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

Human Movement Science 24 (2005) 283–307

www.elsevier.com/locate/humov

Perceptual-cognitive expertise in sport: Some considerations when applying the expert

performance approach

A. Mark Williams a,b,¤, K. Anders Ericsson c

a Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, The Henry Cotton Building, 15-21 Webster Street, Liverpool, L3 2ET, UK

b Human Performance Laboratory, Learning Systems Institute, Florida State University, Suite 254, 2010 Levy Avenue, FL 32306-2738, USA

c Department of Psychology, Florida State University, P.O. Box 1270, FL 32306-1270, USA

Available online 10 August 2005

Abstract

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 expertperformance and to consider implications for undertaking research work in the area of percep-tual-cognitive expertise in sport. The expert performance approach presents a descriptive andinductive approach for the systematic study of expert performance. The nature of expert per-formance is initially captured in the laboratory using representative tasks that identify reliablysuperior performance. Process-tracing measures are employed to determine the mechanismsthat mediate expert performance on the task. Finally, the speciWc types of activities that lead tothe acquisition and development of these mediating mechanisms are identiWed. General princi-ples and mechanisms may be discovered and then validated by more traditional experimentaldesigns. The relevance of this approach to the study of perceptual-cognitive expertise in sportis discussed and suggestions for future work highlighted. 2005 Elsevier B.V. All rights reserved.

* Corresponding author. Address: Research Institute for Sport and Exercise Sciences, Liverpool JohnMoores University, The Henry Cotton Building, 15-21 Webster Street, Liverpool, L3 2ET, UK. Tel.: +44151 231 2121; fax: +44 151 231 4353.

E-mail address: [email protected] (A.M. Williams).

0167-9457/$ - see front matter 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.humov.2005.06.002

mailto: [email protected]

mailto: [email protected]

284 A.M. Williams, K.A. Ericsson / Human Movement Science 24 (2005) 283–307

PsycINFO classiWcation: 2330; 2340; 2343

Keywords: Expert performance; Mediating mechanisms; Acquisition; Practice

1. Introduction

Aside from its signiWcant intuitive appeal research on expertise in sport is impor-tant both for theoretical and practical reasons. Theoretically, sport provides a partic-ularly fruitful domain in which to explore the validity of models developed in otherWelds. The majority of sport is performed in a dynamic, ever-changing environment,under conditions of extreme stress where the limits of human behavior and achieve-ment are being continually challenged and extended. Elite athletes strive to overcomeobstacles and constraints in their endeavors to achieve excellence, providing a richsource of empirical evidence on the true potential of human achievement (Ericsson,2003a, 2003b). At a practical level, knowledge of the factors underpinning the devel-opment of expert performers in sport can help highlight the important factors under-pinning eVective practice and instruction and the important social support networksrequired to facilitate performance and learning in other domains. The scientiWc studyof expert performance in sport therefore provides an excellent opportunity for thoseinterested in enhancing performance across domains and has direct implications forother Welds such as human factors, artiWcial intelligence and movement science.

The study of expertise has its historical roots in mainstream psychology and theclassical work of de Groot (1965) who examined the complex thoughts and mecha-nisms that mediated the selection of moves by world-class chess players. de Grootreported that expert performers were able to perceive good chess moves (but notnecessarily the best ones) very rapidly—within seconds—and that these percep-tions were mediated by their extensive knowledge of meaningful game conWgura-tions. He also observed that memory for chess positions increased as function ofexpertise. Simon and Chase (1973) elaborated on de Groot’s work and proposedthe Wrst theory of expertise based on the theoretical framework of human informa-tion processing (Newell & Simon, 1972). They argued that expert chess playersdevelop extensive knowledge of game speciWc patterns as a result of many years ofexperience within the domain. These complex patterns allow experts to retrieveappropriate chess moves from memory. In addition, the same patterns mediateexperts’ superior memory for chess positions by permitting them to group andchunk together individual chess pieces into larger and more meaningful patternswithin the severe capacity constraints of short-term memory (Miller, 1956). In con-trast, less skilled players can only perceive individual pieces or simpler patternswhich limit their recall of chess positions from memory. In support of their theorythey showed that expert chess players were more accurate than their less expertcounterparts in recalling representative situations from chess games when pre-sented for brief periods of time, whereas, in contrast, this superiority disappearedwhen the patterns were broken up by randomly re-arranging the same chess pieces

A.M. Williams, K.A. Ericsson / Human Movement Science 24 (2005) 283–307 285

before presentation (see Chase & Simon, 1973a, 1973b). Allard, Graham, andPaarsalu (1980) reproduced the experts’ superior memory for meaningful ratherthan random stimuli using the sport of basketball. Other researchers have subse-quently shown a relationship between immediate recall of game positions andexpert performance in sports such as soccer, basketball, and American football (fora review, see Starkes, Helsen, & Jack, 2001; Williams, Davids, & Williams, 1999).

Ericsson and Smith (1991) argued that the theory of expertise proposed by Simonand Chase (1973) was overly restrictive, necessitating that the working-memorydemands of processing had to be managed within the Wxed limits of short-term mem-ory capacity (for a more detailed review, see Ericsson, Patel, & Kintsch, 2000). Erics-son and colleagues (e.g., Ericsson, 1996, 1998; Ericsson & Kintsch, 1995; Ericsson &Lehmann, 1996) suggested that experts acquire sophisticated and complex skills thatenable them to either circumvent or simply change the suggested limits on workingmemory. These skills promote both the rapid encoding of information in long-termmemory and enable selective access to this information when required, expanding theavailable capacity in short-term memory. Experts therefore are able to expand theirworking memory capacity so that they can successfully engage in planning, reason-ing, evaluation, and other demanding activities needed for superior performancewithin their domain (see Ericsson & Delaney, 1999).

In response to growing criticism of the original general theory of expertise,Ericsson and Smith (1991) proposed a descriptive and inductive framework for thestudy of expertise which they refereed to as the expert performance approach. Threeimportant stages in the empirical analysis of expert performance were identiWed. TheWrst stage necessitates that performance be observed in situ in an attempt to capturethe essence of expertise in the domain of interest and to design representative tasksthat allow component skills to be faithfully reproduced in the laboratory. In thesecond stage the aim is to determine the mediating mechanisms that account forexpert performance using process-tracing measures such as verbal protocol analysis,eye movement recording, and/or representative task manipulations. Knowledge ofthe underlying processes can help facilitate theoretical development and improveunderstanding of the factors that contribute to expert performance. The Wnal stageinvolves eVorts to detail the adaptive learning and explicit acquisition processes rele-vant to the development of expertise, with potential implications for practice andinstruction. The expert performance approach and some of the methods and mea-sures that may be employed at each stage is illustrated in Fig. 1.

