Variable Practice Conditions Research Articles

Promoting Exploration During Learning: Effect of Imposed and Self-Controlled Practice Schedules on Learners’ Behavioral Flexibility

ABSTRACT Purpose: Enriching learners’ motor repertoires in a complex pluri-articular task, such as climbing, could help learners’ adaptation to various sets of task constraints. Promoting exploration with variable practice conditions is one solution recurrently proposed. However, recent studies have shown that a too elevated exploration-exploitation ratio during practice could impair learning. A proposed solution is to give learners some control over their practice schedule, which appeared to better respect the individual learning dynamic in comparison to the usual experimenter-imposed practice schedule. Thus, the aim of this study is to investigate whether giving learners the possibility of controlling when to confront to new climbing routes would result in greater flexibility in their motor repertoire compared to giving them an imposed schedule of climbing routes or a constant practice condition. Method: Participants were assigned to either a constant practice group (CPG), an imposed-variability group (IVG) or a self-controlled variability group (SVG) to carry out a climbing task. To assess participants’ behavioral flexibility, a scanning procedure was conceived by manipulating the route design and the instructions. Results: Participants showed an initial lack of flexibility as they strongly relied on a single coordination pattern. At posttest and retention, the three groups more frequently used a new hand coordination pattern and more often showed coordination patterns associated with high climbing fluency. Results suggest that the individualized rate of exploration in the self-controlled practice condition may have helped the learners improve their flexibility, whereas forcing exploration did not seem more beneficial than constant practice in this complex pluri-articular task.

Enhancing Executive Function in Children and Adolescents Through Motor Learning: A Systematic Review

Enhancing executive function in children and adolescents can have significant positive impact on their current and future daily lives. Upregulation of executive function associated with motor skill acquisition suggests that motor learning scenarios provide valuable developmental opportunities to optimize executive function. The present systematic review aimed to identify key motor learning features that contribute to executive function enhancement in children and adolescents. A January 2024 database search identified 62 eligible studies, involving a total of 4,163 children and adolescents, aged 3–17 years, from developmentally typical (35 studies) and atypical or clinical (27 studies) populations. Schools (51%), sports (22%), laboratory (11%), or home (5%) settings with 8- to 12-week programs for primarily fundamental or perceptual-motor skills but also sport, dance, and musical instrument skills were implemented to evaluate executive function outcomes in domains including working memory (55%), inhibitory control (55%), attention (48%), and cognitive flexibility (41%). Enhanced executive function was most frequently associated with gross and discrete or serial motor skill characteristics, closed or stationary regulatory environments, and variable practice conditions. Studies frequently omitted the assessment of motor learning outcomes or lacked sufficient methodological detail needed to classify motor skill and practice design features that might contribute to executive function enhancement.

Motor-cognitive exercise with variability of practice and feedback improves functional ability and cognition in older individuals.

Motor-cognitive dual-task training seems the most favorable form of exercise for functional and cognitive improvements in older individuals. The optimal exercise regime is still uncertain, and the potential benefits of qualitative parameters of exercise prescription such as feedback provision and practice variability are mostly unknown. To verify the effects of a motor-cognitive dual-task training with feedback provision and variability of practice for improving functional ability and cognition in older individuals. Thirty individuals (3 men) aged over 65years were tested on walking speed, static and dynamic balance, lower limb strength, and cognition before and after a 5-week motor-cognitive intervention. Training consisted of twice weekly, 30min gross-motor coordination exercises with variable practice conditions combined with stimulus-response cognitive tasks generated by an interactive device. Participants were divided into an experimental group and a control group, respectively receiving and nonreceiving feedback during training. A 2 × 2 ANOVA was used to verify the effects of training. Both groups improved static and dynamic balance (p < 0.05), walking speeds (p < 0.05), lower limb strength (p < 0.05) and cognitive functions with greater gains observed in the experimental group (p < 0.01). Variability of practice applied to motor-cognitive dual-task training is effective for improving, in only 5 weeks, functional ability and cognitive processing in older individuals. These changes were possibly afforded through motor and cognitive enhancement induced by exercise complexity. Provision of feedback seems to particularly benefit cognitive functions. Brief motor-cognitive dual-task training using practice variability and feedback seems effective for counteracting the age-related cognitive and functional decline.

Exploring in a climbing task during a learning protocol: a complex sense-making process.

