The effects of the amount and variability of practice on the learning of a multi-segmented motor task

Use of variable online visual feedback to optimize sensorimotor coding and learning of a motor sequence

The present study characterized the impact of reliable and/or unreliable online visual feedback and their order of presentation on the coding and learning of a motor sequence. Participants practiced a 12-element motor sequence 200 times. During this acquisition phase, two groups received a single type (i.e., either reliable or unreliable) of online visual feedback, two other groups encountered both types of feedback: either reliable first then unreliable, or unreliable first then reliable. Delayed retention tests and intermanual transfer tests (visuospatial and motor) were administered 24 hours later. Results showed that varying the reliability of online visual information during the acquisition phase allowed participants to use different task coding modalities without damaging their long-term sequence learning. Moreover, starting with reliable visual feedback, replaced halfway through with unreliable feedback promoted motor coding, which is seldom observed. This optimization of motor coding opens up interesting perspectives, as it is known to promote better learning of motor sequences.

Motor learning in neurological rehabilitation

While most upper limb training interventions in neurological rehabilitation are based on established principles of motor learning and neural plasticity, recovery potential may be improved if the focus includes remediating an individual's specific motor impairment within the framework of a motor control theory. This paper reviews current theories of motor control and motor learning and describes how they can be incorporated into training programs to enhance sensorimotor recovery in patients with neurological lesions. An emphasis is placed on dynamical systems theory and the use of new technologies such as virtual, augmented and mixed reality applications for rehabilitation to facilitate learning.Implications for RehabilitationKinematic abundance allows the healthy nervous system to produce different combinations of joint rotations to perform a desired task.The structure of practice to improve the movement repertoire in rehabilitation should take into account the kinematic abundance of the system.Learning can be enhanced by varied practice with feedback about key movement elements.Virtual reality environments provide opportunities to manipulate the structure and schedule of practice and feedback.

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.

Toward a Model of Human Information Processing for Decision-Making and Skill Acquisition in Laparoscopic Colorectal Surgery

OBJECTIVE

To create a human information-processing model for laparoscopic surgery based on already established literature and primary research to enhance laparoscopic surgical education in this context.

DESIGN

We reviewed the literature for information-processing models most relevant to laparoscopic surgery. Our review highlighted the necessity for a model that accounts for dynamic environments, perception, allocation of attention resources between the actions of both hands of an operator, and skill acquisition and retention. The results of the literature review were augmented through intraoperative observations of 7 colorectal surgical procedures, supported by laparoscopic video analysis of 12 colorectal procedures.

RESULTS

The Wickens human information-processing model was selected as the most relevant theoretical model to which we make adaptions for this specific application. We expanded the perception subsystem of the model to involve all aspects of perception during laparoscopic surgery. We extended the decision-making system to include dynamic decision-making to account for case/patient-specific and surgeon-specific deviations. The response subsystem now includes dual-task performance and nontechnical skills, such as intraoperative communication. The memory subsystem is expanded to include skill acquisition and retention.

CONCLUSIONS

Surgical decision-making during laparoscopic surgery is the result of a highly complex series of processes influenced not only by the operator's knowledge, but also patient anatomy and interaction with the surgical team. Newer developments in simulation-based education must focus on the theoretically supported elements and events that underpin skill acquisition and affect the cognitive abilities of novice surgeons. The proposed human information-processing model builds on established literature regarding information processing, accounting for a dynamic environment of laparoscopic surgery. This revised model may be used as a foundation for a model describing robotic surgery.

Memory Consolidation and Contextual Interference Effects with Computer Games

Some investigators of the contextual interference effect contend that there is a direct relation between the amount of practice and the contextual interference effect based on the prediction that the improvement in learning tasks in a random practice schedule, compared to a blocked practice schedule, increases in magnitude as the amount of practice during acquisition on the tasks increases. Research using computer games in contextual interference studies has yielded a large effect ( f = .50) with a random practice schedule advantage during transfer. These investigations had a total of 36 and 72 acquisition trials, respectively. The present study tested this prediction by having 72 college students, who were randomly assigned to a blocked or random practice schedule, practice 102 trials of three computer-game tasks across three days. After a 24-hr. interval, 6 retention and 5 transfer trials were performed. Dependent variables were time to complete an event in seconds and number of errors. No significant differences were found for retention and transfer. These results are discussed in terms of how the amount of practice, task-related factors, and memory consolidation mediate the contextual interference effect.

