Motor Skill Acquisition and Retention as a Function of Average Feedback, Summary Feedback, and Performance Variability

Reduction of Feedback Availability Limits Self-Control Effects

A growing body of research has demonstrated that providing learners with self-control over aspects of the learning environment facilitates the learning of a motor skill. In applied group settings, however, the provision of feedback is at times constrained by factors such as instructor availability. The purpose of the present study, therefore, was to examine how learners ostensibly provided self-control over feedback responded when the actual availability of feedback was constrained by a predetermined schedule of a virtual coach's availability to provide feedback. Participants were divided into four feedback groups and completed 72 practice trials of a sequential key-pressing task, with three different goal movement times (900, 1,200, 1,500 ms). The KR100 group received knowledge of results (KR) after every practice trial. The KR50 group received KR on an evenly distributed quasi-randomly determined schedule after 50% of the trials. The SC group had the opportunity to request KR after every trial, but KR was only available for 50% of practice trials according to the same schedule used for the KR50 group. The YK (i.e., yoked) group received KR according to the schedule of KR received by counterparts in the SC group. Approximately 24 h after acquisition, each participant returned to complete retention and transfer tests. The retention test consisted of 15 no-KR trials of the acquisition tasks (five trials for each goal time−900, 1,200, 1,500 ms). The transfer test consisted of 15 no-KR trials with new time goals (1,300, 1,600, 1,900 ms). Results revealed a significantly lower absolute constant error (ACE) score for the SC group during transfer (p < 0.05), suggesting that SC effects can occur in a reduced feedback availability environment. Other measures, however, failed to show significant advantages for the SC group during any phase of the study suggesting that effects were not as robust as previous research has indicated. The results also provided some indication that perceived scarcity might have played a role in elevating the number of feedback requests in response to the reduced autonomy environment.

Optimizing Feedback Frequency in Motor Learning: Self-Controlled and Moderate Frequency KR Enhance Skill Acquisition

The purpose of this study was to compare the relative effects of self-controlled knowledge of results (SCKR) to other KR schedules of varying relative frequency (25%, 50%, and 100% of acquisition trials) on motor skill learning. Participants received basic instructions on the soccer overhead throw and then performed 50 acquisition trials, during which KR was provided according to the assigned schedule, followed by a retention test, during which no KR was provided. Retention scores were highest for the SCKR and 50% KR frequency groups who shared comparable absolute KR frequency and distribution relative to successful versus unsuccessful trials. These results indicated that both self-control and moderate frequency feedback enhanced learning, supporting an inverted U-shaped effect of feedback frequency on skill acquisition.

The Effect of Augmented Feedback Type and Frequency on Velocity-Based Training-Induced Adaptation and Retention

Nagata, A, Doma, K, Yamashita, D, Hasegawa, H, and Mori, S. The effect of augmented feedback type and frequency on velocity-based training-induced adaptation and retention. J Strength Cond Res 34(11): 3110-3117, 2020-The purpose of this study was to compare the benefits of 4 weeks of velocity-based training (VBT) using different augmented feedback (AugFb) types and the frequency of AugFb, and whether adaptations are retained 10 days post-training. Thirty-seven collegiate male rugby players were divided into groups that received immediate feedback (ImFb; n = 9), visual feedback (ViFb; n = 10), average feedback (AvgFb; n = 10) and no feedback (NoFb; n = 8) during each VBT session consisting of 3 sets of 5 repetitions of loaded jump squats. The ImFb group received AugFb regarding lifting velocity under loaded jump squats (LV-JS) after every jump, whereas LV-JS measures were averaged after each set of jumps and presented to the AvgFb group. The LV-JS were video-recorded and displayed as kinematic feedback for the ViFb group after each set, although NoFb was provided for the NoFb group. Loaded jump squats measures were reported at baseline, during each training session and 10 days post-training. Loaded jump squats measures were significantly greater for the ImFb Group compared with the other groups during a number of post-baseline time points (p ≤ 0.05). Furthermore, at 4 weeks of VBT and 10 days post-retention, effect size (ES) calculations showed that LV-JS measures were greater with moderate to large effects for the ImFb group compared with the NoFb (ES = 1.02-1.25), AvgFb (ES = 0.78-0.82) and ViFb (ES = 0.74-1.60), respectively. However, LV-JS measures were reduced with moderate to large effects 10 days post-retention for the ViFb (ES = -0.60) and NoFb (ES = -0.85) groups. Providing LV-JS feedback after each jump appears to optimize performance and should be considered as a training tool during VBT.

