Win-Shift, Lose-Stay: Contingent Switching and Contextual Interference in Motor Learning

High contextual interference improves retention in motor learning: systematic review and meta-analysis

The effect of practice schedule on retention and transfer has been studied since the first publication on contextual interference (CI) in 1966. However, strongly advocated by scientists and practitioners, the CI effect also aroused some doubts. Therefore, our objective was to review the existing literature on CI and to determine how it affects retention in motor learning. We found 1255 articles in the following databases: Scopus, EBSCO, Web of Science, PsycINFO, ScienceDirect, supplemented by the Google Scholar search engine. We screened full texts of 294 studies, of which 54 were included in the meta-analysis. In the meta-analyses, two different models were applied, i.e., a three-level mixed model and random-effects model with averaged effect sizes from single studies. According to both analyses, high CI has a medium beneficial effect on the whole population. These effects were statistically significant. We found that the random practice schedule in laboratory settings effectively improved motor skills retention. On the contrary, in the applied setting, the beneficial effect of random practice on the retention was almost negligible. The random schedule was more beneficial for retention in older adults (large effect size) and in adults (medium effect size). In young participants, the pooled effect size was negligible and statically insignificant.

Interactive curriculum learning increases and homogenizes motor smoothness

One of the challenges of technology-assisted motor learning is how to adapt practice to facilitate learning. Random practice has been shown to promote long-term learning. However, it does not adapt to the learner's specific learning requirements. Previous attempts to adapt learning considered the skill level of learners from past training sessions. This study investigates the effects of personalizing practice in real time, through a curriculum learning approach, where a curriculum of tasks is built by considering consecutive performance differences for each task. 12 participants were allocated to each of three training conditions in an experiment which required performing a steering task to drive a cursor in an arc channel. The curriculum learning approach was compared to two other conditions: random practice and another adaptive practice, which does not consider the learning evolution. The curriculum learning practice outperformed the random practice in effectively increasing movement smoothness at post-test and outperformed both the random practice and the adaptive practice on transfer tests. The adaptation of practice through the curriculum learning approach also made learners' skills more uniform. Based on these findings, we anticipate that future research will explore the use of curriculum learning in interactive training tools to support motor skill learning, such as rehabilitation.

A scoping review of the application of motor learning principles to optimize myoelectric prosthetic hand control

Although prosthetic hand rejection rates remain high, evidence suggests that effective training plays a major role in device acceptance. Receiving training early in the rehabilitation process also enhances functional prosthetic use, decreases the likelihood of developing an overreliance on the intact limb, and reduces amputation-related pain. Despite these obvious benefits, there is a current lack of evidence regarding the most effective training techniques to facilitate myoelectric prosthetic hand control, and it remains unknown whether training is effective in facilitating the acquisition and transfer of prosthetic skill. In this scoping review, we introduced and summarized key motor learning principles related to attentional focus, implicit motor learning, training eye-hand coordination, practice variability, motor imagery, and action observation, and virtual training and biofeedback. We then reviewed the existing literature that has applied these principles for training prosthetic hand control before outlining future avenues for further research. The importance of optimizing early and appropriate training cannot be overlooked. While the intuition and experience of clinicians holds enormous value, evidence-based guidelines based on well-established motor learning principles will also be crucial for training effective prosthetic hand control. While it is clear that more research is needed to form the basis of such guidelines, it is hoped that this review highlights the potential avenues for this work.

Contextual Interference Effects on Approach Motivation When Learning Timing Tasks: A Frontal Electroencephalography (EEG) Alpha Asymmetry Study in Older Adults