In perceptual-motor learning, constant and variable practice conditions have been found to have differential effects on learners' exploratory activity and their ability to transfer their skills to novel environments. However, how learners make sense of these practice conditions during practice remains unclear. This study aimed to analyse learners' experiences of different practice conditions during a climbing learning protocol and to examine how these experiences might further inform learners' exploratory activity. Twelve participants assigned to either 'Constant practice', 'Imposed Novelty', or 'Chosen novelty' groups climbed a 'Control route' (i.e. a route common to all groups) and a 'transfer route' (i.e. a new route) before and after a ten session learning protocol. Descriptions of learners' experiences during previews and climbs were collected using self-confrontation interviews. After identifying general dimensions via a thematic analysis, a hierarchical cluster analysis on these general dimensions allowed the identification of phenomenological clusters (PhC). The distribution of these PhCs was compared between the first and last learning sessions, the control and transfer routes, and the practice condition groups. We identified seven PhCs reflecting learners' meaningful exploratory activity during the previews and climbs. Significant differences in the distribution of these PhCs were found between (i) the first and the last session, (ii) the control and the transfer route and (iii) the Chosen-novelty group and the other two practice groups. These results suggest that exploration is part of a complex sense-making process linked to practice conditions, which can be described by a joint analysis of the intentions, perceptions and actions.

Neuroplasticity in Motor Learning Under Variable and Constant Practice Conditions-Protocol of Randomized Controlled Trial.

BackgroundThere is numerous literature on mechanisms underlying variability of practice advantages. Literature includes both behavioral and neuroimaging studies. Unfortunately, no studies are focusing on practice in constant conditions to the best of our knowledge. Hence it is essential to assess possible differences in mechanisms of neuroplasticity between constant vs. variable practice conditions. The primary objectives of the study described in this protocol will be: (1) to determine the brain’s structural and functional changes following constant and variable practice conditions in motor learning (structural and functional magnetic resonance imaging, MRI); (2) to determine the EEG activation and connectivity between cognitive, sensory, and motor cerebral cortex areas (central, temporal, parietal, occipital) in constant and variable practice conditions and as a function of practice time.MethodsThe study will follow the interventional (experimental) design with two arms (parallel groups). Fifty participants will be randomly assigned to two groups practicing in constant (CG) and variable conditions (VG). CG will be practicing only one pattern of step isometric contractions during unimanual index finger abduction, i.e., 90 trials in all training sessions, whereas VG will practice three different patterns. Each will be practiced 30 times per session in variable conditions. Resting-state fMRI, EEG (cortical networking), and motor task proficiency will be examined before (pre-) and after practice (post- and retentions tests).DiscussionFindings will enhance our understanding of structural and functional neural changes following practice in constant and variable conditions. Therefore, the study can be considered pure (basic) research (clinical research in healthy individuals).Clinical Trial RegistrationStudy registered at clinicaltrials.gov (ID# NCT04921072) on 9 June 2021. Last version update: 21 December 2021.The protocol has been prepared according to the complete SPIRIT checklist (http://www.spirit-statement.org/), although the item order has been modified in order to comply with the manuscript structure.

OpenEar Image Data Enables Case Variation in High Fidelity Virtual Reality Ear Surgery.

Virtual reality (VR) simulation is an established option for temporal bone surgical training. Most VR simulators are based on computed tomography imaging, whereas the Visible Ear Simulator (VES) is based on high-fidelity cryosections of a single temporal bone specimen. Recently published OpenEar datasets combine cone-beam computed tomography (CBCT) and micro-slicing to achieve similar model quality. This study explores integration of OpenEar datasets into VES to enable case variation in simulation with implications for patient-specific modeling based on CBCT. The OpenEar dataset consists of segmented, coregistered, multimodal imaging sets of human temporal bones. We derived drillable bone segments from the dataset as well as triangulated surface models of critical structures such as facial nerve or dura. Realistic visualization was achieved using coloring from micro-slicing, custom tinting, and texture maps. Resulting models were validated by clinical experts. Six of the eight OpenEar datasets could be integrated in VES complete with instructional guides for various temporal bone surgical procedures. Resulting models were of high quality because of postprocessing steps taken to increase realism including colorization and imaging artifact removal. Bone artifacts were common in CBCT, resulting in dehiscences that most often could not be found in the ground truth micro-slicing data. New anatomy models are included in VES version 3.5 freeware and provide case variation for training which could help trainees to learn more quickly and transferably under variable practice conditions. The use of CBCT for VR simulation models without postprocessing results in bone artifacts, which should be considered when using clinical imaging for patient-specific simulation, surgical rehearsal, and planning.