The framework proposed by Ericsson and Smith (1991) provided a timely impetusand helped guide the empirical study of expertise over the ensuing decade, althoughfew researchers may be deemed to have fully embraced its philosophical underpin-nings (Ericsson & Lehmann, 1996; Ericsson, 2003a). In recent publications there hasbeen stimulating debate as to the relative strengths and weaknesses of the expert per-formance approach as well as its associated conceptual pillars such as long-termworking memory theory and the notion of deliberate practice (see Abernethy,Farrow, & Berry, 2003; Ericsson, 2003a, 2003b). The aim in this paper is not to reiter-ate arguments presented elsewhere (e.g., see Starkes & Ericsson, 2003), although someoverlap of material may be needed to maintain coherency in relation to the key


arguments, rather the intention is to focus the discussion more speciWcally on percep-tual-cognitive expertise in sport. The aim is to review the expert performanceapproach and to consider potential implications for those interested in capturing andenhancing perceptual-cognitive skills such as anticipation and decision making. Thisstrategy is not designed to undermine the importance of research work on motorexpertise more broadly or to imply any likely theoretical distinction between percep-tual-cognitive and perceptual-motor processes, merely an attempt to limit the scopeof the current article. We begin by considering what it actually entails to captureexpert performance.

2. Capturing perceptual-cognitive expertise in sport

The challenge facing scientists in the Wrst stage of the expert performanceapproach is to identify the essence of perceptual-cognitive expertise within thedomain in question and to eVectively capture the component skills in the laboratory(or Weld setting) using a representative task(s). The task(s) employed should provideprecise and reproducible measurements so that the development of performance canbe objectively evaluated. The performance of experts on these tasks should not altersigniWcantly over repeated tests since the intention is to monitor stable processes thathave been modiWed and adapted over extended periods of practice. The above chal-lenges may be relatively straightforward in tasks where there is a clear and measur-able performance outcome such as, for example, with running or swimming eventswhere the time taken to complete the course provides an accurate measure ofachievement. However, behavioral constructs such as anticipation and decision mak-ing are diYcult to assess in the Weld setting and to isolate for systematic investigationand evaluation under controlled conditions in the laboratory. So, how should scien-tists begin to design tasks to characterize perceptual-cognitive expertise in sport?

Fig. 1. An illustration the expert performance approach and some of the methods and measures that maybe used at each stage.

Capture ExpertPerformance

IdentifyUnderlyingMechanisms

Examine HowExpertise

Developed

Laboratory-testingVideo and FilmVirtual Reality

Field-testingMatch AnalysisSimulations

Process-tracing MeasuresEye MovementsFilm OcclusionBiomechanical ProfilingEvent Related PotentialsVerbal Reports

Practice History ProfilingQuestionnairesInterviewsLog BooksTime-Motion AnalysisVerbal Reports

Learning StudiesTraining Interventions


Although most scientists would aspire to carry out well-designed and controlledexperiments with good ecological or external validity, the issue of contention is theextent to which individuals are willing to loosen their grip on the former to achievegains in the latter. The tendency, particularly within the closely related Weld of motorbehavior, has been to design simplistic and often novel tasks in order to test a prevail-ing theoretical framework. Typical examples of such tasks within the motor domaininclude linear movement devices, the pursuit rotor and stabilometer, whereas in thestudy of perceptual-cognitive expertise the use of simple and choice reaction timemeasures provide similar examples (for a review, see Williams et al., 1999). Whilstthese types of tasks may help identify basic mechanisms, they are unlikely to revealthe speciWc and often complex mechanisms that control and mediate truly expert per-formance. Novel tasks require unique solutions, often those for which the expert isno better prepared than the novice. As indicated by Abernethy, Thomas, andThomas (1993), simplistic or contrived laboratory tasks are likely to remove theexperiential eVects for the expert’s advantage, introducing potential Xoor or ceilingeVects on performance, and causing experts to use diVerent information to that whichthey would normally use to solve a particular problem. It is likely that more realisticsimulations enhance measurement sensitivity, increasing the possibility of identifyingmeaningful and important diVerences between skilled and less skilled performers.

The design of representative perceptual-cognitive tasks within the domain of sportis challenging, particularly given the dynamic and rapidly changing nature of thedisplay, the need for precise motor actions, and the inherent physiological andemotional demands on performance. However, scientists now have access to sophisti-cated and sensitive tools that should help uncover the mysteries of truly expert per-formance. For example, high quality visual images may be easily created in thelaboratory using digital video technology coupled with large screen presentation for-mats (e.g., see Williams, Ward, Knowles, & Smeeton, 2002). Participants may beasked to verbally indicate quickly and accurately the opponent’s intentions or tomove in response to the action sequences. In the latter scenario, pressure-sensitivepads located at strategic positions on the Xoor may be linked to a computer-basedtimer to record the time and accuracy of response. Alternative methods for assessingparticipant response include the use of infra-red motion detectors, optoelectronicmotion analysis systems, force plates, in-shoe pressure sensors, electrogoniometersand high-speed video. These devices provide accurate and sensitive measures of per-formance while at the same time providing participants with freedom of movement.

An important advantage of Wlm and video is that it enables sequences of action tobe reproduced in a consistent manner from trial to trial, providing an objectivemethod of evaluating performance. Many sports contain sequences of events that arerarely if ever repeated in an exact form (Ericsson, 2003b). Moreover, in team sports,individuals have diVerent roles to fulWll (e.g., oVensive vs. defensive role) increasingthe diYculties involved when attempting to capture the essence of expert perfor-mance. The same action sequence may be Wlmed or recorded on video from theunique perspective of each individual enabling the mechanisms mediating superiorperformance in each positional role to be eVectively identiWed (e.g., see Ward,Williams, Ward, & Smeeton, 2004).


Virtual reality displays may also be created by using optoelectronic motion analy-sis systems to create ‘virtual’, three-dimensional models of opponents and using‘CAVE’ like presentation formats such that athletes become more immersed in theirperformance environment (see http://www.e-motek.com). Data gloves and other suchdevices may further heighten the Wdelity of the simulation. Unfortunately, few withinthe domains of sport and movement science have embraced the potential beneWts ofusing virtual reality technology to simulate the performance setting in this manner(for exceptions, see Dessing, Peper, & Beek, 2004; Walls, Bertrand, Gale, & Saunders,1998). The disadvantages associated with increased Wnancial cost and reduced imagequality when compared with video have generally outweighed the potential beneWtsthat may be associated with three dimensional viewing environments and the abilityto interact with objects and others in a virtual recreation of the performance setting(see Ward, Williams, & Hancock, in press).