In this study, we aimed to explore the effects of contextual interference on motivational regulation, as measured by EEG (frontal alpha asymmetry), in older adults. Participants practiced a sequenced timing task in random, algorithmic, or blocked schedules in both similar and dissimilar task difficulty conditions, with task difficulty defined by absolute timing goals (in ms) that were either close to each other (1350, 1500, 1650) or far from each other (1050, 1500, 1950), respectively. We assessed older participants' timing accuracy in these conditions, during acquisition and delayed retention learning, using the frontal alpha asymmetry index, recorded during practice, to measure motivation. On the accuracy measure in delayed retention, the algorithm practice schedule (in both similar and dissimilar conditions) was associated with significantly more accurate performance than random and blocked practice schedules. Also during delayed retention and in both task difficulty conditions, performance was better with a random schedule than a blocked schedule. On the EEG motivational measure, frontal alpha asymmetry was more often higher as practice progressed in the algorithm practice condition than in other practice conditions. However, in the random practice schedule, in late, versus early, acquisition, motivational regulation was higher. The blocked groups showed decreased motivation as practice progressed. We interpreted these findings to be in accordance with the challenge point framework and with OPTIMAL motor learning theory and valence hypothesis.

"You're wrong, I'll switch, I'm wrong, I'll stay": How task-switching strategies are modulated by a partner in a multi-task learning protocol

Individuals given control over practice variables make practice decisions based on their current performance. When individuals practice in pairs, the question as to if and how a partner's performance impacts these decisions is of theoretical and practical interest. Here, we evaluated this question in a multi-task learning protocol, where individuals and dyads practiced three, differently timed keystroke sequences. Dyad participants alternated turns with a partner so we could study the immediate consequences of the partner's performance on practice choice. Only one of the partners had choice over the sequence order, the other partner practiced the sequences in either a predetermined blocked or random order. Practice with a partner that had a random-schedule promoted more task-switching in the other partner and had some benefit for retention accuracy. Distinct "own-error" and "partner-error" switching strategies were evidenced, with partners choosing to repeat the same sequence on their next turn when they performed poorly or when their partner performed well. These data show that an individual's practice decisions are influenced by their social context, particularly the practice schedule and patterns of errors in a partner's performance.

Now you see me, now you don't: Adapting practice through target exclusion negatively impacts motor learning

How to optimize practice through scheduling of different task components or skills is a question that has received a lot of attention in motor learning research. Consistently, schedules with high variability in the order that skills are practiced elicit better learning outcomes than schedules with low variability. Another idea is that learners should seek to reduce the uncertainty of practice outcomes, by avoiding well-learned, low error components in acquisition. To test this idea, we used a target exclusion method to prevent learners from returning to task components with low error and studied how individuals given choice over practice choose to allocate time to components of varying difficulty. In a multi-target adaptation paradigm, we compared exclusion with no exclusion methods in random-schedule, self-control and yoked, matched-schedule groups (6 groups total). To manipulate uncertainty, we excluded targets from practice once participants attained a criterion error score (mean < 5^o) from the last 5 trials to the same target. Contrary to our predictions, groups that practiced without target exclusion were more accurate in retention compared to exclusion groups; irrespective of practice schedule. Self-control groups adopted uncertainty-based practice, spending more time at difficult targets and less time at easier targets. However, there were no group differences in error, based on schedule-type (random, self-control and yoked). In conclusion, target exclusion was not an effective method for learning and did not support the efficacy of uncertainty-based practice for learning novel skills. There were benefits from keeping easier/low error skills in practice for later retention. These benefits did not appear to be related to the increased switching between skills, but could be related to increased task engagement and more optimal challenge associated with practice on a range of target difficulties, rather than the most difficult.

Algorithm-Based Practice Schedule and Task Similarity Enhance Motor Learning in Older Adults

According to the challenge point framework, task difficulty has to be appropriate to learner skill level. The pure blocked or random practice controls the task difficulty during practice monotonically. Therefore, the purpose of this study was to investigate the effect of algorithm-based practice schedule and task similarity on motor learning in older adults. For this purpose, 60 older adults were randomly assigned into six groups of blocked-similar, algorithm-similar, random-similar, blocked-dissimilar, algorithm-dissimilar, and random-dissimilar. Sequential motor tasks were used for learning. Participants practiced absolute timing goals in similar (1350, 1500, 1650 ms) or dissimilar (1050, 1500, 1950 ms) conditions according to their practice schedule. Twenty-four hours after the acquisition phase, retention, and transfer tests were performed. Algorithm-practice was a hybrid practice schedule (blocked, serial, and random practice in forward/backward switching) that switching the schedules was according to error trial number (n ≤ 33%) in each block based on error range of absolute timing goals (± 5%). The results showed that the blocked-practice outperforms the other groups during the acquisition phase, whereas the algorithm-practice outperforms the other groups in retention and transfer in both similar and dissimilar conditions. These findings were discussed according to the challenge point framework.