Contextual Interference: A Meta-Analytic Study

A meta-analysis of the contextual interference effect produced 139 estimates of effect sizes from 61 studies. The average overall effect size was .38. The effect size for basic research (.57) was significantly different from applied research (.19). Significant differences were also obtained between the effect sizes for adults (.50) and those for younger learners (.10). Power for retention and transfer scores was not significantly different. The overall mean power of the studies reviewed was .43.

Virtual Reality in Stroke Rehabilitation: A Systematic Review of its Effectiveness for Upper Limb Motor Recovery

PURPOSE

It is estimated that 50% to 75% of individuals who experience a stroke have persistent impairment of the affected upper limb (UL). There is a need to identify the best training strategies for retraining motor function of the UL. One intervention showing promise is virtual reality (VR), using either immersive or nonimmersive technology. Before recommending VR for use in clinical practice, it is important to understand the evidence regarding its effectiveness.

METHOD

Two questions about the effectiveness of VR for UL rehabilitation in stroke were posed: (1) Is the use of immersive VR more effective than conventional therapy or no therapy in the rehabilitation of the UL in patients with hemiplegia? (2) Is the use of nonimmersive VR more effective than conventional therapy or no therapy in the rehabilitation of the UL in patients with hemiplegia?

RESULTS

There is level 1b evidence suggesting an advantage to training in immersive VR environments versus no therapy in UL rehabilitation, and level 5 evidence for training in immersive VR versus conventional therapy. There is level 4 evidence showing conflicting results for training in nonimmersive VR versus no therapy, and level 2b evidence for training in nonimmersive VR versus conventional therapy.

CONCLUSION

The current evidence on the effectiveness of using VR in the rehabilitation of the UL in patients with stroke is limited but sufficiently encouraging to justify additional clinical trials in this population.

Learning of a golf putting task with varying contextual interference levels induced by feedback schedule in novices and experts

Switching between tasks during practice can affect motor learning. This study tested whether switching feedback content has any effects on learning to perform golf putts without full visibility. 60 participants (44 men, 16 women; M age = 26.3 yr., SD = 6.6) practiced golf putts without seeing the ball movement. 30 of the participants were golfers with moderate expertise, and 30 were novices. They received feedback regarding their putts, either on the angle or on the distance in one of three feedback schedules: blocked, serial-blocked, or serial. Independent of the expertise level, learning was not affected by the feedback schedule. The strong linkage between the two components--direction and distance--may have prevented a sufficient level of contextual interference.

Changes in performance over time while learning to use a myoelectric prosthesis

BACKGROUND

Training increases the functional use of an upper limb prosthesis, but little is known about how people learn to use their prosthesis. The aim of this study was to describe the changes in performance with an upper limb myoelectric prosthesis during practice. The results provide a basis to develop an evidence-based training program.

METHODS

Thirty-one able-bodied participants took part in an experiment as well as thirty-one age- and gender-matched controls. Participants in the experimental condition, randomly assigned to one of four groups, practiced with a myoelectric simulator for five sessions in a two-weeks period. Group 1 practiced direct grasping, Group 2 practiced indirect grasping, Group 3 practiced fixating, and Group 4 practiced a combination of all three tasks. The Southampton Hand Assessment Procedure (SHAP) was assessed in a pretest, posttest, and two retention tests. Participants in the control condition performed SHAP two times, two weeks apart with no practice in between. Compressible objects were used in the grasping tasks. Changes in end-point kinematics, joint angles, and grip force control, the latter measured by magnitude of object compression, were examined.