Sub-optimality in motor planning is not improved by explicit observation of motor uncertainty

To make optimal decisions under risk, one must correctly weight potential rewards and penalties by the probabilities of receiving them. In motor decision tasks, the uncertainty in outcome is a consequence of motor uncertainty. When participants perform suboptimally as they often do in such tasks, it could be because they have insufficient information about their motor uncertainty: with more information, their performance could converge to optimal as they learn their own motor uncertainty. Alternatively, their suboptimal performance may reflect an inability to make use of the information they have or even to perform the correct computations. To discriminate between these two possibilities, we performed an experiment spanning two days. On the first day, all participants performed a reaching task with trial-by-trial feedback of motor error. At the end of the day, their aim points were still typically suboptimal. On the second day participants were divided into two groups one of which repeated the task of the first day and the other of which repeated the task but were intermittently given additional information summarizing their motor errors. Participants receiving additional information did not perform significantly better than those who did not.

Scheduling Concurrent Visual Feedback in Learning a Continuous Balance Task

This investigation held concurrent visual feedback frequency at 50% in the acquisition phase and manipulated three different feedback schedules while comparing those to a 0% feedback frequency. In an assessment of dynamic postural stability, young, healthy adults performed 20 acquisition trials and four retention trials 48-hr later on a circular platform that moved in the anterior/posterior and medial/lateral axes simultaneously. Three concurrent feedback schedules were manipulated: a fade schedule consisting of high relative frequency of concurrent feedback early in the acquisition phase which was systematically reduced throughout acquisition (e.g., 100%, 75%, 50%, 25%, 0%), a constant schedule consisting of a uniform scheduling of concurrent feedback on every other acquisition trial, and a reverse fade group consisting of a schedule exactly opposite to that of the fade group. A no concurrent feedback group was also utilized to determine if feedback was necessary to learn the balance task. Acquisition and retention results revealed the concurrent groups performed with significantly greater accuracy and stability than the no concurrent feedback group. There were no significant differences between the three concurrent feedback schedules. Results indicate that manipulating concurrent feedback scheduling did not produce similar results to those investigations manipulating knowledge of results scheduling.

Investigation of Feedback Schedules on Speech Motor Learning in Older Adults

BACKGROUND

The principles of motor learning (PML) emerged from studies of limb motor skills in healthy, young adults. The applicability of these principles to speech motor learning, and to older adults, is uncertain.

AIMS

The purpose of this study was to examine one PML, feedback frequency, and its effect on retention and generalization of a novel speech and comparable tracing task.

METHODS

Sixty older adults completed a speech motor learning task requiring the production of a novel phrase at speaking rates 2 times and 3 times slower than habitual rate. Participants also completed a limb motor learning task requiring the tracing of a sine wave 2x and 3x slower than habitual rate. Participants were randomly assigned to receive feedback every trial, every 5th trial, or every 10th trial. Mean absolute error was measured to examine immediate generalization, delayed generalization, and 2-day retention.

FINDINGS

Results suggested that feedback frequency did not have an effect on the retention and generalization of the speech or manual task, supporting the small but growing literature highlighting the constraints of generalizing the PML to other modalities and populations.

