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A Mark Williams

Publications and source records attributed to A Mark Williams.

At least 19 recordsLinked to original sources
PubMed2007

End-point focus manipulations to determine what information is used during observational learning.

We required two groups of participants to observe an end-point model (ENDPT) while another two groups viewed a full-body, point-light model (FULL) to determine the role of relative motion information in acquisition of a multi-limb, whole-body action. One ENDPT and one FULL group also bowled a ball. Following retention, all groups observed the FULL model. The participants' movements were compared to the model and outcome attainment was quantified. There was no difference in shoulder-elbow coordination between groups in acquisition or retention. The FULL groups replicated hip-knee coordination more accurately than did ENDPT groups in early acquisition only, with no significant differences in late acquisition or retention. Both bowling groups became more accurate at the task across acquisition, but the ENDPT group was more accurate and consistent in retention. Providing intra-limb relative motion in re-acquisition did not improve coordination for the ENDPT groups, but it did facilitate movement control (peak wrist velocity) and outcome attainment (target accuracy). The acquisition of coordination during observational learning is not only a result of copying relative motion information, but also involves copying of end-point trajectory information from the primary effector.

Adolescent↗
PubMed2006

A comparison of intra- and inter-limb relative motion information in modelling a novel motor skill.

The importance of intra- and inter-limb relative motion in modelling a whole body coordination skill was examined. Participants were assigned to one of four groups: Full-Body point light model of a cricket bowler, INTRA-LIMB relative motion of the bowling arm, INTER-LIMB relative motions of the right and left wrists or NO-Relative motion, showing only the motions of the right wrist. During 60 acquisition trials, participants viewed the model five times before each 10-trial block. Retention was examined the following day. Although all groups improved on intra-limb coordination of the bowling arm, the INTRA-LIMB and FULL-BODY groups were more accurate than the INTER-LIMB group in acquisition, although these groups did not differ in retention. For inter-limb coordination, the three groups who received relative motion information performed more like the model than the NO-Relative motion group (even though the INTRA-LIMB group did not see the other limb). The amount of information within a display plays a constraining role on acquisition, perhaps more so than the type of information, such that the acquisition of coordination is more an emergent feature of observational learning, rather than a direct approximation of the model.

Adult↗
PubMed2006

Scaling a motor skill through observation and practice.

The authors examined the proposal that a motor skill is scaled through physical practice and not through observation of a model. In 4 groups, participants (N = 32) did or did not imitate a model bowling a ball to a target 8 m away. In an assessment phase, those groups did or did not observe the same model bowling a ball to a target 4 m away. Participants who viewed a model in the assessment phase were more accurate and consistent in terms of bowling accuracy than were those who did not. Their shoulder and wrist velocity profiles were more similar to those of the 4-m model than were those of the no-model group. Participants who had previous practice and viewed a demonstration were more accurate at scaling the wrist of the bowling arm. Observing a demonstration facilitates the acquisition of control-related features of a movement. Furthermore, early acquisition of coordination aids the use of velocity information for scaling the endpoint of the primary effector.

Adolescent↗
PubMed2005

An evaluation of the minimal constraining information during observation for movement reproduction.

An important question in the field of imitation is what information is used for movement reproduction. While it is argued that relative motion information is perceived and minimised, direct evidence is lacking. In this experiment relative motion was manipulated to convey a novel kicking action. Twenty-four adults were assigned to one of the three impoverished relative motion display groups showing only the TOE, FOOT or LEG. After practise with partial information, participants watched a full-body display and in a final condition performed the action with an additional context constraint (i.e., a ball). Movement kinematics were collected and difference scores between participants and the model were analysed. The groups did not differ in terms of knee-ankle coordination. For hip-knee, the TOE group performed more like the model than the FOOT and LEG group. When transferred to the full-body display, there were no significant improvements. End-point trajectory information can provide sufficient information to reproduce key characteristics of the movement form.

Adult↗
PubMed2005

Perceptual-cognitive expertise in sport: some considerations when applying the expert performance approach.

The number of researchers studying perceptual-cognitive expertise in sport is increasing. The intention in this paper is to review the currently accepted framework for studying expert performance and to consider implications for undertaking research work in the area of perceptual-cognitive expertise in sport. The expert performance approach presents a descriptive and inductive approach for the systematic study of expert performance. The nature of expert performance is initially captured in the laboratory using representative tasks that identify reliably superior performance. Process-tracing measures are employed to determine the mechanisms that mediate expert performance on the task. Finally, the specific types of activities that lead to the acquisition and development of these mediating mechanisms are identified. General principles and mechanisms may be discovered and then validated by more traditional experimental designs. The relevance of this approach to the study of perceptual-cognitive expertise in sport is discussed and suggestions for future work highlighted.

Attention↗
PubMed2005

Modelling relative motion to facilitate intra-limb coordination.