Variability of Practice, Information Processing, and Decision Making-How Much Do We Know?

Decision-making is a complex action requiring efficient information processing. Specifically, in movement in which performance efficiency depends on reaction time, e.g., open-loop controlled movements, these processes may play a crucial role. Information processing includes three distinct stages, stimulus identification, response selection, and response programming. Mainly, response selection may play a substantial contribution to the reaction time and appropriate decision making. The duration of this stage depends on the number of possible choices an individual has to “screen” to make a proper decision. Given that reaction time is crucial in many sports, the possibilities of reducing it through practice are very tempting. The information processing and its relationship to the manner an individual is practicing are discussed. Especially the variability of practice issues will be explored. In variable practice conditions, an individual has to react to one or more stimuli and has to produce one of the many variations of the same movement or different movements they learned. One has to identify a stimulus appropriately and has to select a response optimally, i.e., choosing from as few choices as possible to reduce the reaction time. On the other hand, in constant practice conditions, an individual can be exposed to one or many stimuli. Still, there is only one variation of the movement that can be executed in the presence of a learned stimulus. Based on the information processing theory and the results of the research focusing on variability of practice, I discuss how the practice conditions may affect reaction time and, as a result, the decision-making process. I conceptually frame the possible implications of practice conditions on decision making related to information processing. In this review, a possible mechanism and relationship between practice conditions and decision-making are presented. Future research directions are presented.

Utilizing the Variability of Practice in Physical Execution, Action Observation, and Motor Imagery: Similar or Dissimilar Mechanisms?

The simulation theory argues that physical execution, action observation, and imagery share similar underlying mechanisms. Accordingly, applying a high-level psychological variable (variability of practice) should have a similar effect on all three modes. To test this theory, a total of 90 right-handed students participated in this study and were randomly divided into variable versus constant groups in three practice conditions, including physical, observational, and imagery. After a pretest (10 random trials of the putting task), the participants completed 50 practice trials. The groups performed/observed/imagined the task in the variable (different distances to different goals) or constant (fixed distance and goal) practice conditions. Also, there was an extra variable group in the physical and observational conditions, deprived of watching the feedback from the action. The participants completed a retention test 24hr after the training. The effect of practice variability was observed in physical and observational conditions, but was not seen in the imagery condition. The no-feedback groups did not perform significantly differently from the imagery groups. The reason could be the lack of actual visual feedback during imagery.

The Development of Generalized Motor Program in Constant and Variable Practice Conditions.

The main objective of our study was to determine whether constant and variable practice conditions lead to the development of different memory representations (GMP) and as a result, they benefit performance of a skill differently. We compared one of the Generalized Motor Program (GMP) invariant features, i.e., relative timing, of the same variation of skill developed in constant and variable practice conditions. In two experiments, participants, naïve to the basketball, were practicing free throws, receiving the same amount of practice. In constant conditions they practiced at one distance only (4.57 m), whereas in variable conditions they practiced at seven (2.74, 3.35, 3.96, 4.57, 5.18, 5.79, and 6.4 m) and five (3.35, 3.96, 4.57, 5.18, and 5.79 m) distances, in Experiments 1 and 2, respectively. We found that relative timing of skills developed in constant and variable practice conditions is the same, confirming that these practice conditions form the same memory representation. However, we also observed that constant practice (CP) conditions resulted in overall shorter movement time as compared to the skill practiced in variable conditions. We hypothesized that it may be due to the facilitation of parameters assignment as it takes place in especial skill.

Gaze Behavior in Basketball Free Throws Developed in Constant and Variable Practice.