Ambulatory Voice Biofeedback: Relative Frequency and Summary Feedback Effects on Performance and Retention of Reduced Vocal Intensity in the Daily Lives of Participants With Normal Voices

Purpose

Ambulatory voice biofeedback has the potential to significantly improve voice therapy effectiveness by targeting carryover of desired behaviors outside the therapy session (i.e., retention). This study applies motor learning concepts (reduced frequency and delayed, summary feedback) that demonstrate increased retention to ambulatory voice monitoring for training nurses to talk softer during work hours.

Method

Forty-eight nurses with normal voices wore the Voice Health Monitor (Mehta, Zañartu, Feng, Cheyne, & Hillman, 2012) for 6 days: 3 baseline days, 1 biofeedback day, 1 short-term retention day, and 1 long-term retention day. Participants were block-randomized into 3 different biofeedback groups: 100%, 25%, and Summary. Performance was measured in terms of compliance time below a participant-specific vocal intensity threshold.

Results

All participants exhibited a significant increase in compliance time (Cohen's d = 4.5) during biofeedback days compared with baseline days. The Summary feedback group exhibited statistically smaller performance reduction during both short-term (d = 1.14) and long-term (d = 1.04) retention days compared with the 100% feedback group.

Conclusions

These findings suggest that modifications in feedback frequency and timing affect retention of a modified vocal behavior in daily life. Future work calls for studying the potential beneficial impact of ambulatory voice biofeedback in participants with behaviorally based voice disorders.

Integration of Motor Learning Principles Into Real-Time Ambulatory Voice Biofeedback and Example Implementation Via a Clinical Case Study With Vocal Fold Nodules

PURPOSE

Ambulatory voice biofeedback (AVB) has the potential to significantly improve voice therapy effectiveness by targeting one of the most challenging aspects of rehabilitation: carryover of desired behaviors outside of the therapy session. Although initial evidence indicates that AVB can alter vocal behavior in daily life, retention of the new behavior after biofeedback has not been demonstrated. Motor learning studies repeatedly have shown retention-related benefits when reducing feedback frequency or providing summary statistics. Therefore, novel AVB settings that are based on these concepts are developed and implemented.

METHOD

The underlying theoretical framework and resultant implementation of innovative AVB settings on a smartphone-based voice monitor are described. A clinical case study demonstrates the functionality of the new relative frequency feedback capabilities.

RESULTS

With new technical capabilities, 2 aspects of feedback are directly modifiable for AVB: relative frequency and summary feedback. Although reduced-frequency AVB was associated with improved carryover of a therapeutic vocal behavior (i.e., reduced vocal intensity) in a patient post-excision of vocal fold nodules, causation cannot be assumed.

CONCLUSIONS

Timing and frequency of AVB schedules can be manipulated to empirically assess generalization of motor learning principles to vocal behavior modification and test the clinical effectiveness of AVB with various feedback schedules.

Average KR Schedule in Learning of Timing: Influence of Length for Summary Knowledge of Results and Task Complexity

This experiment investigated the influence of length for average Knowledge of Results (KR) and task complexity on learning of timing in a barrier knock-down task. Participants (30 men and 30 women) attempted to press a goal button in 1200 msec. after pressing a start button. The participant was assigned into one of six groups by two tasks (simple and complex) and three feedback groups (100% KR, Average 3, Average 5). The simple and complex tasks required a participant to knock down one or three barriers before pressing a goal button. After a pretest without KR, participants practiced 60 trials of physical practice with one of the three following groups as a practice phase: one given the result of movement time after every trial (100% KR), a second given the average movement time after every third trial (Average 3), a third given the average movement time after every fifth trial (Average 5). Participants then performed a posttest with no-KR and two retention tests, taken 10 min. and 24 hr. after the posttest without KR. Analysis gave several findings. (1) On the complex task, the absolute constant error (|CE|) and the variable error (VE) were less than those on the simple task. (2) The |CE| and the VE of the 100% KR and the Average 3 groups were less than those of the Average 5 group in the practice phase, and the VE of the 100% KR and the Average 3 group were less than those of the Average 5 group on the retention tests. (3) In the practice phase, the |CE| and the VE on Blocks 1 and 2 were higher than on Blocks 5 and 6. (4) On the retention tests, the |CE| of the posttest was less than retention tests 1 and 2. And, the VE of the 100% KR and the Average 3 groups were less than that of the Average 5 group. These results suggest that the average feedback length of three trials and the given feedback information after every trial are advantageous to learning timing on this barrier knock-down task.