The importance of relative motion information when modelling a novel motor skill was examined. Participants were assigned to one of four groups. Groups 1 and 2 viewed demonstrations of a skilled cricket bowler presented in either 'video' or 'point light' format. Group 3 observed a single point of light pertaining to the 'wrist' of the skilled bowler only. Participants in Group 4 did not receive a demonstration and acted as controls. During 60 acquisition trials, participants in the demonstration groups viewed a model five times before each 10-trial block. Retention was examined the following day. Intra-limb coordination was assessed for the right elbow relative to the wrist in comparison to the model. The demonstration groups showed greater concordance with the model than the control group. However, the 'wrist' group performed less like the model than the 'point light' and 'video' groups, who did not differ from each other. These effects were maintained in retention. Relative motion information aided the acquisition of intra-limb coordination, while making this information more salient (through point lights) provided no additional benefit. The motion of the model's bowling arm was replicated more closely than the non-bowling arm, suggesting that information from the end-effector is prioritized during observation for later reproduction.

Adult↗
PubMed2005

Visual perception and gaze control in judging versus producing phase relations.

We studied visual perception and gaze control in nine participants while they judged the relative phase between two oscillating stimuli (Experiment 1), and while they moved their hand--and therewith a concurrent feedback signal--in-phase or in antiphase with an oscillating stimulus (Experiment 2). As in previous studies, the mean relative phase judgements in Experiment 1 corresponded to the presented phase relations (0 degree, 45 degrees, 90 degrees, 135 degrees, and 180 degrees), whereas their standard deviations followed an inverted U-function of relative phase. The relative phase judgements were hardly affected by the degree of visibility (fully visible, inner parts occluded, outer parts occluded) and the amplitude (5 degrees, 10 degrees, and 20 degrees) of the stimuli. Stimulus-gaze coupling decreased as relative phase increased, and its variability correlated with that of the relative phase judgements. Taken together, task performance and gaze behaviour suggested that the judgement of relative phase might be flexibly based on different variables, rather than a single variable like relative direction of motion. In Experiment 2, the production of the antiphase relation was less stable than that of the in-phase relation. Performance deteriorated when the outer parts of the signals were occluded and when their amplitudes were reduced. Stimulus-gaze coupling was stronger during in-phase than during antiphase tracking and weaker when the signals were partially occluded and when their amplitudes were reduced. Stimulus-gaze coupling at 0 degrees and 180 degrees was stronger in Experiment 2 than in Experiment 1, suggesting that the visual perception of relative phase may benefit from its active production. Overall, the results clearly indicated that visual perception of relative phase and the corresponding gaze control are strongly task-dependent.

Adult↗
PubMed2005

The relative effectiveness of various instructional approaches in developing anticipation skill.

The relative effectiveness of explicit instruction, guided discovery, and discovery learning techniques in enhancing anticipation skill in young, intermediate-level tennis players was examined. Performance was assessed pre- and postintervention, during acquisition, and under transfer conditions designed to elicit anxiety through the use of laboratory and on-court measures. The 3 intervention groups improved from pre- to posttest compared with a control group (n = 8), highlighting the benefits of perceptual-cognitive training. Participants in the explicit (n = 8) and guided discovery (n = 10) groups improved their performance during acquisition at a faster rate than did the discovery learning (n = 7) group. However, the explicit group showed a significant decrement in performance when tested under anxiety provoking conditions compared with the guided discovery and discovery learning groups. Although training facilitated anticipation skill, irrespective of the type of instruction used in this experiment, guided discovery methods are recommended for expediency in learning and resilience under pressure.

Adolescent↗
PubMed2005

The relative age effect in youth soccer across Europe.

The potential asymmetries in the birth-date distributions of youth soccer players across ten European countries (2175 age citations) were considered. First, we examined the birth-dates of players representing national youth teams in international competitions. Second, the birth-dates of players representing professional club teams in international youth tournaments were analysed. Kolmogorov-Smirnov tests were used to assess differences between observed and expected birth-date distributions. Regression analyses were employed to examine the relationship between month of birth and number of players in the different samples. The results showed an over-representation of players born in the first quarter of the selection year (from January to March) for all the national youth selections at the under-15 (U-15), U-16, U-17 and U-18 age categories, as well as for the UEFA U-16 tournaments and Meridian Cup. Players with a greater relative age are more likely to be identified as "talented" because of the likely physical advantages they have over their "younger" peers. Some options for reducing the relative age effect are offered.

Adolescent↗
PubMed2005

Practice, instruction and skill acquisition in soccer: challenging tradition.

The acquisition of soccer skills is fundamental to our enjoyment of the game and is essential to the attainment of expertise. Players spend most of their time in practice with the intention of improving technical skills. However, there is a lack of scientific research relating to the effective acquisition of soccer skills, especially when compared with the extensive research base on physiological aspects of performance. Current coaching practice is therefore based on tradition, intuition and emulation rather than empirical evidence. The aim of this review is to question some of the popular beliefs that guide current practice and instruction in soccer. Empirical evidence is presented to dispel many of these beliefs as myths, thereby challenging coaches to self-reflect and critically evaluate contemporary doctrine. The review should inform sports scientists and practitioners as to the important role that those interested in skill acquisition can play in enhancing performance at all levels of the game.

