Learning and executing skills

Athletes have reported the use of both imagery (Munroe et al., 2000; Nordin & Cumming, 2005a; Short et al., 2004; White & Hardy, 1998) and self-talk (Gammage et al., 2001; Hardy

et al., 2001a) to facilitate the learning and execution of skills. When used independently of

self-talk, athletes have been found to employ the use of imagery to learn, memorise, improve, plan (Nordin & Cumming, 2005a), acquire, rehearse, perfect, maintain, automate (White & Hardy, 1998), execute and correct (Munroe et al., 2000) skills.

Cognitive specific (CS) imagery is the most commonly reported imagery type for facilitating the learning and execution of skills (Short et al., 2004), although it has been found that dancers also make use of metaphorical, execution, body-related and context images to serve this function (Nordin & Cumming, 2005a). Examples of such images

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include; imagining falling into sand, and the vertebrae rotating as the spine moves into different positions.

Athlete reports of the use of imagery to facilitate the acquisition and execution of skills are supported by a plethora of experimental research. Much of the early experimental research into imagery compared its effect on the performance of simple motor tasks with physical practice. Findings frequently revealed that although imagery was no replacement for physical practice, it was better than doing nothing at all (Driskell et al., 1994; Feltz & Landers, 1983).

As a consequence of the influential role that imagery has been found to play in the acquisition and execution of skills, a number of theories have been proposed to explain how the strategy works in serving this function (Holmes & Collins, 2001; Jacobson, 1931; Sackett, 1934). The psychoneuromuscular theory (Jacobson, 1931) was one of the first theories proposed, suggesting that imagery facilitated the learning and execution of skills through muscle memory strengthening. More specifically, this theory argued that the vivid imagination of a task could result in activity occurring, although to a lesser extent, in the same muscles that would be activated if the movement or task was to actually physically occur. Jacobson (1931) found initial support for his theory when he assessed ocular and bicep muscle activity under different imagined bicep curl conditions (no imagery, visual imagery and kinaesthetic imagery). Results revealed, with small numbers, that ocular muscle activity was higher during the visually imagined bicep curls, and that muscular bicep activity was higher during the kinaesthetically imagined bicep curls. Jacobson (1931) concluded that imagery was not an activity that occurred solely in the brain and suggested that there might be a neuromuscular mechanism.

Despite these early findings Slade, Landers, and Martin (2002) found less conclusive support for the psychoneuromuscular theory when they assessed electromyographic (EMG) activity in the biceps and triceps during real and imagined arm curling exercises using dumbbells. Results revealed that although there was activation in the muscles in the imagined condition it was not representative of what was observed during the real movements. Smith, Collins, and Holmes (2003) found a similar lack of agreement between imagined and actual muscle activation when they conducted a study comparing the effects of

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physical and mental practice on finger strength and EMG activity. The limited support for the psychoneuromuscular theory has led to suggestions that it is not a viable explanation for how imagery works in facilitating the learning of skills (Feltz & Landers, 1983).

Shortly after the proposal of the psychoneuromuscular theory, the symbolic learning theory (Sackett, 1934) was presented in opposition to explain how imagery worked in facilitating the learning and execution of skills. Instead of suggesting a neuromuscular mechanism, the symbolic learning theory proposed that imagery aided the acquisition of skills through the development of mental blueprints for tasks. Sackett (1934) found initial support for his theory when he found that mental practice successfully aided the retention of a maze task. This was supported by later research that found imagery to be more effective in facilitating cognitive tasks rather than motor tasks (Driskell et al., 1994; Feltz & Landers, 1983). These findings appeared to suggest that imagery enhances cognitive processes rather than neuromuscular ones.

Although the symbolic learning theory has received support, the last decade has seen the development of the functional equivalence theory as a more thorough explanation for how imagery works in facilitating the learning and execution of skills (Holmes & Collins, 2001). The functional equivalence theory (Holmes & Collins, 2001) has drawn upon principles from both the psychoneuromuscular (Jacobson, 1931) and symbolic learning theories (Sackett, 1934), and suggests that imagery facilitates the acquisition and execution of skills through the replication of what happens at a central (brain), peripheral (muscles) and behavioural level when a movement or task is physically undertaken.