There are a limited number of studies focusing on the mechanisms explaining why variable practice gives an advantage in a novel situation and constant practice in performance in trained conditions. We hypothesized that this may be due to the different gaze behavior that is developed under different conditions. Twenty participants, randomly assigned to two different groups, practiced basketball free throws for three consecutive days, performing 100 throws per day. The constant group (n = 10) practiced at a free throw distance (4.57 m) only. The variable practice group (n = 10) randomly performed 20 shots per five throw distances (3.35, 3.96, 4.57, 5.18, and 5.79 m) on each day, also accumulating 100 shots per day. We analyzed the total gaze fixation duration, a number of fixations, and the average fixation duration on a basketball rim in a pretest and posttest at the 4.57 m distance. We computed a linear mixed model with test (pretest–posttest), group (constant–variable), and test × group interaction in order to analyze the total fixation duration and number of fixations. The average fixation duration was analyzed with a repeated measure two-way ANOVA, with practice conditions as a between-participants factor and test type as a within-participants factor. We found that the total fixation duration increased significantly in the posttest, regardless of the practice conditions (p < 0.001, effect size = 0.504). The number of fixations also increased significantly in the posttest (p = 0.037, effect size = 0.246). The average fixation duration increased in both groups; however, insignificantly. We also did not find any significant differences between groups. Our results suggest that variable and constant practice conditions may lead to the development of similar gaze behavior.

Contextual Interference Effect Is Independent of Retroactive Inhibition but Variable Practice Is Not Always Beneficial.

Positive effects of variable practice conditions on subsequent motor memory consolidation and generalization are widely accepted and described as the contextual interference effect (CIE). However, the general benefits of CIE are low and these benefits might even depend on decreased retest performances in the blocked-practicing control group, caused by retroactive inhibition. The aim of this study was to investigate if CIE represents a true learning phenomenon or possibly reflects confounding effects of retroactive inhibition. We tested 48 healthy human participants adapting their reaching movements to three different force field magnitudes. Subjects practiced the force fields in either a Blocked (B), Random (R), or Constant (C) schedule. In addition, subjects of the Blocked group performed either a retest schedule that did (Blocked-Matched; BM) or did not (Blocked-Unmatched; BU) control for retroactive inhibition. Results showed that retroactive inhibition did not affect the results of the BU group much and that the Random group showed a better consolidation performance compared to both Blocked groups. However, compared to the Constant group, the Random group showed only slight benefits in its memory consolidation of the mean performance across all force field magnitudes and no benefits in absolute performance values. This indicates that CIE reflects a true motor learning phenomenon, which is independent of retroactive inhibition. However, random practice is not always beneficial over constant practice.

Motor Learning of Gross-Motor Skills under Variable Practice Conditions

Research background and hypothesis. For both the athlete and the coach, the purpose and goal of training is the same: to enhance performance. Research aim. This study investigated the effect of differential learning on basketball free throw and volleyball strike. Research methods. In the basketball experiment, in pre-, post- and retention test design, the free throw performance was measured (number of successful shots). Aiming to investigate transfer performance, jump shots were tested. In the volleyball experiment, movement variability during the strike was further increased by the application of an elastic constraint. The second intervention and quasi-control group trained under constant practice conditions. Ball velocity and accuracy were analysed with a constant and a variable test.Research results. No signifi cant differences were observed for either the free throw (p &gt; 0.05) or the transfer performance (p &gt; 0.05). However, a positive trend for the variable group was observed in the transfer situation. For the strike in volleyball, the differential learning group had a signifi cant advantage with respect to velocity in a variable test situation (p &lt; 0.05) whereas in the constant situation (p &gt; 0.05) and measurements for accuracy (p &gt; 0.05) it did not reveal similar results.Discussion and conclusions. In both experiments, the set variability leads to benefi ts in variable (transfer) situations. However, as a practical consequence, especially for constant situations, certain moderator variables such as training age or background in other sports or activities must be kept in mind to adjust the amount of external or intervention-induced variability.Keywords: differential learning, variability, adaptability, ball sports.

Learning a specific, individual and generalizable coordination function: evaluating the variability of practice hypothesis in motor learning.

Constant and variable practice conditions have been hypothesized to lead to different learning outcomes between them but similar within. However, experiments have found that within a constant practice condition, participants can show highly individual outcomes (i.e., coordination functions). Considering the contradictory evidence on the effects of variable practice, we tested the idea that measures of the individual learned outcome would be required to provide a full explanation for results in transfer tests rather than or in addition to the group task-related conditions on which individuals practiced. Twenty-four participants were divided into three groups with different practice conditions (constant, varied distance of the target, and varied angle of the target) and for 5days performed a task of throwing for precision to a target. Pre-, post-, and transfer tests were used to evaluate our hypothesis. The results showed that although the group measures could predict certain aspects of the transfer tests, the coordination function characteristics were required to show higher levels of explanatory power. This finding supports the view that learning involves a specific, individual and generalizable solution although there are aspects of learning that are specific to the condition of practice.