While expensive virtual reality simulations are more routinely used in military set-tings, cost-conscious sport psychologists have typically invested greater eVort inattempting to capture performance in the Weld setting. For example, high-speed video,liquid crystal occlusion glasses, digital video technology, satellite and micro-chip playerand ball tracking technology may all be used to an extent to help evaluate aspects ofsporting performance in situ (see Carling, Williams, & Reilly, in press; Rodrigues,Vickers, & Williams, 2002; Starkes, Edwards, Dissanayake, & Dunn, 1995). Similarly,simulations of match situations may be realistically acted out on the Weld of play so asto enhance reproducibility and experimental control (e.g., see Starkes & Lindley, 1994).However, systematic evaluation may be confounded by the diYculty involved whenattempting to recreate the standardized and reproducible conditions needed for com-parisons between and within groups. The confound may be alleviated to a degree byevaluating performance over time in a number of related scenarios so as to reduce theeVects of this potential variability and identify reliable aspects of behavior.

Numerous questions remain to be answered adequately when attempting todesign representative task simulations to capture perceptual-cognitive expertise insport. These questions include: Does video adequately capture the dynamics of sport-ing action or should testing in the Weld be encouraged? Do virtual reality environ-ments oVer advantages over and beyond video capture of performance footage?When video is employed, should the image size be body-scaled using large screen dis-plays or can performance be adequately captured using standard size monitors?Should the links between perception and action be maintained in the laboratory set-ting or can representative tasks be designed to capture eVectively perceptual-cogni-tive skill without the need to physically interact with the environment? Doesperformance on these task simulations vary as function of the amount of contextualinformation provided prior to performance (i.e., speciWc knowledge relating to theopponent or score/stage within the match)? Should researchers attempt to mimicother performance demands during testing such as physiological fatigue, competitiveanxiety, and threat of injury? These are important questions and, bar a few notableexceptions (e.g., see Abernethy, 1990; Williams & Elliott, 1999; Williams, Ward,Allen, & Smeeton, 2005), there have been few empirical attempts to provide prescrip-tive guidance for those interested in eVectively capturing perceptual-cognitive

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expertise in sport (for a more detailed review, see Williams & Ward, 2003; Williamset al., 1999).

It should also be acknowledged that it may be diYcult in certain instances to cap-ture the essence of perceptual-cognitive expertise within the sport and consequently,researchers sometimes design laboratory tasks that measure a related function orability. For example, rather than having experts elicit a representative response to apresented situation, such as making a chess move or hitting a ball, researchers haveoften instructed participants to recall aspects of that situation or to make familiarity-based judgments on viewing representative stimuli (for a review, see Ericsson &Lehmann, 1996; Williams et al., 1999). Although experts repeatedly perform betterthan novices on such tasks, the relationship between these memory skills for mean-ingful stimuli and actual performance may not be as strong as initially expected(Ericsson et al., 2000; Ericsson & Smith, 1991). For example, Williams and Davids(1995) showed that although recall performance was the strongest predictor of antici-pation skill in soccer the overall proportion of the variance across skill groupsaccounted for by this variable was not high. Similar observations have been notedwithin many other domains of expertise, such as chess (see Ericsson et al., 2000).

Scientists should therefore be cautious when inferring that the perceptual-cogni-tive processes which mediate performance on tasks that measure a related ability areessential for superior performance in actual competition. A possible solution may beto develop a battery of perceptual-cognitive tasks so that their relative contributionto expert performance may be evaluated (e.g., see Helsen & Starkes, 1999; Ward &Williams, 2003; Williams & Davids, 1995). The task which accounts for the largestproportion of the variance in performance across skill groups could then be used toundertake a more detailed evaluation of the mechanisms mediating expert perfor-mance (e.g., see Ward, Williams, & Ericsson, 2003). Those experts who demonstratetruly exceptional performance on the most representative task may then be used togarner more detailed knowledge using single-participant, case study designs, anddetailed process-tracing measures.

Several other issues are relevant when designing experiments that adequately cap-ture expert performance. These issues which include the appropriate deWnition ofparticipant groups, the need to diVerentiate between experience and skill in partici-pant selection, and greater emphasis on using longitudinal and single-participantdesigns rather than the ubiquitous cross-sectional, between-group design arediscussed in detail elsewhere and not reiterated here (see Abernethy et al., 1993;Williams et al., 1999). Next, we consider how researchers can identify the underlyingmechanisms that contribute to expert performance on the task.

3. Identifying the perceptual-cognitive mechanisms that mediate expert performance

After developing a task or collection of tasks to eVectively capture perceptual-cog-nitive expertise in the sport, the aim is to apply a range of methods to identify themediating mechanisms underlying the expert’s superior performance over the novice.Generally, this is an aspect of the expert performance approach that scientists have


often overlooked. The overriding tendency in the domain of sport expertise has beento merely identify diVerences in performance between skilled and less skilledperformers rather than to explicate and analyze the mediating mechanisms thatcontribute to expertise. A detailed description of the structure of the underlyingperceptual-cognitive processes is essential to the development of complete concep-tual models of expert performance, enabling researchers to move away from meredescription to explanation and prediction of expert performance. Fig. 2 illustrates thediVerent measures that may be collected before, during or after performance on atask to identify the underlying perceptual-cognitive processes. A brief outline of someof these techniques follows.

3.1. Eye movement recording

Video-based corneal reXection systems have been employed to measure the per-ceiver’s point-of-gaze in sport contexts. These systems work by linking togetherinformation from the corneal reXex and pupil, obtained via an infra-red light sourceand a camera focused on the eye, with an image of the scene of interest, provided byeither a head- or Xoor-mounted camera. Although diVerent types of eye movementsmay be measured (e.g., saccades, pursuit-tracking), researchers within the sport

Fig. 2. A schematic illustrating the diVerent types of process-tracing measures and task manipulationsthat may be employed to identify mediating mechanisms (adapted from Ericsson and Smith, 1991).

Start of Task —Presentation of Stimulus

End of Task —Generation of Response

Response Time/Accuracy

Outcome Measures

Post-task Observations

• Retrospective Reports

• Post-experimentInterview

Fixation Fixation Fixation

Visual Search Behavior

V1 V1 V1V1

Concurrent Verbalizations

Process Measures

Pre-task Manipulations

• Film Occlusion

• Point-light Displays

• Distortion of Image

ProcessingStep 1

ProcessingStep 1

ProcessingStep n


sciences have mainly focused on the Wxations that separate these eye movements;somewhat of a misnomer given that this approach is generally referred to as eyemovement recording. The location of each Wxation indicates an area of interest,whereas the number and duration of Wxations provides an index of the amount ofinformation processed by the performer. These indices are thought to reXect theunderlying search strategy used to extract meaningful information from the display.The above assumptions are not universally accepted however and several potentiallimitations should be acknowledged. The most problematic of these are the poten-tial distinction between “looking” and “seeing” (i.e., Wxating an area withoutextracting information) and “Wxation” and “information extraction” (i.e., Wxatingan area while extracting information from elsewhere using the parafovea or visualperiphery). These limitations necessitate that researchers consider employing com-plimentary observations of information extraction such as verbal protocol analysisor experimental interventions, such as occlusion of presented information (for amore detailed discussion of these issues, see Williams et al., 1999; Williams, Janelle,& Davids, 2004).