Decision Making↗
PubMed2005

Online attentional-focus manipulations in a soccer-dribbling task: implications for the proceduralization of motor skills.

A focus of attention on the step-by-step control of a skill has been shown to be detrimental to experts' performance but to have no significant effect on novices' performance (e.g., S. L. Beilock, T. H. Carr, C. MacMahon, & J. L. Starkes, 2002), contrary to the results of manipulations of the direction of attentional focus (e.g., G. Wulf, M. Höss, & W. Prinz, 1998). In previous studies, researchers have not separated the focus of attention from the nature of the instruction provided or the skill level of the participants. In the present experiment, 10 skilled and 10 less skilled soccer players dribbled a ball after receiving instructions directing attention to an internal, skill-relevant feature (foot); an internal, skill-irrelevant feature (arm); or a skill-irrelevant task (word-monitoring). Performance was evaluated in relation to a no-attentional-focus control condition. For skilled performers, an internal focus on the arms and feet interfered with performance. For less skilled performers, an internal, yet skill-relevant, focus of attention (foot) did not degrade performance, whereas attention to the arms and word monitoring had a detrimental effect. No significant differences were observed across the three attentional manipulations when the skilled performers used the nondominant foot. The results generally supported the deautomization of skills hypothesis.

Adult↗
PubMed2004

Do pattern recognition skills transfer across sports? A preliminary analysis.

The ability to recognize patterns of play is fundamental to performance in team sports. While typically assumed to be domain-specific, pattern recognition skills may transfer from one sport to another if similarities exist in the perceptual features and their relations and/or the strategies used to encode and retrieve relevant information. A transfer paradigm was employed to compare skilled and less skilled soccer, field hockey and volleyball players' pattern recognition skills. Participants viewed structured and unstructured action sequences from each sport, half of which were randomly represented with clips not previously seen. The task was to identify previously viewed action sequences quickly and accurately. Transfer of pattern recognition skill was dependent on the participant's skill, sport practised, nature of the task and degree of structure. The skilled soccer and hockey players were quicker than the skilled volleyball players at recognizing structured soccer and hockey action sequences. Performance differences were not observed on the structured volleyball trials between the skilled soccer, field hockey and volleyball players. The skilled field hockey and soccer players were able to transfer perceptual information or strategies between their respective sports. The less skilled participants' results were less clear. Implications for domain-specific expertise, transfer and diversity across domains are discussed.

Adaptation, Physiological↗
PubMed2002

Anticipation skill in a real-world task: measurement, training, and transfer in tennis.

Anticipation skill in tennis was examined using realistic film simulations, movement-based response measures, and a portable eye movement recording system. Skilled players were faster than their less skilled counterparts in anticipating the direction of opponents' tennis strokes, with this superior performance being based, at least in part, on more effective visual search behaviors. The processes mediating superior performance were then modeled in groups of recreational tennis players using video simulation, instruction, and feedback. Players who received perceptual training improved their performance on laboratory- and field-based tests of anticipation when compared with matched placebo and control groups that did not receive any instruction regarding expert performance strategies. The approach used may have practical utility in a variety of performance contexts.

Adult↗
PubMed2002

Quiet eye duration, expertise, and task complexity in near and far aiming tasks.

. Skilled (n = 12) and less skilled (n = 12) billiards players participated in 2 experiments in which the relationship between quiet eye duration, expertise, and task complexity was examined in a near and a far aiming task. Quiet eye was defined as the final fixation on the target prior to the initiation of movement. In Experiment 1, skilled performers exhibited longer fixations on the target (quiet eye) during the preparation phase of the action than their less skilled counterparts did. Quiet eye duration increased as a function of shot difficulty and was proportionally longer on successful than on unsuccessful shots for both groups of participants. In Experiment 2, participants executed shots under 3 different time-constrained conditions in which quiet eye periods were experimentally manipulated. Shorter quiet eye periods resulted in poorer performance, irrespective of participant skill level. The authors argue that quiet eye duration represents a critical period for movement programming in the aiming response.

Adult↗
PubMed2002

Head, eye and arm coordination in table tennis.

The aim of this study was to determine the role of head, eye and arm movements during the execution of a table tennis forehand stroke. Three-dimensional kinematic analysis of line-of-gaze, arm and ball was used to describe visual and motor behaviour. Skilled and less skilled participants returned the ball to cued right or left target areas under three levels of temporal constraint: pre-, early- and late-cue conditions. In the pre- and early-cue conditions, both high and low skill participants tracked the ball early in flight and kept gaze stable on a location in advance of the ball before ball-bat contact. Skilled participants demonstrated an earlier onset of ball tracking and recorded higher performance accuracy than less skilled counterparts. The manipulation of cue condition showed the limits of adaptation to maintain accuracy on the target. Participants were able to accommodate the constraints imposed by the early-cue condition by using a shorter quiet eye duration, earlier quiet eye offset and reduced arm velocity at contact. In the late-cue condition, modifications to gaze, head and arm movements were not sufficient to preserve accuracy. The findings highlight the functional coupling between perception and action during time-constrained, goal-directed actions.

Adult↗