The development of the functional equivalence theory led Holmes and Collins (2001) to suggest that athletes‟ imagery use should replicate real life situations as closely as possible in order for the greatest performance effects to be experienced. As a result, they developed a seven item checklist (frequently referred to as PETTLEP) to ensure the creation of vivid images. They argued that the physical properties of the situation (positions, clothing, equipment etc.), environment, task (how you would think and feel), timing, stage of learning, emotions and visual perspective all need to represent real life as closely as possible in order to ensure a facilitation in the learning and execution of skills.

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Over the course of the last ten years there has been a surge in research examining the functional equivalence theory in sport (Smith & Collins, 2004; Smith & Holmes, 2004; Smith, Wright, Allsopp, & Westhead, 2007; Smith, Wright, & Cantwell, 2008; Wright & Smith, 2007). Support for the theory, and the PETTLEP principles, has been resounding with findings from a recent study revealing that PETTLEP informed imagery training led to an increase in bunker shot performance similar to that experienced when physical practice was undertaken (Smith et al., 2008). As a result, the functional equivalence theory is now the most widely accepted theory for explaining how imagery works in facilitating the learning and execution of skills.

Despite the wide support for the functional equivalence theory it has been suggested, particularly with skilled athlete populations, that imagery might work in facilitating the execution of skills by increasing their automaticity (Feltz & Landers, 1983). Field-based research has identified that expert dancers and slalom canoeists widely report the use of the strategy to memorise and automate their skills (Nordin & Cumming, 2005a; White & Hardy, 1998). Despite this, there is limited experimental support for the use of imagery in serving this function, although Thomas and Fogarty (1997) found that instructional and positive imagery and self-talk training led to greater perceptions of automaticity and improved performance in golf. Although this provides some initial evidence for the role of imagery in the elevation of automaticity, its individual contribution in serving this function was unknown as self-talk was also central to the intervention. As such, the functional equivalence theory still remains the most supported explanation for how imagery works in facilitating the learning and execution of skills.

As with imagery, early research into the functions of athlete self-talk focussed mainly on the role that it played in the learning and execution of skills. Results were found to be supportive of the use of the strategy in serving this function, across a range of sports and skill levels (Landin & Herbert, 1999; Ming & Martin, 1996; Ziegler, 1987). Although there is currently limited theoretical support for the way in which self-talk works in serving a variety of functions (Hardy, 2006), it has been proposed that the strategy enhances the learning and execution of skills through both directing (Landin & Herbert, 1999) and shifting (Hardy, 2006; Hardy et al., 2010) attentional focus to the correct cues, aiding the decision making process, and initiating the correct effector mechanisms (Hardy et al., 2010; cf. Landin, 1994 for a review; Landin & Herbert, 1999).

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The clear experimental support for the use of both imagery and self-talk in facilitating the learning and execution of skills has made it appealing to recommend the combined use of the strategies in serving this function (Hardy et al., 2001a). However, before these recommendations can be formulated, a number of factors pertinent to the independent use of imagery and self-talk need to be considered. Firstly, although there is much support for the role of imagery in facilitating the learning and execution of skills, there are still a number of ambiguities as to which imagery content is most appropriate for serving this function. For example, there is incomplete understanding as to which imagery perspective (Callow & Hardy, 2004; Hardy & Callow, 1999; White & Hardy, 1995), attentional foci (Bernier & Fournier, 2010; Caliari, 2008), and nature (Shaw & Goodfellow, 1997; Taylor & Shaw, 2002; Woolfolk, Murphy, Gottesfeld, & Aitken, 1985a; Woolfolk, Parrish, & Murphy, 1985b) is most appropriate for facilitating the learning and execution of skills. Similar attention is warranted with regards to both the optimum nature of self-talk for serving this function, and the problems associated with its use during competition. Consequently, the following section of this review will appraise some of the factors that may influence the effective use of imagery and self-talk in facilitating the learning and execution of skills. It is important to consider these factors as they may have implications for the combined use of the strategies when facilitating the learning and execution of skills.