Practice and transfer of the frequency structures of continuous isometric force

The present study examined the learning, retention and transfer of task outcome and the frequency-dependent properties of isometric force output dynamics. During practice participants produced isometric force to a moderately irregular target pattern either under a constant or variable presentation. Immediate and delayed retention tests examined the persistence of practice-induced changes of force output dynamics and transfer tests investigated performance to novel (low and high) irregular target patterns. The results showed that both constant and variable practice conditions exhibited similar reductions in task error but that the frequency-dependent properties were differentially modified across the entire bandwidth (0–12Hz) of force output dynamics as a function of practice. Task outcome exhibited persistent properties on the delayed retention test whereas the retention of faster time scales processes (i.e., 4–12Hz) of force output was mediated as a function of frequency structure. The structure of the force frequency components during early practice and following a rest interval was characterized by an enhanced emphasis on the slow time scales related to perceptual–motor feedback. The findings support the proposition that there are different time scales of learning at the levels of task outcome and the adaptive frequency bandwidths of force output dynamics.

Gait dynamics following variable and constant speed gait training in individuals with chronic stroke

Variable practice may be beneficial for learning novel motor patterns. The purpose of this study was to determine the effect of a variable practice intervention during treadmill walking on the dynamic properties of gait. Using a counterbalanced design, 16 subjects with hemiparesis following chronic stroke performed 20min of treadmill walking in constant speed training (CST) and variable speed training (VST) conditions. The dynamic properties of the hip and knee sagittal plane angles for two minutes before (pre-data) and two minutes after (post-data) CST and VST were examined using detrended fluctuation analysis and sample entropy. A main effect for time was observed for sample entropy of the knee angle; no other differences were observed between the pre/post data for the CST or VST conditions. While variable practice conditions are intended to promote movement errors for improved learning, we were unable to detect immediate changes in movement variability as a function of practice condition following a single session of gait training for individuals post-stroke.

Imagined actions aren't just weak actions: Task variability promotes skill learning in physical practice but not in mental practice.

Early research on visual imagery led investigators to suggest that mental visual images are just weak versions of visual percepts. Later research helped investigators understand that mental visual images differ in deeper and more subtle ways from visual percepts. Research on motor imagery has yet to reach this mature state, however. Many authors have implicitly subscribed to the view that motor images are just weak versions of physical actions. We tested this view by comparing motor learning in variable practice conditions with motor learning in constant practice conditions when participants either physically or mentally practiced golf-putting. We found that physical and mental practice both resulted in significant learning but that variable practice was only better than constant practice when participants practiced physically. This outcome was not predicted by the hypothesis that motor imagery is just a weaker form of real-action experience.

The education of attention as explanation of variability of practice effects: Learning the final approach phase in a flight simulator.

The present study reports two experiments in which a total of 20 participants without prior flight experience practiced the final approach phase in a fixed-base simulator. All participants received self-controlled concurrent feedback during 180 practice trials. Experiment 1 shows that participants learn more quickly under variable practice conditions than under constant practice conditions. This finding is attributed to the education of attention to the more useful informational variables: Variability of practice reduces the usefulness of initially used informational variables, which leads to a quicker change in variable use, and hence to a larger improvement in performance. In the practice phase of Experiment 2 variability was selectively applied to some experimental factors but not to others. Participants tended to converge toward the variables that were useful in the specific conditions that they encountered during practice. This indicates that an explanation for variability of practice effects in terms of the education of attention is a useful alternative to traditional explanations based on the notion of the generalized motor program and to explanations based on the notions of noise and local minima.