Neural Mechanisms of the Contextual Interference Effect and Parameter Similarity on Motor Learning in Older Adults: An EEG Study

The purpose of this study was to investigate the neural mechanisms of the contextual interference effect (CIE) and parameter similarity on motor learning in older adults. Sixty older adults (mean age, 67.68 ± 3.95 years) were randomly assigned to one of six experimental groups: blocked-similar, algorithm-similar, random-similar, blocked-dissimilar, algorithm-dissimilar, and random-dissimilar. Algorithm practice was a hybrid practice schedule (a combination of blocked, serial, and random practice) that switching between practice schedules were based on error trial number, ≤33%. The sequential motor task was used to record the absolute timing for the absolute timing goals (ATGs). In similar conditions, the participants’ performance was near ATGs (1,350, 1,500, 1,650 ms) and in dissimilar conditions, they performed far ATGs (1,050, 1,500, 1,950 ms) with the same spatial sequence for all groups. EEG signals were continuously collected during the acquisition phase and delayed retention. Data were analyzed in different bands (alpha and beta) and scalp locations (frontal: Fp1, Fp2, F3, F4; central: C3, C4; and parietal: P3, P4) with repeated measures on the last factor. The analyses were included motor preparation and intertrial interval (motor evaluation) periods in the first six blocks and the last six blocks, respectively. The results of behavioral data indicated that algorithm practice resulted in medium error related to classic blocked and random practice during the acquisition, however, algorithm practice outperformed the classic blocked and random practice in the delayed retention test. The results of EEG data demonstrated that algorithm practice, due to optimal activity in the frontal lobe (medium alpha and beta activation at prefrontal), resulted in increased activity of sensorimotor areas (high alpha activation at C3 and P4) in older adults. Also, EEG data showed that similar conditions could affect the intertrial interval period (medium alpha and beta activation in frontal in the last six-block), while the dissimilar conditions could affect the motor preparation period (medium alpha and beta activation in frontal in the first six-block). In conclusion, algorithm practice can enhance motor learning and optimize the efficiency of brain activity, resulting in the achievement of a desirable goal in older adults.

Learner-adapted practice promotes skill transfer in unskilled adults learning the basketball set shot

The current study used a complex, sport-specific movement skill to explore the effects of a win-shift/lose-stay practice schedule on learning and compared its effectiveness with that of blocked and random practice schedules. Thirty-six adults (24.9 ± 3.3 years) were assigned to blocked, random and learner-adapted training groups. Each participant performed 360 trials of the basketball set shot from multiple locations across six practice sessions. For the learner-adapted group, switching between task variations was performance-contingent; switching between shooting locations occurred only following a successful shot. Shooting success was calculated as the percentage of successful shots performed, and measured during pre-acquisition (i.e. baseline), acquisition (i.e. practice) and post-acquisition (i.e. retention and transfer). Despite scoring less shots throughout practice compared to baseline testing, the learner-adapted group showed a significant improvement for shooting success in transfer (d = 1.02). Blocked practice demonstrated significant improvements for shooting success in immediate retention (d = 1.83), delayed retention (d = 1.69) and transfer (d = 1.39). Random practice significantly improved shooting success in both immediate (d = 1.03) and delayed retention (d = 0.81). The current findings highlight that performance during practice does not necessarily represent the permanency and adaptability of skill learning. The implications of the findings and their practical applications are discussed in the context of practice scheduling during learning of a sports skill.

Individualized Challenge Point Practice as a Method to Aid Motor Sequence Learning

We conducted two studies to investigate if and how: (1) the rate of skill acquisition was related to motor performance at retention of a serial RT task (Study 1); and (2) whether rate of skill acquisition and baseline performance could be used to design schedules of practice related to contextual interference (CI) to enhance motor learning (Study 2). In Study 1, a slower rate of skill acquisition of repeating sequences in practice was related to faster response times at retention. Based on performance in Study 1, three levels of individualized CI were created for Study 2. Compared to low and moderate levels of CI, the higher CI practice condition led to faster response times in retention. We conclude that an individualized 'challenge point', which generates high CI enhances motor learning by optimizing challenge.