Although such systems have been around for some time, only recently has tech-nology improved to the point where their use within dynamic, sport contexts maybe considered routine. Initially, data collection procedures typically required par-ticipants to remain stationary, often using a chin-rest and bite bar to restrict headmovements, while watching static images of sporting scenarios (for a review, seeWilliams et al., 1999). However, more recent systems are far easier to use than theirpredecessors enabling data to be collected using dynamic, movement basedresponse protocols both in laboratory and Weld settings (see Williams, 2002;Williams, Ward, & Smeeton, 2004). Calibration and data collection procedures arenow simpler and less time consuming, whilst much lighter head-mounted optics andtelemetry-based data recording devices have signiWcantly improved the portabilityof these systems. Other reWnements such as the development of high-speed camerasystems which enable data to be sampled at 240 frames-per-second and daylightshooting units for use outdoors during sunlit hours have further increased systemcapability (see http://www.a-s-l.com). Rodrigues and colleagues (2002) have pro-vided an example of how improvements in technology have impacted positively onthe ability of scientists to collect data in meaningful, real-world contexts.

A signiWcant constraint in using this approach is the amount of time taken toanalyze the data. Generally, video taped data are analyzed post-hoc using frame-by-frame video analysis. Several software packages have emerged in recent years thathelp reduce data analysis time. These packages enable almost automated data anal-ysis when a static visual image or computer screen is employed to project the stimuliof interest. Areas or zones of interest are identiWed in the visual scene prior torunning the analysis. When dynamic Wlm stimuli are employed, the researcher has toidentify areas of interest on every single frame of Wlm, increasing considerably theamount of time needed to be invested prior to running the analysis. Pattern tracingsoftware is currently being developed in an attempt to alleviate this problem (e.g.,see http://www.eyeresponse.com). Frame-by-frame video analysis currently remainsa necessity where data is collected in the Weld setting.

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3.2. Film occlusion and point-light displays

Film occlusion techniques have been around for some time. The temporal occlu-sion approach involves Wlming the appropriate display (e.g., penalty kick in soccer)from the player’s (e.g., goalkeeper) customary perspective. The Wlm is then selectivelyedited at diVerent points to provide the participant with a varying amount ofadvance (e.g., information available prior to an event such as foot/ball contact) andball Xight information. The Wlm is then presented using a repeated trials design withparticipants being required to predict the end result of each sequence observed. Anindication of the key time-windows for information extraction across skill groups isprovided, with experts typically relying on earlier sources of information to predictshot outcome (for a review, see Abernethy, 1987; Williams et al., 1999).

In order to determine both the time and nature of the information extracted, a spatialor event occlusion technique must be used along with temporal manipulations of the dis-play. In the spatial occlusion approach, participants are presented with Wlm sequenceswhere speciWc cue sources (e.g., non-kicking foot, arm, and trunk) are occluded, typically,but not necessarily, for the entire duration of the trial. The presumption is that if there is adecrement in performance on the trial when a particular cue is occluded, compared with anon-occluded control condition, the importance of the occluded source of information ishighlighted. The time of occlusion of each cue can be manipulated to provide a clearerindication of what sources of information are important at each stage in the action.

The initial attempts to use this approach were handicapped by existing technologywith opaque markers having to be meticulously placed onto each frame of action,when presented using 16 mm Wlm (e.g., see Abernethy, 1988, 1990; Abernethy &Russell, 1987). This fairly course technology was subsequently replaced by video-based analogue editing systems which enabled black boxes to be superimposed overthe Wlmed images (see Williams & Davids, 1998). The disadvantage with these tech-niques was that it was often possible to pick out the outline of the obstructed cue byfocusing on the movement of the opaque mat or box over time. More recently, theadvent of digital video technology and advanced software packages (see http://www.pinnacle.com) has enabled the foreground (e.g., the player’s hips) to be replacedwith the background (e.g., the playing surface/turf). Parts of the visual scene are liter-ally erased from each frame of action. Williams, Hodges, North, and Barton (inpress) have provided an illustration of how this technology can be used to removeplayers from structured sequences of play in soccer.

Another approach has been to use point-light displays to recreate aspects of the visualscene. Point-light images were initially employed by Marey (1895/1972) and then appliedto the study of human movement by Johansson (1973). These displays are generally con-structed by attaching reXective tape or markers to the major joint centres of the body,recording the body in motion, then displaying the reXective markers alone against a blackbackground. The intention is to remove background and contextual information and topresent movement in its simplest terms (Cutting & ProYtt, 1982). Several researchershave proposed that the eVective pick up of relative motion (captured by sequences ofpoint-light displays) is an essential component of anticipation skill in fast-ball sports (e.g.,see Abernethy, Gill, Parks, & Packer, 2001; Ward, Williams, & Bennett, 2002). The

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argument is that performers determine an opponent’s intentions based on their percep-tion of the relative motion between speciWc bodily features, rather than via the extractionof information from more superWcial features or an isolated area or cue. A relatedhypothesis currently being examined in our laboratories is that relative motion providesinformation related to the direction of an opponent’s shot, whereas the velocity of theend-eVector (e.g., arm, foot) is essential for predicting the ‘weight’ or depth of the shot.Another recent extension has been to use this technique to identify the importance ofrelational information between players (i.e., positions and motions of players) when per-ceiving patterns of play in a dynamic team sport (see Williams et al., in press).

The method of presenting images in point-light form can be combined with tempo-ral and spatial occlusion techniques. Images may be temporally occluded at predeter-mined time points and/or individual or collective markers removed for all or part of atrial. Modern methods of creating point-light images using optoelectronic motion cap-ture systems rather than video provide signiWcant advantages in this regard since it isrelatively easy to remove the coordinates for certain markers from the entire sequenceas opposed to having to edit out this part of the image on every frame of video. Anadditional advantage provided by using motion analysis systems is that it is possible todistort parts of the image by modifying the data coordinates in the associated softwareWle. The distortion of a key perceptual feature may provide participants with a verydiVerent challenge to that presented when an aspect of the visual scene is removed.

