AUGMENTED FEEDBACK

Feedback provides both a motivational and informational role. That is, feedback can help to encourage repeated performance and also to reduce the discrep-ancy between a desired and an actual outcome. It is this second, informational role that is of most concern here. Although the motivational role of the coach is undoubtedly important to performance change, it is the type of information that is delivered and how it is delivered that is most important in encouraging specific changes in performance.

3.2.1 Positive effects

It has been proposed that both KR and KP (extrinsic information sources) help to confirm a person’s own judgement about outcome success that is based on intrinsic information sources. Alerting to success of an outcome will lead to continued performance if the result was successfully achieved and a change in performance if it was not (see Figure 3.1). We can distinguish between two different ways of providing feedback about outcome success. This feedback can be qualitative or quantitative. A general statement alerting to the success of the action, such as ‘good’ or ‘bad’ or ‘too much’ or ‘too little’, would be considered qualitative in nature. This information is typically not as precise as quantitative feedback. A more specific statement referring to the amount of error, such as

‘you missed by 25 cm’ would be considered quantitative. The amount of infor-mation conveyed by either source will also be somewhat dependent on the motor skill, and the knowledge of the performer. There have been many experiments where the precision of outcome-based feedback has been exam-ined. Generally, early in practice, qualitative and quantitative KR typically have similar effects on performance. After an initial period of practice (which would depend on the difficulty of the task), more precise quantitative information can be used more effectively to reduce error.

In general, the positive effects of outcome-based feedback, typically KR, have been observed during the practice or what we refer to as the acquisition or performance phase of skill learning. Repeated feedback from trial to trial will lead or guide the learner to the correct response. The learner is provided with enough information to promote change in performance across practice such that

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goal-attainment can be achieved. KR and KP can help to alert the learner to errors such that corrections can be made. It has been shown that so powerful are the effects of outcome feedback that even when this feedback is incorrect and contradicts valid information from intrinsic sources such as vision, learner’s prioritise this extrinsic information and erroneously correct performance (see Buekers et al. 1992). This finding is of course worrying if there are errors with measurement tools or with the coach’s perception (as was discussed in Chapter 1).

As long as the learner knows whether an error has been made, there is a strong likelihood that changes in performance will be observed. Even withholding KR can be informational if the performer realizes that error information is only provided once performance falls outside a certain criteria or bandwidth. For example, if feedback is only provided when an archer misses the target board, then the learner also knows that on the trials when feedback is not provided that she or he was successful. If a change in a response is not encouraged through KR and the skill has not been performed to the degree of required success then the information is probably not specific enough and therefore not sufficient.

3.2.2 Negative effects

It is also important to note that precise, quantitative information about perform-ance and frequent feedback can also impact negatively on performperform-ance during the practice phase causing variable (unstable) performance. Knowledge of an error, whether this is within 1 s, or 1 ms, could lead to an over-correction of performance. If the level of feedback is too specific for the level of control, which the performer is able to exert over the skill, then this feedback could prevent stable performance and hinder outcome success. The level of feedback provided should therefore be appropriate for the skill level of the individual and appropriate to the level of control they have over their performance. Despite this instability, which might result from frequent provision of precise KR, very rarely are negative effects from providing KR observed during the practice phase of learning.

However, true learning can only be effectively assessed at a later time period.

Performance changes during practice might be only temporary and not relatively permanent long-term adjustments (see Schmidt and Lee 2005). To separate these temporary or transient effects from more long-term effects, the acquisition or practice phase has been distinguished from the retention phase (could be equivalent to competition for athletes). In laboratory-based studies, this reten-tion phase is introduced at least 24 h after the last practice session and typically

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without augmented feedback. During the retention phase of testing, conditions should match those that will be encountered by the performer during evalu-ation. For example, a long-jumper who is provided with augmented feedback about error in footfall, in relation to the take-off board during practice, will not typically have this information available under competitive conditions. In con-trast, outcome information concerning the length of the jump remains during the test phase, so the assessment of the skill with this information is a valid and realistic measure of learning. In view of the need to adequately assess what has been learnt by the performer, we need to examine the relationship between performance and learning under different conditions of augmented feedback.

As we will show, the effects of feedback are remarkably dependent on the type of assessment. In fact, these effects are so strong that researchers have shown conflicting performance and retention effects, such that the greater the benefits of feedback seen during the practice phase of skill acquisition, the greater the detriments observed in the test or retention phase (see Salmoni et al. 1984 for more details).

One of the most serious effects of regular performance feedback is that the learners who receive it become dependent on it. This dependence leads to poor performance when the feedback is withdrawn. This has been referred to as the guidance hypothesis of feedback (Salmoni et al. 1984; Winstein and Schmidt 1990). One of the consequences of receiving extrinsic feedback on every per-formance attempt is that the learner does not need to evaluate their own intrinsic feedback, such as evaluating how the movement felt. They do not engage in a form of self generated error detection. When extrinsic feedback is no longer available the learner is unable to judge the accuracy of their movements.