Quantifying Contextual Interference and Its Effect on Skill Transfer in Skilled Youth Tennis Players

The contextual interference effect is a well-established motor learning phenomenon. Most of the contextual interference effect literature has addressed simple skills, while less is known about the role of contextual interference in complex sport skill practice, particularly with respect to skilled performers. The purpose of this study was to assess contextual interference when practicing the tennis serve. Study 1 evaluated tennis serve practice of nine skilled youth tennis players using a novel statistical metric developed specifically to measure between-skill and within-skill variability as sources of contextual interference. This metric highlighted that skilled tennis players typically engaged in serve practice that featured low contextual interference. In Study 2, 16 skilled youth tennis players participated in 10 practice sessions that aimed to improve serving "down the T." Participants were stratified into a low contextual interference practice group (Low CI) and a moderate contextual interference practice group (Moderate CI). Pre- and post-tests were conducted 1 week before and 1 week after the practice period. Testing involved a skill test, which assessed serving performance in a closed setting, and a transfer test, which assessed serving performance in a match-play setting. No significant contextual interference differences were observed with respect to practice performance. However, analysis of pre- and post-test serve performance revealed significant Group × Time interactions. The Moderate CI group showed no change in serving performance (service displacement from the T) from pre- to post-test in the skill test, but did display improvements in the transfer test. Conversely, the Low CI group improved serving performance (service displacement from the T) in the skill test but not the transfer test. Results suggest that the typical contextual interference effect is less clear when practicing a complex motor skill, at least with the tennis serve skill evaluated here. We encourage researchers and applied sport scientists to use our statistical metric to measure contextual interference.

Exploring the applicability of the contextual interference effect in sports practice

This review will consider three key issues considered critical when determining the efficacy of the contextual interference effect when applied to sports practice. First, the issue of complexity is considered in relation to the amount of interference actually needed in the applied sports setting to create effective learning. Second, the traditional underpinning mechanism/s of contextual interference are discussed in relation to recent neurophysiological perspectives on their viability. A counter-position to these dominant theories is also presented drawing on an implicit learning framework. The final issue considers the typical measures of learning used within the contextual interference literature and scrutinizes them relative to the needs of bridging the apparent theory-practice divide. The concluding section then presents a model to measure the degree of contextual interference within the applied setting, which in turn offers both future research directions as well as guidelines for practitioners.

Absence of equifinality of hand position in a double-step unloading task

Equifinality, during arm reaching movements, relates to the capacity of the neuromuscular system to attain the same final position in the presence or absence of transient perturbations. There have been several controversies regarding equifinality in the literature. A brief elastic perturbation, applied during a fast arm movement or just before its initiation, typically does not affect final arm position. On the other hand, several experiments have shown that velocity-dependent perturbations, such as Coriolis force or negative damping, while transient in nature, have a significant effect on final arm position when compared to unperturbed movements. In this study, an unloading paradigm was used to study the role of reflexes with respect to equifinality. The effects on final arm position of suddenly decreasing a static load maintained by fourteen subjects were analyzed. Subjects maintained an initial load produced by a double-joint manipulandum moving in the horizontal plane. The load was suddenly decreased, either in one or in two successive steps with different time intervals, resulting in a rapid reflex-mediated change in arm position. Unloading led to short-latency changes in the activity of shoulder and elbow muscles and significant variations in tonic activity. It was found that the final hand position was shorter for double- versus single-step unloading if the time between two successive changes in load was greater than 100 ms. With a shorter time interval, the final hand positions were the same. This difference in final hand positions was inversely proportional to the hand velocity at the time of the second change in load. Further, agonist/antagonist co-activation increased in double-step unloading. Thus, the change in both the load and the movement velocity may influence the magnitude of the unloading reflex. This may be indicative of a dependence of stretch reflexes on velocity. Perturbation may cause a reflex-mediated increase in joint stiffness, which could explain why equifinality is not preserved after some perturbations, such as velocity-dependant external forces.