A disadvantage with Wlm and point-light based occlusion techniques is that the meth-ods employed are very time consuming, requiring many hours of fairly tedious editingwork. Moreover, some initial judgements have to be made to determine which sources ofinformation to occlude and when, introducing the possibility of experimenter bias. Arepeated measures design is also used with the same action sequence being presented onseveral occasions, depending on the number of occlusion conditions employed, increasingthe possibility of order or learning eVects. Although alternative between-group designsmay be employed, there are diYculties involved in attempting to match participants andtrial diYculty across conditions. Perhaps the biggest limitation is presented by the factthat experts may base their decisions on several concurrent and overlapping perceptualcues. If there is no decrement in performance when a particular cue is occluded (e.g., pen-alty taker’s hips in soccer), this need not imply that performers do not normally extractinformation from this area of the display when available, merely that the same informa-tion was extracted from some other source(s) on this occasion. This perceptual Xexibilityor redundancy is likely to be an important characteristic of expert performance in sport.

3.3. Biomechanical proWling and data reduction techniques

The proWling of various movement skills has been a routine endeavor in both clin-ical and applied biomechanics for many years, with a particular focus on identifyingabnormalities in human gait patterns and the important technical components ofsports skills. Thus far, and perhaps rather surprisingly, these techniques have notbeen used to identify how experts perceive kinematic information relating to antici-pation skill in sport. An optoelectronic motion analysis system may be used to helpprovide an in-depth proWle of various sports skills such as the tennis forehand shot or


penalty kick in soccer. The biomechanical diVerences between cross-court and down-the-line tennis shots or penalty kicks struck to the right or left side of the goal canprovide a principled basis for identifying subtle diVerences in the perceptual cues thatmay be visible to performers (see Smeeton, Huys, Williams, & Hodges, 2005). Forexample, biomechanical proWling of the soccer penalty kick may indicate muchgreater rotation around the hip region when the ball is placed to one side of the goalor the other, implying that this area of the body provides useful predictive informa-tion when attempting to anticipate ball destination.

Biomechanical data may be analyzed at varying levels. The simplest level of analy-sis would be to examine the data using angle-angle plots or by extracting simplequantitative measures such as joint range of motion, angular displacement, andangular and liner velocity proWles. Cross-correlations can be used to examine aspectsof intra-limb coordination (see Horn, Williams, & Scott, 2002). A more sophisticatedapproach would be to use data reduction techniques such as multiple regression orprincipal component analysis to identify diVerences. Principal component analysismay be used to reduce high-dimensional data sets into a smaller number of structuresor components (see DaVertshofer, Lamoth, Meijer, & Beek, 2004). The technique cantease apart the structural components (or invariance) of the task and, more impor-tantly in lieu of the current discussion, help identify those factors that discriminatebetween two sets of related data (e.g., down-the-line vs. cross-court forehand driveshots in tennis). The conclusions drawn using these techniques may be veriWed usingWlm occlusion or point-light display techniques to either remove or distort compo-nents identiWed in the analysis. Post, DaVertshofer, and Beek (2000) and Huys,DaVertshofer, and Beek (2004) have highlighted some examples of how the principalcomponent analysis approach can identify the components of skill in three-ball cas-cade juggling. Work is ongoing in our laboratories to examine whether this approachcan also help identify structure within team games such as soccer.

An added advantage when collecting biomechanical data is that these may be usedto create three-dimensional simulations of the skill in question. These simulationsenable the skill to be viewed from any angle or perspective, whereas aspects of thedisplay such as a particular limb may be highlighted, removed or distorted. Suchmanipulations are potentially useful both for testing and training purposes. Thesesimulations may be presented on conventional computer and video screens or usingimmersive, virtual reality technology.

A potential disadvantage with this approach that should be acknowledged is thatit is necessary to impose some functional limitations on performance by, for example,having consistent start and end positions for the movement. Whilst such an approachprovides an element of control and reproducibility, and simpliWes quiet markedly theensuing data analysis process, generalizability of Wndings to dynamic, real-life scenar-ios may be compromised.

3.4. Psychophysiological measures of selective attention

Psychophysiological measures of attention are now used extensively in sport.There is published literature involving the use of positron emission tomography,


functional magnetic resonance imaging, electroencephalography (EEG), event-related potentials (ERP), galvanic skin response, heart rate variability, pupil dilation,and blood pressure recording amongst other such measures (for a review, see Janelle,Duley, & Coombes, 2004). Most of these measures provide an indication of the levelof activation of the system (i.e., arousal) rather than the allocation of attention per se,although such information is helpful in identifying the mechanisms by which expertsovercome emotional constraints on performance.

The ERP may be used to provide an index of selective attention in sport (e.g., seeJanelle et al., 2004). The measure is derived from EEG data and represents brainactivity which is time-locked to some event that is thought to reXect discrete psycho-logical processes. Participants typically view stimuli from their customary perspectivewithin the game (e.g., waiting to return serve in tennis) and the ERP waveform istaken at a key moment, such as ball-racket contact by the server. One of the mostwidely studied components of the ERP is the P300 (or P3), which is a positive devia-tion in the ERP waveform that occurs around 300 ms after a key event. The latencyand amplitude of the P3 relative to the onset of the discrete event provides a measureof the attention devoted to the task (particularly stimulus discrimination) at thismoment. Generally, longer latencies imply increased time to classify the stimuli,whereas larger amplitudes indicate that greater attention has been devoted to thestimulus. Radlo, Janelle, Barba, and Frehlich (2001) provided an illustration of howthis procedure may be used to discriminate skilled from less skilled batters in base-ball. The recording of ERPs can be combined with eye movement recording and/orspatial occlusion techniques in an attempt to isolate crucial moments of informationextraction, yet this innovative approach remains to be pursued by ambitiousresearchers in dynamic sport settings.

The inherent movement requirements of most sports introduces artefacts into theacquired ERP signals (and other psychophysiological measures), rendering data col-lection impractical or at best necessitating that the participant remain stationarythroughout data collection. The diYculty is that since these measures can only beemployed under very restrictive laboratory conditions there is an inherent danger inhaving to modify the task environment to such an extent that the task employed nolonger adequately captures the essence of expert performance; a signiWcant potentialconcern in lieu of the philosophical underpinnings of the expert performanceapproach. Moreover, data collection is time consuming and the concerns previouslyarticulated for Wlm occlusion techniques relating to the need for repeated measuresdesigns involving multiple presentations of the same or related stimuli are furtherexaggerated with this approach. Regardless, the collection of ERP data may providea unique window into the chronometry of the brain that is not aVorded by othermeasurements (Janelle et al., 2004).

3.5. Verbal protocol analysis

There has been considerable debate as to the validity of verbal reports on thinking(e.g., see Ericsson & Simon, 1993; Nisbett & Wilson, 1977). The disagreementshave been shown to be the result of diVerences in verbal-reporting procedures.


Participants’ reports are far more accurate when they are asked to give verbalexpression to their thoughts while they perform on a given task as compared to theexplanations of their reasons for why they responded in a certain way.