The amount of feedback and when it is delivered could have a significant impact on how dependent the performer will be on this information for accurate per-formance. Very generally, feedback provided at the same time the skill is being performed, referred to as concurrent feedback, has been found to be more guiding and promote greater dependency than feedback about task success provided after the movement has been completed, referred to as terminal feed-back. Vander Linden and colleagues (1993) found that concurrent feedback about the amount of force expended during an elbow extension task was more helpful at reducing error in acquisition when compared with terminal feedback.

However, when performance was assessed in retention, the concurrent feed-back group performed with the most error. Concurrent feedfeed-back guides the performer to the correct response such that they do reduce error based on other sources of intrinsic information. There is no incentive to engage in

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error-detection and actively work out why an error occurred and what changes in the movement led to the correction of this error.

Similar to the negative effects of concurrent feedback, feedback provided imme-diately after the movement has also been shown to discourage the learner from being actively involved in the error detection process and interpreting intrinsic information sources. Although feedback needs to be provided very soon after the actual movement, when it is provided too soon after movement completion, negative effects in retention are likely to result.

Finally, there have been a number of studies on the frequency of providing KR which have demonstrated that a high frequency of instructor-provided aug-mented feedback is detrimental for later performance in retention tests. Again, the mechanisms behind frequent KR appears to be related to a decreased reli-ance on other natural, intrinsic information sources available from performing the action (such as the feel and the visual consequences of the movement) and a failure to spontaneously evaluate how effective the actions were in achieving the desired outcome.

As should be clear from all of these studies, the negative effects of feedback in retention can in most cases be quite simply overcome by reducing the frequency of feedback during practice and increasing the time delay between feedback and successive practice attempts. Even encouraging learners to evaluate their own performance in the interval between the end of the action and KR can help to overcome potentially negative consequences in retention. Such reduction in frequency measures include: (1) an overall reduction in the relative frequency of feedback, for example, providing feedback on 50 per cent of the trials; (2) fading schedules of feedback, whereby the frequency is gradually reduced as a function of practice; (3) bandwidth feedback, which is only provided when error falls markedly outside performance guidelines (which might work in a similar way to a fading schedule as the frequency of feedback is reduced as participants’ learn);

(4) summary feedback, provided after a block of practice trials relating to all the trials in a general manner (such as mean performance), or perhaps only the previous trial; and finally, (5) self-selected feedback, whereby the learner determines when feedback is needed and when it is not.

Knowing the optimal amount of feedback to provide is difficult to prescribe accurately. Very generally, it is the reduction in the relative frequency of KR that is more important than the actual amount of feedback. There is also an import-ant balance to be maintained in that providing feedback too infrequently has been shown to be somewhat equivalent to providing feedback after every trial.

An optimal frequency allows for self-directed (intrinsic) error detection, but does

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not allow performance to depart too markedly from the goal or criterion. A slightly slower rate of acquisition, as a result of a reduction in feedback, will result in enhanced performance in retention relative to a performance when feedback is provided every trial. This reduction in feedback frequency will also prevent the over-correction of errors during practice that can lead to instability in responses.

3.2.3 Additional factors to consider when providing feedback Although we have discussed potential negative consequences associated with providing too much feedback, there are instances when frequent feedback in practice is actually desirable for learning (and hence retention). Generally, it has been shown that more frequent feedback is beneficial for acquiring features of a movement that change across different skills of a similar class of action, referred to as the absolute features of a movement. For example, in shooting a basketball, the overall force of a throw will change across similar shots from different dis-tances outside the key. However, a reduction in feedback benefits the learning of the more stable or relative features of the shot (i.e. the throwing action, which might be indexed by the consistent relative timing of the knee bend, body straightening and release of the ball). There is also evidence that the effects of feedback are dependent on the complexity of the skill. It seems that for tasks that are rich in intrinsic information about how the movement feels, frequent feed-back helps the learner know how to relate the intrinsic feedfeed-back to outcome success. In this way, the learner is able to make more refined judgements about success.

As a result of this research and similar studies, Swinnen (1996) has recom-mended that optimal summary length should become close to every trial as the complexity of the task increases. Although there is no specific criteria that can describe a task as more complex than others, typically more complex tasks require the learning of new relationships between a number of body segments, they are rich in intrinsic feedback and might involve more degrees of freedom (such as whole body movements) in comparison to more simple tasks. Wulf and Shea (2004) have suggested that because of these differences between complex and simple skills feedback provided in more complex skills typically serves less of a guiding role. Knowing that a shot cleared the top goal post by 1 m in soccer does not guide the learner to the correct solution for reducing this error. There are many features of the movement that can be changed to reduce the height of the ball (such as the positioning of the head and trunk when the ball is struck, the

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follow through of the kicking leg, the force imparted on the ball). In contrast, if the movement is constrained to one limb moving in one dimension (i.e. horizon-tally as is typical in many simple target aiming experiments), then feedback about the error in displacement guides the performer in terms of what to change on the next trial (i.e. the extent of the contraction). These dual roles of aug-mented information as a description of what was done and a guide as to what should be done (Figure 3.1) are elaborated on below, when we discuss the role of demonstrations and instructions in the motor learning process.