Average-Kr Schedule Benefits Generalized Motor Program Learning

The main purpose of this study was to examine the effects of average Knowledge of Results (KR) on generalized motor program learning and parameter learning. Two groups of participants ( n = 15 per group) performed 80 acquisition trials of sequential timing tasks. All participants were asked to depress sequentially four keys (2, 4, 8, and 6) on the numeric pad portion of the computer keyboard with the index finger of the right hand. The author presented average feedback on timing errors based on 5-trial blocks and compared this feedback schedule with every-trial feedback. Analysis of the delayed no-feedback retention test indicated a strong advantage for the average KR compared with the every-trial condition in both generalized motor program learning and parameter learning. The current results suggest that the average KR schedule may have positive effects on generalized motor program learning and parameter learning.

Frequent feedback enhances complex motor skill learning

Feedback frequency effects on the learning of a complex motor skill, the production of slalom-type movements on a ski-simulator, were examined. In Experiment 1, a movement feature that characterizes expert performance was identified. Participants (N = 8) practiced the task for 6 days. Significant changes across practice were found for movement amplitude and relative force onset. Relative force onset is considered a measure of movement efficiency; relatively late force onsets characterize expert performance. In Experiment 2, different groups of participants (N = 27) were given concurrent feedback about force onset on either 100% or 50% of the practice trials; a control group was given no feedback. The following hypothesis was tested: Contrary to previous findings concerning relatively simple tasks, for the learning of a complex task such as the one used here, a high relative feedback frequency (100%) is more beneficial for learning than a reduced feedback frequency (50%). Participants practiced the task on 2 consecutive days and performed a retention test without feedback on Day 3. The 100% feedback group demonstrated later relative force onsets than the control group in retention; the 50% feedback group showed intermediate performance. The results provide support for the notion that high feedback frequencies are beneficial for the learning of complex motor skills, at least until a certain level of expertise is achieved. That finding suggests that there may be an interaction between task difficulty and feedback frequency similar to the interaction found in the summary-KR literature.

The effect of feedback and practice on the acquisition of novel speech behaviors

PURPOSE

This study examined the effect of manipulating several parameters of motor learning theory on participants' phonetic acquisition and retention of utterances in a foreign language (Korean).

METHOD

Thirty-two native English-speaking participants naïve to the Korean language were each given 10 Korean sentences to practice and learn. The independent variables in the study were the number of practice trials and the feedback schedule. The participants listened to sentences delivered by a native speaker and received feedback according to the schedule. Participant responses were then judged by a panel of native Korean speakers in terms of their intelligibility, naturalness, and precision.

RESULTS

The combination of 20% feedback and 100 practice trials was more effective than other combinations of feedback and practice trial schedule for the retention of novel phonetic productions of Korean phrases both 1 day after training and 1 week later.

CONCLUSIONS

These findings are in agreement with previously reported applications of motor learning-guided principles on the acquisition of motoric skills. These findings may have direct implications for both second-language learning and the treatment of neuromotor speech disorders such as apraxia of speech.

The effect of feedback schedule manipulation on speech priming patterns and reaction time

Speech priming tasks are frequently used to delineate stages in the speech process such as lexical retrieval and motor programming. These tasks, often measured in reaction time (RT), require fast and accurate responses, reflecting maximized participant performance, to result in robust priming effects. Encouraging speed and accuracy in responding can take many forms, including verbal instructions and feedback, and often involves visually displayed RT feedback. However, it is uncertain how manipulation of the schedule of this RT feedback influences speech RT speed and, ultimately, the priming effect. This experiment examined the effect of visually presented RT feedback schedules on priming patterns in 20 older healthy adults. Results suggested that feedback schedule manipulation had a differential effect on reaction time, depending on the interstimulus interval between the prime and the target, but no effect on response priming patterns.