Ericsson and Simon (1993) described the conditions under which participants areable to accurately report on their mediating thought processes either concurrentlyduring task performance, using think-aloud protocols, or retrospectively immediatelyafter completing the task. The key factor is to ensure that individuals are properlyinstructed to give verbal expression to their thoughts rather than to explain theirsolution for the task to the experimenter or to provide a summary of the generalstrategy adopted. For example, rather than being instructed to verbally report thenumber of players considered when attempting to anticipate an opponent’s inten-tions in soccer participants should be instructed to report the thought process thatcomes to mind as they react to a presented representative situation. Participants nor-mally require only 15 min of instruction and warm-up to give such reports, but insome dynamic situations longer periods of experience with non-domain speciWc tasksare necessary to become suYciently familiar with this procedure prior to data collec-tion. Additional eVort is required to undertake a detailed task analysis of each situa-tion prior to data collection and to transcribe, collate, and analyze verbal protocols.Ward and colleagues (2003) have provided an example of how this type of approachmay be used to explore perceptual-cognitive expertise in soccer. Similarly, Abernethy,Neal, and Koning (1994) have illustrated how this approach may be used to identifythe cognitive processes that mediate shot selection in snooker.

A signiWcant advantage with verbal report protocols is that they provide a win-dow into the cognitive processes that mediate perception and decision-making. Gen-erally, the majority of techniques such as eye movement recording and Wlm occlusiononly indicate the sources of information that athletes use to guide performance. Noattempt is made to determine how experts translate the information obtained fromthese perceptual cues into appropriate tactical decisions. McPherson and colleagues(e.g., McPherson, 1999; McPherson & Kernodle, 2003) have provided some examplesof how these protocols can make a unique and meaningful contribution to the litera-ture on perceptual-cognitive expertise.

In summary, a variety of process measures are available to help researchers iden-tify the mechanisms underlying expert performance in sport. Although each of thesetechniques has speciWc limitations, all potentially contribute to increasing under-standing of perceptual-cognitive expertise in sport. A key issue is that these tech-niques should be viewed as complimentary in nature and a combination of two ormore approaches may be needed to adequately identify the important processes thatmediate exceptional performance on the task. An interesting issue is how researchersshould proceed where there is discrepancy in relation to the main conclusions emerg-ing via independent process-tracing measures. One obvious strategy would be toundertake additional empirical work either using another process-tracing measure orby examining changes in performance following a relevant manipulation of the task.Alternatively, support in favor of one process-tracing methodology over anothermay be derived from existing literature and clearly derived theoretical arguments.More often than not, however, it is likely that two diVerent process-tracing measures


will complement rather than contradict each other, each measure providing addi-tional clariWcation regarding the mechanisms responsible for expert performance onthe task.

Regardless of the particular process-tracing measures employed, an understandingof the processes that mediate expert performer is an important precursor to thedevelopment of theoretical models of expertise that facilitate explanation and predic-tion. The information gathered through process-tracing methods may initiallybe used in an inductive manner to formulate detailed descriptive frameworks or weaktheories of expert performance. These frameworks may eventually be expanded andreWned to present stronger theories that support more deductive, hypothesis-drivenapproaches to conceptual development. The long-term working memory theory pro-posed by Ericsson and colleagues (e.g., see Ericsson, 1998; Ericsson & Kintsch, 1995;Ericsson & Lehmann, 1996) provides an example of how information on expertperformance may be translated into a more deductive theoretical framework for sub-sequent empirical evaluation.

4. Adaptive learning and explicit acquisition processes

The aim in the Wnal stage of the expert performance approach is to determine howexperts acquire the skills needed to demonstrate reliably superior performance. Thisstage was not as well deWned as the Wrst two stages of the approach in its original for-mulation by Ericsson and Smith (1991). However, Ericsson, Krampe, and Tesch-Römer (1993) elaborated on the nature of the acquisition processes underpinningexpert performance by introducing their deliberate practice framework; its theoreti-cal propositions have remained an issue of contention over the ensuing decade. Ericssonand colleagues (1993) proposed that exceptional levels of performance are only rarelylimited by factors associated with innate talent, rather the important mediatingmechanisms are acquired through sustained investment in deliberate practice activi-ties over an extended period of time (in excess of 10 years, the so called ‘10 year rule’,see Simon & Chase, 1973). Engagement in increased deliberate practice is assumed toincrementally improve the mediating mechanisms that result in expert performance.

An important point to highlight is that Ericsson and colleagues (1993) did notsuggest that innate characteristics have no role to play in fostering high level perfor-mance. They acknowledged, for example, that height and body size are clearly relatedto success in many types of sport. Furthermore, Ericsson and colleagues (1993)explicitly suggested that heritable individual diVerences may inXuence important pro-cesses related to motivation, enjoyment of practice, and the capacity to sustainengagement in deliberate practice activities. The gist of their thesis was that there iscurrently no empirical evidence to demonstrate that innate, immutable talents are themain limiting factors preventing individuals from attaining the highest levels of per-formance (Ericsson, 2003b, 2003c). This is a qualitatively diVerent statement to thatinterpreted by many within the Weld (e.g., see Abernethy et al., 2003; Singer & Janelle,1999). The crucial point is that innate talent is unlikely to be the most important fac-tor on the road to excellence; far more important is the intense commitment to


engage in deliberate practice activities with the speciWc intention of further improvingperformance. Whether it be sport, music or academia, an almost obsessive desire tocontinually improve and reWne skills (i.e., a ‘rage to master’, Winner, 1996) is the mostcrucial ingredient in the recipe for success. This claim about the primacy of practice isbased on two main sources of evidence. First, research highlighting the ‘plasticity’ oramenability of cognitive skills to the eVects of practice, and second, a detailed investi-gation of the practice history proWles of experts in various domains. The research evi-dence from each of these two strands of evidence is brieXy considered, with particularemphasis on work relating to perceptual-cognitive expertise, and Wnally, potentialimplications for practice and instruction are highlighted.

4.1. Plasticity of perceptual-cognitive skills

Skilled performers are able to extend or overcome the limits imposed by basic infor-mation processing capacities such as visual reaction time and short-term memory(Ericsson et al., 2000). This ability is particularly evident in the sporting arena wherethere are numerous examples of how experts overcome such structural constraints bydeveloping speciWc perceptual-cognitive mechanisms as a result of practice. For exam-ple, in fast ball sports such as tennis experts overcome signiWcant temporal constraintsby developing knowledge structures that enable them to anticipate expected actionrequirements. The ability to eVectively pick up advance postural cues, to scan the visualdisplay in an appropriate manner, and to orientate attention only to the most pertinentsources of information are due to speciWc adaptations as a result of practice and expe-rience on the task (Williams, Ward, & Chapman, 2002). In team games such as soccer,the ability to detect patterns of play and to use situational probabilities to prime thesearch for relevant contextual information are further illustrations of the plasticity andadaptability of the underlying perceptual-cognitive processes (Williams, 2000).