It is well understood, as a result of the development of the functional equivalence theory (Holmes & Collins, 2001; 2002), that effective imagery is both vivid and multisensory. In addition to this understanding, it is widely accepted that there is considerable individual variation between athletes in their ability to form these „clear‟ images (Isaac, 1992). Despite this, there is still limited knowledge as to which imagery perspective is most effective when imagining the execution of skills. When athletes create images of the execution of skills, they can do so from either an internal or external perspective (Callow & Hardy, 2004; Hardy & Callow, 1999; White & Hardy, 1995). An internal imagery perspective involves imagining doing something as if in one‟s own body. An external perspective involves imagining doing something as though standing outside of the body looking upon one‟s self (White & Hardy, 1995). There are several reasons why there is limited understanding about which imagery perspective is most effective for the execution of skills.

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Firstly, early definitions of imagery perspective were often confused with imagery modality (Hall, 1997; Morris et al., 2005; White & Hardy, 1995). Both Mahoney and Avener (1977) and Mahoney, Gabriel, and Perkins (1987) defined internal imagery as the kinaesthetic imagination of doing an action within the body and external imagery as the visual imagination of doing something outside of one‟s body. As a consequence of these incorrect definitions, early field-based research that examined which imagery type elite athletes reported using most, found that elite athletes reported using internal imagery (confused with kinaesthetic imagery) more than external imagery (Mahoney & Avener, 1977; Mahoney et

al., 1987). As a result, it was suggested that this was the more effective imagery perspective

for optimal performance (Mahoney & Avener, 1977; Mahoney et al., 1987).

However, when more accurate definitions were applied, research revealed that both internal and external imagery perspectives could be used to invoke kinaesthetic imagery, thus potentially adding support to the efficacy of both imagery types (Hardy & Callow, 1999; White & Hardy, 1995). The inducement of kinaesthetic imagery is deemed to be indicative of effective imagery use and optimal performance, as it works in replicating „real life‟ more effectively than imagery that does not employ its use (Holmes & Collins, 2001). Later research by Callow and Hardy (2004) further found that external imagery was more positively related to kinaesthetic imagery use than internal imagery in tasks dependent on form. It was argued that this was because in tasks, where form is important, one must have a clear visual image of where their limbs need to be in order to experience kinaesthetic sensations.

Leading on from this line of enquiry, it was hypothesised that the effectiveness of internal and external imagery may be task dependent (White & Hardy, 1995). More specifically, it was proposed that internal imagery would be more effective for tasks based on perception and modification (e.g. slalom-canoeing) because athletes could practice changes in visual fields using internal imagery. In contrast, it was suggested that external imagery would be more beneficial for tasks dependent on form (e.g. gymnastics), because athletes could use imagery to create a model from which they could learn (White & Hardy, 1995).

There has been mixed support for these proposals. For example, Hardy and Callow (1999) presented findings from three studies that supported the suggestion that external imagery

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was more effective in developing skilled performers‟ execution of tasks dependent on form (karate, gymnastics, bouldering). However, when White and Hardy (1995) examined the effects of internal and external imagery on both a task dependent on perception and modification (indoor slalom canoe), and a task dependent on form (movement sequences for rhythmic gymnastics), results revealed that the use of internal imagery resulted in fewer errors on the slalom canoe task, but that external imagery resulted in quicker performance times. The authors explained this unexpected result from two perspectives. Firstly, they suggested that the competitive nature of the task may have caused the external imagery group to perform more quickly than the internal imagery group. However, the most conceivable explanation for the internal imagery group‟s slower race times was that they were exposed to higher processing loads as a result of having to convert course information from an external perspective to an internal perspective.

No support for the use of external imagery on the form dependent task was found, although it was suggested that the low skill level of participants for this task may have resulted in them showing no improvements. This is likely due to the fact that performance is extremely variable in the early stages of learning (Schmidt & Lee, 2005). Moreover, research has revealed that the benefits associated with the use of imagery on completely novel skills are limited because athletes have no mental blueprints of the skill on which to build (Ramsey, Cumming, & Edwards, 2008). Despite these considerations, before using the findings to reject the task demands hypotheses, a methodological flaw in the study must be discussed. It was apparent that the participants were not provided with any imagery training or guidance. It is common practice to provide athletes with guidelines for the creation of images (Callow & Hardy, 2004; Hardy & Callow, 1999). The lack of guidance could have meant that the participants were unable to create controlled images of the task and, as a consequence, experienced no improvements in performance.