Treating control of voicing in apraxia of speech with variable practice

Background: Apraxia of speech (AOS) is generally considered a phonetic‐motoric disorder. As such, it is reasonable to draw on the motor learning literature to develop interventions for improving articulation. The often cited problem of impaired voicing control is used to test the application of a variable practice approach to training skilled movements in AOS. It is predicted that variable practice—practising a behaviour over a range of possible values or contexts—increases accuracy and stability of a trained behaviour. This work was supported in part by a NIH‐NIDCD RO3 grant DC005698 to Kirrie Ballard, an American Speech Language Hearing Foundation Grant for New Investigators to Kirrie Ballard, and a San Diego State University Research Foundation Grant to Donald Robin. We thank Vanessa Doerscher for assistance with running participants, and Rebekah Abel, Valerie Flemmer, Skott Freedman, Denise Gordon, Ling‐Yu Guo, Elizabeth Lang, Michael Molley, Ydine Sandberg, and Vanessa Shaw for assistance with data analysis. Aims: The aims of the study were to test the influence of variable practice conditions on acquisition and long‐term maintenance of voiced and voiceless phonemes in words at the phrase/sentence level as well as on generalisation of treatment effects to phonemes of same and different manner. The protocol was tested on two individuals with moderate AOS, one of whom exhibited a concomitant moderate aphasia. Methods & Procedures: A single subject multiple baseline across‐subjects design was used to examine efficacy of treatment for improving control of voicing for three fricative/affricate phonemes (Participant 1) or three plosive phonemes (Participant 2). The training sets included two voiced phonemes and one voiceless phoneme, each presented in the initial position of 10 different words. This provided a range of voice onset times and a range of phonetic contexts for each target phoneme, thus providing the variable practice. The inclusion of a voiceless phoneme that was produced at a high level of accuracy during baseline was hypothesised to reduce the chance of overgeneralisation from voiced to voiceless phoneme production. Outcomes & Results: Consistent with predictions, participants demonstrated improved production of trained voiced phonemes and generalisation of treatment effects to untrained phonemes of same manner only. These effects were maintained up to 3 months post‐treatment. Results support training multiple fricatives or plosives in parallel in a variety of phonetic contexts (i.e., variable practice) as well as including a combination of voiced and voiceless phonemes in treatment to ensure maintenance of accurate voiceless phoneme production. Conclusions: Results from two participants, varying in overall communication impairment severity, provide promising evidence that a variable practice approach to retraining speech behaviours in AOS is effective. Specifically, this approach resulted in long‐term maintenance of treatment effects and generalisation of treatment effects to untrained phonemes within manner class. Just as importantly, it did not result in overgeneralisation of voicing to voiceless phonemes. Further testing is required before recommending general clinical application.

Consistent and Variable Practice Conditions: Effects on Relative and Absolute Timing

The authors conducted the present experiments to resolve the discrepancy between studies in which relative-timing learning has been found to be enhanced by consistent practice conditions and contextual interference experiments in which relative-timing learning has been found to be enhanced more by random practice than by blocked practice. There were 40 participants in Experiment 1 and 48 in Experiment 2. The results of Experiment 1 extended previous findings: The learning of the relative-timing pattern was systematically enhanced by the degree to which the practice conditions promoted movement consistency (constant > blocked > serial > random). Experiment 2 provided evidence that the discrepancy between the relative-timing effects in the 2 groups of studies was a product of the way in which relative-timing goals and feedback were presented. When the feedback was presented as segment times, random practice resulted in generally more stable relative-timing patterns during acquisition than blocked practice did. Thus, in both experiments, the learning of the relative-timing pattern was enhanced by more stable relative-timing conditions during acquisition. Absolute-timing learning, as indexed by the transfer tests, was enhanced by serial or random practice as compared with constant or blocked practice, and was relatively unaffected by feedback conditions directed at the relative-timing pattern. In terms of motor programming theory, those findings are taken as additional evidence for the disassociation of memories supporting generalized motor program (GMP) performance, as indexed by relative timing, and parameter performance, as indexed by absolute timing.

Contextual Interference and Motor Skill Learning in Alzheimer’s Disease

This study examined the acquisition, retention, and transfer of a gross motor skill, namely, tossing, in 84 moderate-to-severely demented patients with Alzheimer’s disease (AD) and 72 healthy elderly controls. To identify optimal learning strategies, participants received 10 weeks of training under 1 of 5 practice conditions: constant, variable-parameter, variable-program, variable-combined, or no training. Constant practice was the only training condition that significantly enhanced learning and near transfer in AD patients. In comparison, all 4 types of training facilitated acquisition and near transfer in the healthy controls, with variable-combined practice being the most beneficial. The superiority of the variable practice conditions in the healthy controls supports both Schmidt’s (1975) variability of practice hypothesis and contextual interference theory. The inability of AD patients to benefit from variable forms of practice suggests that these impaired individuals may have difficulty accessing and/or forming motor schemas.