These adaptations do not occur simply through changes in chronological age orbiological maturity. For example, Abernethy (1988) showed that the ability to antici-pate an opponent’s intentions based on postural cues improves with experiencerather than age by comparing the performance of 12, 15, and 18 year old elite bad-minton players with age-matched control groups of novice players. Ward andWilliams (2003) reported similar conclusions with soccer players between 8 and 17years of age using a battery of soccer-speciWc tests of perceptual-cognitive expertise.The older age groups generally showed better performance when compared withtheir younger counterparts and age-matched control groups involving sub-elite play-ers. These results demonstrate that expertise results in speciWc adaptations as a resultof practice and experience rather than simply a by-product of maturation. AlthoughWard and Williams (2003) reported skill-based diVerences on some of the perceptual-cognitive measures of performance as early as 8–9 years of age, follow-up analysis ofthese players’ practice history proWles indicated that even at this age the elite playershad accumulated an additional 200 h or so of team and individual practice and matchplay compared to age-matched sub-elite players. It is most likely that these additionalhours of accumulated practice contributed signiWcantly to the skill-based diVerencesobserved within this youngest age group.


4.2. Practice history proWles of elite performers

A potentially valuable method to help identify the important adaptive learningand explicit acquisition processes leading to expertise is to examine the practice his-tory proWles of elite performers using questionnaires, interviews, and training logs.The speciWc activities that most eYciently lead to the development of these mediatingmechanisms are described so that general principles may be extrapolated that allowpredictions to be made regarding the eVects of engaging in these activities (Ericsson,2003a, 2003b). The initial attempt was undertaken with musicians (violinists andpianists). Ericsson and colleagues (1993) showed that the best groups of violinistsreported spending an average of over 24 h per week in solo practice, compared witharound 9 h for less expert performers. Retrospective estimates of accumulated prac-tice hours indicated that after 10 years of practice the best violinists had accruedalmost 7500 h of practice, whereas the good and intermediate level performers hadaccumulated just over 5000 and 3000 h respectively. The expert pianists displayedsimilar practice proWles averaging nearly 27 h per week in individual practice, 6000 hmore than their amateur counterparts over their respective career paths.

The relationship between practice and level of attainment was subsequently exam-ined in individual sports such as wrestling (Hodges & Starkes, 1996), Wgure skating(Starkes, Deakin, Allard, Hodges, & Hayes, 1996), and karate (Hodge & Deakin,1996). The elite athletes spent considerable more time in practice than their less elitecounterparts, averaging between 24 and 28 h per week; a Wgure comparable with thetime that expert musicians practice alone in their studio each week (Deakin & Cob-ley, 2003; Ericsson et al., 1993). Ward, Hodges, Williams, and Starkes (2004) reportedthat in soccer the amount of time in team practice was the strongest discriminator ofexpertise, with the elite players spending twice the amount of time per week in teampractice compared with their sub-elite counterparts. As a novel addition to the litera-ture, Ward et al. (2004) required participants to rate those factors which they consid-ered most important in attaining excellence within the sport. The elite soccer playersconsidered that the motivation to succeed allied with the commitment to practice asbeing more important in achieving success than skill level or talent.

4.3. Implications for research in the area of perceptual-cognitive expertise

Although evidence supporting the importance of practice in fostering adaptivelearning mechanisms is compelling, a number of questions remain for those inter-ested in enhancing perceptual-cognitive expertise in sport. In particular, can theacquisition of perceptual-cognitive skills be facilitated through appropriate traininginterventions and how are the practice histories of those who are deemed to demon-strate exceptional perceptual-cognitive skills diVerentiated from those who are lessskilled in this regard?

The former question has typically been addressed by recreating the performanceenvironment using video or Wlm (e.g., return of serve in tennis) and then providinginstruction as to the important cues underlying performance, coupled with practiceand feedback (e.g., see Williams et al., 2002; Williams et al., 2002). Although the


literature base is not extensive, and several methodological shortcomings may beidentiWed, results are encouraging and suggest that perceptual-cognitive skills canbe enhanced through relevant interventions using diVerent types of instruction(Williams & Grant, 1999). These experimentally-based manipulations can provideuseful information in the quest to elicit the adaptive learning mechanisms thataccount for expert performance on such tasks. Numerous research opportunitiesexist for those interested in enhancing perceptual-cognitive expertise using suchapproaches, and these are discussed in detail elsewhere (e.g., see Williams & Ward,2003; Williams et al., 2004).

An important development is that those interested in enhancing perceptual-cogni-tive skills have attempted to re-create the real-world performance setting duringpractice using realistic simulations coupled with meaningful instruction. Morerecently, researchers have included sensitive performance measures, Weld-based trans-fer tests, longer intervention periods, and delayed retention tests performed underanxiety-inducing conditions (e.g., see Smeeton, Williams, Hodges, & Ward, in press).These improvements in research design and methodology may be perceived posi-tively in light of the typical inclination in traditional perceptual-motor learning stud-ies to rely on simple, contrived, and often novel experimental tasks to examine issuesrelated to skill acquisition. The tendency has been to remove or control the experien-tial eVect on learning using novel tasks and then to explore the eVects of diVerenttypes of practice and instruction over relatively short periods of time under sterilelaboratory conditions, often without a delayed retention and/or transfer test. Animportant question to ponder is whether the Wndings from these traditional learningstudies have had a meaningful impact on instructional practice in applied domains?

The question of whether the practice history proWles of those who demonstrateexceptional perceptual-cognitive skill may be discriminated from their less advancedcounterparts may be examined using the deliberate practice framework. However,there have been few attempts to examine the speciWc practice activities that facilitatethe acquisition of perceptual-cognitive skills. How do players with excellent percep-tual-cognitive skills diVer in relation to their practice history proWles from those withpoor anticipation and decision makings skills? An answer to this question is essentialif the deliberate practice framework is to provide more meaningful guidance forthose interested in developing perceptual-cognitive skills.

Ward and colleagues (2004) addressed this latter issue by asking soccer players tohighlight the amount of time spent practicing diVerent types of activities during atypical training session. Elite players were observed to spend a much higher propor-tion of their time engaged in activities that necessitated good decision-making skillscompared with less-elite players, although the speciWc nature of these activities werenot elucidated. Similarly, Baker, Côté, and Abernethy (2003a) attempted to identifywhether there were diVerences in the practice history proWles of those who weredeemed to be good and not so good at decision-making in various sports. Someevidence was presented to indicate that those who were deemed to be good decision-makers had participated in a broader range of sports prior to specialising in theirspeciWc sport, although this suggestion was not supported by Ward et al. (2004).Unfortunately, Baker and colleagues (2003a) made no attempt to try and determine


whether diVerences in decision-making skill across groups were directly related tospeciWc practice activities or strategies. This type of guidance is essential for thoseinterested in developing interventions to facilitate the acquisition of such skills(Williams & Ward, 2003).

