hitting action. Using monocular and binocular vision, six participants were required to hit a rectangular foam object, released from two different heights, under four different approach conditions, two with object rotation (to perturb the viewed surface area) and two without. Participants made more misses under monocular conditions, and the presence of rotation had a significant effect on the duration between the arm's peak velocity and its contact with the object. We conclude that binocular information contributes to the timing of interceptive tasks. In addition, the guidance of interceptive actions does not appear to be based solely on object expansion information picked up from the viewed surface area.
Adult↗
Movement systems as dynamical systems: the functional role of variability and its implications for sports medicine.
In recent years, concepts and tools from dynamical systems theory have been successfully applied to the study of movement systems, contradicting traditional views of variability as noise or error. From this perspective, it is apparent that variability in movement systems is omnipresent and unavoidable due to the distinct constraints that shape each individual's behaviour. In this position paper, it is argued that trial-to-trial movement variations within individuals and performance differences observed between individuals may be best interpreted as attempts to exploit the variability that is inherent within and between biological systems. That is, variability in movement systems helps individuals adapt to the unique constraints (personal, task and environmental) impinging on them across different timescales. We examine the implications of these ideas for sports medicine, by: (i) focusing on intra-individual variability in postural control to exemplify within-individual real-time adaptations to changing informational constraints in the performance environment; and (ii) interpreting recent evidence on the role of the angiotensin-converting enzyme gene as a genetic (developmental) constraint on individual differences in physical performance. The implementation of a dynamical systems theoretical interpretation of variability in movement systems signals a need to re-evaluate the ubiquitous influence of the traditional 'medical model' in interpreting motor behaviour and performance constrained by disease or injury to the movement system. Accordingly, there is a need to develop new tools for providing individualised plots of motor behaviour and performance as a function of key constraints. Coordination profiling is proposed as one such alternative approach for interpreting the variability and stability demonstrated by individuals as they attempt to construct functional, goal-directed patterns of motor behaviour during each unique performance. Finally, the relative contribution of genes and training to between-individual performance variation is highlighted, with the conclusion that dynamical systems theory provides an appropriate multidisciplinary theoretical framework to explain their interaction in supporting physical performance.
Adaptation, Physiological↗
Anticipatory responses to perturbation of co-ordination in one-handed catching.
Anticipatory responses to perturbation have rarely been studied in the co-ordination of dynamic interceptive actions. In this study, the kinematics of ball catching were examined in skilled catchers when mechanical perturbation of the catching arm was expected and unexpected. During trials where the perturbation was anticipated, participants initiated movements earlier (207 +/- 32 ms) than in randomly perturbed trials (223 +/- 34 ms). Furthermore, several individuals also tended to move their hand faster when perturbations were expected compared to baseline trials. Individual analyses revealed that three out of eight participants exhibited changes in the relative timing of the grasp phase to adapt to the specific manipulation of task constraints. Anticipatory responses were revealed in changes not only at movement initiation but also in the resulting adaptations to the co-ordination of reach and grasp phases of ball catching. When the catchers could not anticipate perturbations, movement strategies suggested the use of a continuous tracking-based mode of control rather than a prediction-based mode of control.
Adult↗
'Keeping the eye on the ball': the legacy of John Whiting (1929-2001) in sport science.
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History, 20th Century↗
Effect of verbal instructions and image size on visual search strategies in basketball free throw shooting.
We assessed the effects on basketball free throw performance of two types of verbal directions with an external attentional focus. Novices (n = 16) were pre-tested on free throw performance and assigned to two groups of similar ability (n = 8 in each). Both groups received verbal instructions with an external focus on either movement dynamics (movement form) or movement effects (e.g. ball trajectory relative to basket). The participants also observed a skilled model performing the task on either a small or large screen monitor, to ascertain the effects of visual presentation mode on task performance. After observation of six videotaped trials, all participants were given a post-test. Visual search patterns were monitored during observation and cross-referenced with performance on the pre- and post-test. Group effects were noted for verbal instructions and image size on visual search strategies and free throw performance. The 'movement effects' group saw a significant improvement in outcome scores between the pre-test and post-test. These results supported evidence that this group spent more viewing time on information outside the body than the 'movement dynamics' group. Image size affected both groups equally with more fixations of shorter duration when viewing the small screen. The results support the benefits of instructions when observing a model with an external focus on movement effects, not dynamics.
Adult↗
Interacting Constraints and the Emergence of Postural Behavior in ACL-Deficient Subjects.
In this study, the authors examined how task, informational, and sensorimotor system constraints influence postural control. Postural behavior of subjects with (n = 15) and without (n = 15) a key sensorimotor system constraint, anterior cruciate ligaments (ACLs) in 1 knee, was examined during 1- and 2-legged stance with and without vision. Postural control was assessed on a commonly used postural sway meter and on a dynamic stabilometer. Data on postural sway characteristics were obtained for 30 s under 6 different conditions: standing, with eyes open and closed, on both legs, on the injured leg, and on the noninjured leg. The interaction of task, informational, and sensorimotor constraints was observed only on the dynamic stabilometer and not the postural sway meter. Vision was the most important informational constraint on postural control for subjects on the dynamic stabilometer, particularly for the ACL-deficient group standing on the injured leg. Under more static task constraints, ACL deficiency did not prove a significant disadvantage, because vision was confirmed as a significant source of exproprioceptive information. The results support the functionality of using dynamic tasks such as a stabilometer in assessing postural behavior of subjects with sensorimotor system constraints.
Journal Article↗
Structural Organization of Practice: Effects of Practicing Under Different Informational Constraints on the Acquisition of One-Handed Catching Skill.
The question addressed in this study was the effects of the manipulation of the informational constraints of practice conditions on the acquisition of one-handed catching skill. Three groups of poor catchers (8 participants per group) practiced in either a normal-light, ball-only, or interspersed ball-only and normal-light condition (N = 450 trials). All groups exhibited a significant improvement in the number of catches and catching score and a reduction in the number of misses by the end of practice. The structural organization of the practice conditions had a significant effect on catching performance. Practicing in the interspersed condition had a positive residual effect on subjects' performance in normal light. Similarly, there was a positive residual effect of practicing in the ball-only and the interspersed conditions on subjects' normal-light, posttest performance. The findings are interpreted as support for the argument that practicing under varying informational constraints can benefit skill acquisition by directing the subjects' search toward relevant sources of information.
Journal Article↗