Extrinsic feedback for motor learning after stroke: what is the evidence?

PURPOSE

There is little guidance on using extrinsic feedback to enhance motor learning after stroke. This narrative review synthesises research findings and identifies questions remaining to be answered.

METHOD

A summary is given relating to the use of extrinsic feedback in healthy subjects. Then, research concerning content of feedback, feedback scheduling, and attentional focus is discussed in relation to patients with stroke.

RESULTS

Though research is scarce, preliminary key findings were as follows: Patients' balance performance can improve from receiving visual feedback about weight distribution during practice; auditory feedback of force production may improve performance of sit-to-stand; providing feedback on less than 100% of trials, and giving summary or average feedback may enhance learning; instructions or feedback inducing an external focus may be more effective than those with an internal focus. Further research is needed concerning the relative benefits of verbal, visual, video and kinematic feedback; reduced feedback frequencies and summary feedback schedules; feedback delays, error estimation, and self-controlled feedback; and attentional focus of feedback.

CONCLUSIONS

Although there are some indications that feedback might enhance motor learning after stroke, there are many areas as yet not examined and there is clearly a need for considerable research in this area.

The effects of augmented kinematic feedback on motor skill learning in rifle shooting

In this study, we examined the effects of augmented kinematic knowledge of performance (KP) on shooting performance and learning. Knowledge of performance described the aiming trajectory of the rifle barrel. The effects of knowledge of performance were evaluated in terms of shooting accuracy (shooting score), variability of the shooting score (root mean square error) and rifle stability (x- and y-deviation of rifle movement). The participants (n = 40) were randomly assigned to one of four groups: no-KP, 50% KP, 100% KP and a control group. The three experimental groups performed 480 shots during a 4 week acquisition phase in which feedback was provided. No-feedback retention tests were administered at 2 and 10 days after acquisition. There were no differences between groups during acquisition. In the 2 day retention test, the mean shooting score of the group receiving 100% knowledge of performance was significantly higher than that of the other groups. Furthermore, variability in shooting score for the 100% KP group was lower than that for the 50% KP and control groups. No significant differences were found in rifle stability between the experimental groups. In summary, a high frequency of kinematic knowledge of performance improved shooting accuracy, but the effect appeared to be temporal, disappearing in the 10 day retention test. Given that a parallel effect was not found in rifle stability, future research should focus on examining the reasons for this improvement in shooting score.

Principles derived from the study of simple skills do not generalize to complex skill learning

We review research related to the learning of complex motor skills with respect to principles developed on the basis of simple skill learning. Although some factors seem to have opposite effects on the learning of simple and of complex skills, other factors appear to be relevant mainly for the learning of more complex skills. We interpret these apparently contradictory findings as suggesting that situations with low processing demands benefit from practice conditions that increase the load and challenge the performer, whereas practice conditions that result in extremely high load should benefit from conditions that reduce the load to more manageable levels. The findings reviewed here call into question the generalizability of results from studies using simple laboratory tasks to the learning of complex motor skills. They also demonstrate the need to use more complex skills in motor-learning research in order to gain further insights into the learning process.