In a follow-up study, Baker, Côté, and Abernethy (2003b) did attempt to furtherelucidate the types of practices activities in which those individuals perceived to begood decision makers invested more time compared to a control group of sub-elite,yet highly experienced, performers from other sports. However, the categories ofactivities employed were not particularly illuminating and comparisons are weak-ened by the absence of any direct measure of perceptual-cognitive expertise in eithergroup of participants. No attempt was made to classify the control participants basedon their perceptual-cognitive expertise, whereas ratings of the elite players as gooddecision-makers were based purely on the subjective opinion of coaches. It iscertainly not inconceivable, given the variability typically evident with empiricalmeasures of perceptual-cognitive skill, that some of the control participants couldhave been good decision-makers in their own right. Although perceptual-cognitiveskill is an important component of expert performance, it would be incorrect toassume that all experts are good perceivers and decision-makers. A fundamentalcharacteristic of sport is that deWciencies on certain components of performance (e.g.,anticipation) may be addressed by strengths on others (e.g., speed and agility; seeWilliams & Reilly, 2000).

A more worthwhile comparison would be to examine whether a group of elite ath-letes who record high scores on various empirical measures of perceptual-cognitiveskill could be diVerentiated from another group of elite athletes with poorer scores onsuch measures based on accumulated practice hours or on the nature of the practiceactivities undertaken. The quality of practice activities and the nature of the instruc-tion process are likely to be at least as important as the accumulated practice hours indetermining the rate of progress towards excellence. It is therefore important forresearchers to examine the microstructure of practice in order to provide guidance tocoaches as to the types of practice activities and instruction most likely to facilitatethe acquisition of perceptual-cognitive expertise. Time-motion analysis of speciWcpractice sessions and retrospective recall of the underlying performance strategiesemployed during these sessions may help examine this issue. An important questionto answer is ‘what strategies do those players classiWed as good perceivers or decision-makers use during training and matches’? It is possible that diVerences between play-ers with good perceptual-cognitive skills and those who are less enamored with suchskills are a by-product of the speciWc strategies employed during practice rather thanmere exposure to the training stimuli per se. Athletes with exceptional perceptual-cog-nitive skills may well approach the task in a fundamentally diVerent manner to thosewho are less exceptional in relation to these skills. Skilled individuals may display amuch greater awareness of the underlying strategic and tactical aspects of perfor-mance, with these diVerences being apparent in the manner in which they process orrecall information before, during, and after training and match-play.

In order to eVectively address the issues highlighted above, researchers need tocollect process-tracing measures during performance and learning. Some of these


process-tracing measures were considered earlier in this paper. Although the use ofprocess-tracing measures such as movement kinematics is becoming more wide-spread in the motor learning literature, few researchers interested in perceptual-cog-nitive expertise have outlined how the mechanisms mediating performance changewith practice. To examine this issue, researchers would need to record process-tracingmeasures such as eye movements and verbal reports during acquisition, either in thelaboratory- or Weld-setting, in order to better understand the adaptive learning andexplicit acquisition processes that lead to expert performance. Such approacheswould provide a wealth of information that may help explain the eVectiveness ofdiVerent types of practice activities.

An important concern is the extent to which information derived from practicehistory proWles may provide a good basis for providing prescriptive guidance tocoaches. Current coaching practice is determined mainly by anecdotal evidence andhistorical precedence, what has been referred to as the processes of intuition, tradi-tion, and emulation (e.g., see Abraham & Collins, 1998; Lyle, 1999), rather than onempirical research. One should therefore be cautious when providing recommenda-tions for coaches based on the retrospective practice histories of elite athletes forfear of perpetuating existing shortcomings in the instructional process (Williams &Hodges, 2005). To address this issue, it may be necessary to combine research thathas examined the practice history proWles of those classiWed as having exceptionalperceptual-cognitive skills with traditional learning studies performed in the labora-tory. Both approaches are necessary to provide a complete picture of the adaptivelearning processes that result in perceptual-cognitive expertise. The deliberate prac-tice framework may be used to identify those activities and/or strategies likely to beimportant in attaining expertise, whereas validity may be conWrmed in the labora-tory using the more traditional experimental designs recently employed in the per-ceptual-training literature (e.g., see Williams et al., 2002; Williams & Ward, 2003).Some of the advantages and disadvantages of these two approaches are highlightedin Table 1.

In conclusion, the aims in this paper were to review the expert performanceapproach in order to highlight some important considerations for those interestedin perceptual-cognitive expertise. The Wrst stage within the approach necessitatesthat scientists adequately capture and reproduce expert performance to enable itsstudy under controlled experimental conditions. The need to embrace new technol-ogy was highlighted as an important step forward for those interested in this area,enabling scientists to eVectively simulate performance environments and to collectaccurate and reliable measurements. The mechanisms underlying perceptual-cogni-tive expertise must also be discovered and described empirically before meaningfultheoretical accounts can be developed to explain superior performance. A varietyof process-tracing measures were presented and the need for complimentaryapproaches highlighted. The third stage of the expert performance approach neces-sitates that the causal mechanisms which mediate the acquisition of expertise beidentiWed. The speciWc practice activities which lead to adaptive changes in exper-tise can be identiWed by comparing the practice history proWles of elite performerswith high and low levels of perceptual-cognitive skill. Such an analysis may be


extended to examine the underlying processing strategies used during practice andmatch-play. Experimental investigation and manipulation of the learning mecha-nisms is permissible, although scientists are encouraged to focus on using realisticsimulations of the performance environment, long-term training interventions, andto identify changes in the underlying mechanisms as a result of practice. There havebeen signiWcant advances in the study of perceptual-cognitive expertise in recentyears and continued debate regarding the nature of exceptional performance andits acquisition should further stimulate what is already a vibrant Weld of scientiWcendeavour.

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Table 1Some of the advantages and disadvantages when attempting to identify adaptive learning mechanismsusing practice history proWles and traditional learning studies

Retrospective Practice History ProWles Traditional Learning Studies

• Provides a description of the generalstructure of practice activities leadingto expert performance

• Overemphasis on macro rather thanmicro structure of practice

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• Absence of control groups• Potential concerns with validity of

retrospective estimates of practice hours

• Enables the validity of speciWc practiceactivities and instructional procedures tobe examined under controlled laboratory settings

• Overemphasis on using simple and novellaboratory tasks leading to concerns ingeneralizing Wndings to real-worldlearning activities

• Short-term training interventions, mainlywith novice rather than expert participants

• Limited attempts to record process-tracingmeasures of learning

• Often absence of transfer and/or retentiontests, particularly involving realistic stressorssuch as anxiety and fatigue


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