The ambiguity in the literature presented means that there is still limited understanding as to which imagery perspective is most appropriate for facilitating the execution of skills. Moreover, recent research has suggested that other factors may also dictate the effectiveness of internal and external imagery. For example, the development of the functional equivalence theory led Holmes and Collins (2001) to suggest that the use of internal imagery was more effective than external imagery because it replicated „real‟ life more closely. There is support for the use of imagery that has adopted the use of the PETTLEP guidelines over imagery that does not (Smith, Wright, & Cantwell, 2008). However, it is difficult to

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ascertain the individual contribution that the use of internal imagery has over external imagery when considering this research.

In addition, findings from descriptive studies by Fournier, Deremaux, and Bernier (2008) and Bernier and Fournier (2010) appear to suggest that preferences for the use of internal and external imagery perspectives may be dependent on skill level and sport type. For example, Fournier et al. (2008) found that less skilled skydivers used external imagery perspectives more than expert skydivers, who were found to make more use of internal imagery perspectives. Additionally, Bernier and Fournier (2010) found that highly skilled golfers were more reliant on the use of internal imagery perspectives. As a consequence of these initial findings, further research is warranted to determine the performance effects associated with the use of different imagery perspectives when these potential influential determinants of use are considered.

The research profiled demonstrates that there is still limited understanding with regards to which imagery perspective is most appropriate for facilitating the learning and execution of skills. There have been suggestions that the efficacy of the strategies may be task (Hardy & Callow, 1999), skill level (Fournier et al., 2008) and sport-type dependent (Bernier & Fournier, 2010). Furthermore, as previously stated, it has more crudely been suggested that internal imagery may be more effective than external imagery as it replicates „real‟ life more closely (Holmes & Collins, 2001). The mixed messages regarding which imagery perspective is most appropriate, when using the strategy to facilitate the learning and execution of skills, make it difficult to formulate recommendations for how imagery should be used to serve this function. Consequently, at this stage, it may be most appropriate to adopt the recommendations forwarded by Gordon, Weinberg, and Jackson (1994). Upon finding no differences in the effectiveness of internal and external imagery in cricket bowling performance, they proposed that athletes should employ the use of the imagery type that they feel most comfortable employing.

Building upon findings relating to imagery perspective, recent research has looked more specifically at the most appropriate attentional foci to adopt when creating images of the execution of skills (Bernier & Fournier, 2010; Caliari, 2008). It is widely understood that when athletes learn or execute skills they can adopt either an internal or external attentional

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focus. For example, one can focus on the outcome effects of their movements or on the movements themselves (Wulf & Prinz, 2001). When adopting an external focus, it has been further specified that athletes may take a proximal (focussing on an external object close to oneself e.g., focussing on the position of a golf clubface) or distal focus (focussing on an external object far away from oneself e.g. the trajectory of a golf ball; McNevin, Shea, & Wulf, 2003). Current research suggests that athletes‟ performance may benefit from the use of an external distal focus more than an external proximal or internal focus because it better allows for the use of natural control mechanisms (Bell & Hardy, 2009; McNevin et al., 2003). This is deemed to be of benefit because high level performance is characterised by the autonomous execution of skills (Schmidt & Lee, 2005). Furthermore, the active internalisation of focus on the execution of skills has been found to lead to their over conscious analysis and subsequent degradation (Mullen & Hardy, 2000).

The concept of attentional foci has recently been applied to the study of imagery with it being argued that when athletes imagine the performance of skills, they may similarly adopt different internal and external foci (Bernier & Fournier, 2010; Caliari, 2008). Research into the effectiveness of different imaginal attentional foci on the performance of skills has produced mixed results. For example, novice athletes were found to perform a table tennis forehand task better when they imagined the skill from a proximal external attentional focus (imagining the trajectory of the racket) than they did when they imagined it from a distal external attentional focus (imagining the trajectory of the ball; Caliari, 2008). To date, no research has examined the performance effects associated with skilled athletes‟ use of different imaginal attentional foci. However, field-based research has provided some indication of the preferences that skilled athletes have for the adoption of different attentional imaginary foci when using the strategy to facilitate the execution of skills (Bernier & Fournier, 2010). In contrast to the study by Caliari (2008), research into expert golfers‟ use of imagery revealed that they preferred to imagine the outcome of a golf stroke (the trajectory of the golf ball) more than they did the process of performing the stroke (the swing; Bernier & Fournier, 2010). Although there is no performance data to support the use