Analysis of fMRI and finger tracking training in subjects with chronic stroke

Hand movement recovery and cortical reorganization were studied in 10 subjects with chronic stroke using functional MRI (fMRI) before and after training with an intensive finger movement tracking programme. Subjects were assigned randomly to a treatment or control group. The treatment group received 18-20 sessions of finger tracking training using target waveforms under variable conditions. The control group crossed over to receive the same treatment after the control period. For comparison with a healthy population, nine well elderly females were also studied; however, the well elderly controls did not cross over after the control period. The dependent variables consisted of a Box and Block score to measure prehensile ability (subjects with stroke only), a tracking accuracy score and quantification of active cortical areas using fMRI. For the tracking tests, the subjects tracked a sine wave target on a computer screen with extension and flexion movements of the paretic index finger. Functional brain images were collected from the frontal and parietal lobes of the subject with a 4 tesla magnet. Areas of interest included the sensorimotor cortex (SMC), primary motor area (M1), primary sensory area (S1), premotor cortex (PMC) and supplementary motor area (SMA). Comparison between all subjects with stroke and all well elderly subjects at pre-test was analysed with two-sample t-tests. Change from pre-test to post-test within subjects was analysed with paired t-tests. Statistical significance was set at P < 0.05. Stroke treatment subjects demonstrated significant improvement in tracking accuracy, whereas stroke control subjects did not until after crossover treatment. At pre-test, the cortical activation in the subjects with stroke was predominantly ipsilateral to the performing hand, whereas in the well elderly subjects it was contralateral. Activation for the stroke treatment group following training switched to contralateral in SMC, M1, S1 and PMC. The stroke control group's activation remained ipsilateral after the control period, but switched to contralateral after crossover to receive treatment. All well elderly subjects maintained predominantly contralateral activation throughout. Transfer of skill to functional activity was shown in significantly improved Box and Block scores for the stroke treatment group, with no such improvement in the stroke control group until after crossover. We concluded that individuals with chronic stroke receiving intensive tracking training showed improved tracking accuracy and grasp and release function, and that these improvements were accompanied by brain reorganization.

The use of a pressure manometer enhances student physiotherapists' performance during manual hyperinflation

The purpose of this study was to determine the effect of using a pressure manometer on the delivery of target airway pressures during manual hyperinflation by student physiotherapists in the laboratory and clinical environments. Manual hyperinflations were delivered under control and feedback conditions where the feedback condition involved manual hyperinflation with a pressure manometer. Compared with control conditions, the availability of a manometer significantly decreased the mean absolute error (9.5 +/- 0.9 cm H2O to 1.4 +/- 0.2 cm H2O) and mean variable error (2.2 +/- 0.3 cm H2O to 1.3 +/- 0.1cm H2O) of peak airway pressures during manual hyperinflation. In addition, the availability of a manometer negated the influence of environment on accuracy. Therefore, the availability of a pressure manometer provided an effective clinical tool that was easily used to provide feedback regarding the peak airway pressures delivered during manual hyperinflation.

Augmented feedback reduces jump landing forces

STUDY DESIGN

Randomized, experimental design using a 1-way ANCOVA to determine the influence of various forms of feedback on jump landing forces.

OBJECTIVE

To investigate the effects of augmented feedback versus sensory feedback on the reduction of jump landing forces.

BACKGROUND

Several investigators have reported an increased risk of lower extremity injury associated with landing from a jump.

METHODS AND MEASURES

Nonimpaired college students (N=63) were randomly assigned to 1 of 4 feedback groups. Subjects were instructed to perform maximal vertical jumps onto a force plate for 3 testing sessions (baseline, 2-minute post-test, and 1-week post-test). Three feedback groups (augmented, sensory, and control I) were tested during all 3 testing sessions, while a fourth feedback group (control II) was evaluated at only 2 sessions (baseline and 1-week post-test). Subjects in the augmented feedback condition were provided information via video and verbal analysis of how to land softer. Subjects in the sensory feedback condition were asked to use the experience of their baseline jumps to document how they could land softer. Subjects in each of the control groups were not provided any extraneous feedback. Peak vertical ground reaction force data were collected for analysis.

RESULTS

The subjects in the augmented feedback group significantly reduced their peak vertical ground reaction force in both post-test conditions (2-minute post-test reduction, 0.85+/-0.62; 1-week post-test reduction, 0.74+/-0.58) as compared to the sensory, control I, and control II feedback groups.

CONCLUSIONS

High impact landing forces may be reduced by the implementation of augmented feedback information instructing individuals about how to land properly. The reduction of jump landing forces with the use of augmented feedback may prove beneficial in the creation of instructional landing programs.

Knowledge of results for motor learning: relationship between error estimation and knowledge of results frequency

The authors of the present study investigated the apparent contradiction between early and more recent views of knowledge of results (KR), the idea that how one is engaged before receiving KR may not be independent of how one uses that KR. In a 2 &times: 2 factorial design, participants (N = 64) practiced a simple force-production task and (a) were required, or not required, to estimate error about their previous response and (b) were provided KR either after every response (100%) or after every 5th response (20%) during acquisition. A no-KR retention test revealed an interaction between acquisition error estimation and KR frequencies. The group that received 100% KR and was required to error estimate during acquisition performed the best during retention. The 2 groups that received 20% KR performed less well. Finally, the group that received 100% KR and was not required to error estimate during acquisition performed the poorest during retention. One general interpretation of that pattern of results is that motor learning is an increasing function of the degree to which participants use KR to test response hypotheses (J. A. Adams, 1971; R. A. Schmidt, 1975). Practicing simple responses coupled with error estimation may embody response hypotheses that can be tested with KR, thus benefiting motor learning most under a 100% KR condition. Practicing simple responses without error estimation is less likely to embody response hypothesis, however, which may increase the probability that participants will use KR to guide upcoming responses, thus attenuating motor learning under a 100% KR condition. The authors conclude, therefore, that how one is engaged before receiving KR may not be independent of how one uses KR.

The effects of different knowledge of results spacing and summarizing techniques on the acquisition of a ballistic movement

The present study crossed three knowledge of results summarizing techniques (single-trial KR, summary KR, and average KR) with two spacing conditions (KR on every fifth trial-20%- and KR on every trial-100%). Participants (n = 10 per group) performed 80 acquisition trials of a ballistic movement task involving both a temporal and spatial goal, followed by 30 immediate (10 min) and 30 delayed (2 days) no-KR transfer trials. For the spatial goal, performance was less accurate (absolute constant error) for the 20% spacing condition than the 100% condition during acquisition, but more accurate during delayed transfer. No effects were significant for variable error. For the temporal goal, performance was more accurate for the summary and average conditions than the single-trial KR condition; however, this effect was only present within the 20% spacing condition and only during Block 1 of acquisition. A similar effect held for variable error as well, except that the effect persisted for acquisition and transfer. It was concluded that the spacing of KR is more influential in promoting spatial accuracy than the summarizing of KR.

Optimal length for summary knowledge of results: the influence of task-related experience and complexity

Because manipulations of knowledge of results (KR) are critical to motor learning, researchers have attempted to establish an optimal length for summary KR. Experiment 1 of the present study investigated the option that optimal summary length may be dependent on a subject's task-related experience. Participants in a summary 1, 5, or 15 condition practiced a simple striking task for one session on three consecutive days with each day followed by a 24-hour no KR retention test. The retention test results indicated that optimal summary length is dependent on task-related experience. Experiment 2 investigated the nature of the relationship between task-related experience and complexity and optimal summary length (summary 1, 5, or 15). Again, striking tasks (simple and complex) were used. There was one practice session with either a simple or complex striking task for either novice or experienced performers, followed by a 24-hour no KR retention test. Data from the two experiments suggest that task complexity and performer experience interact in determining optimal summary length.

Augmented feedback for enhanced skill acquisition in individuals with traumatic brain injury

Coincident timing by individuals who exhibit traumatic brain injury was measured under conditions of no knowledge of results (no KR; n = 12), KR on every trial (n = 14), summary KR (n = 13), and average KR (n = 12). Following acquisition trials, groups performed immediate and longer retention trials without KR. Absolute constant error and variable error, analyzed in separate repeated-measures analyses of variance, indicated that during acquisition trials subjects receiving KR on every trial were the most accurate and the most consistent in their responses; however, subjects in groups receiving summary and average KR were the most accurate during immediate retention, with the group receiving summary KR being the most accurate during longer retention.