RESULTS

The experimental groups improved more on SHAP than the control group. Interestingly, the fixation group improved comparable to the other training groups on the SHAP. Improvement in global position of the prosthesis leveled off after three practice sessions, whereas learning to control grip force required more time. The indirect grasping group had the smallest object compression in the beginning and this did not change over time, whereas the direct grasping and the combination group had a decrease in compression over time. Moreover, the indirect grasping group had the smallest grasping time that did not vary over object rigidity, while for the other two groups the grasping time decreased with an increase in object rigidity.

CONCLUSIONS

A training program should spend more time on learning fine control aspects of the prosthetic hand during rehabilitation. Moreover, training should start with the indirect grasping task that has the best performance, which is probably due to the higher amount of useful information available from the sound hand.

Optimal training design for procedural motor skills: a review and application to laparoscopic surgery

This literature review covers the choices to consider in training complex procedural, perceptual and motor skills. In particular, we focus on laparoscopic surgery. An overview is provided of important training factors modulating the acquisition, durability, transfer, and efficiency of trained skills. We summarize empirical studies and their theoretical background on the topic of training complex cognitive and motor skills that are pertinent to proficiency in laparoscopic surgery. The overview pertains to surgical simulation training for laparoscopy, but also to training in other demanding procedural and dexterous tasks, such as aviation, managing complex systems and sports. Evidence-based recommendations are provided for facilitating efficiency in laparoscopic motor skill training such as session spacing, adaptive training, task variability, part-task training, mental imagery and deliberate practice.

Virtual reality versus conventional treatment of reaching ability in chronic stroke: clinical feasibility study

INTRODUCTION

The objective of this study was to evaluate the potential of exercises performed in a 2D video-capture virtual reality (VR) training environment to improve upper limb motor ability in stroke patients compared to those performed in conventional therapy.

METHODS

A small sample randomized control trial, in an outpatient rehabilitation center with 12 patients with chronic stroke, aged 33-80 years, who were randomly allocated to video-capture VR therapy and conventional therapy groups. All patients participated in four clinical evaluation sessions (pre-test 1, pre-test 2, post-test, follow-up) and nine 45-minute intervention sessions over a 3-week period. Main outcomes assessed were Body Structure and Function (impairment: Fugl-Meyer Assessment [FMA]; Composite Spasticity Index [CSI]; Reaching Performance Scale for Stroke), Activity (Box and Blocks; Wolf Motor Function Test [WMFT]), and Participation (Motor Activity Log) levels of the International Classification of Functioning.

RESULTS

Improvements occurred in both groups, but more patients in the VR group improved upper limb clinical impairment (FMA, CSI) and activity scores (WMFT) and improvements occurred earlier. Patients in the VR group also reported satisfaction with the novel treatment.

CONCLUSIONS

The modest advantage of VR over conventional training supports further investigation of the effect of video-capture VR or VR combined with conventional therapy in larger-scale randomized, more intense controlled studies.

Transfer Effects of Manipulating Temporal Constraints on Learning a Two-Choice Reaction Time Task with Low Stimulus-Response Compatibility

Recent research using deliberate amplification of spatial errors to increase motor learning leads to the question of whether amplifying temporal errors may also facilitate learning. We investigated transfer effects caused by manipulating temporal constraints on learning a two-choice reaction time (CRT) task with varying degrees of stimulus-response compatibility. Thirty-four participants were randomly assigned to one of the three groups and completed 120 trials during acquisition. For every fourth trial, one group was instructed to decrease CRT by 50 msec. relative to the previous trial and a second group was instructed to increase CRT by 50 msec. The third group (the control) was told not to change their responses. After a 5-min. break, participants completed a 40-trial no-feedback transfer test. A 40-trial delayed transfer test was administered 24 hours later. During acquisition, the Decreased Reaction Time group responded faster than the two other groups, but this group also made more errors than the other two groups. In the 5-min. delayed test (immediate transfer), the Decreased Reaction Time group had faster reaction times than the other two groups, while for the 24-hr. delayed test (delayed transfer), both the Decreased Reaction Time group and Increased Reaction Time group had significantly faster reaction times than the control. For delayed transfer, both Decreased and Increased Reaction Time groups reacted significantly faster than the control group. Analyses of error scores in the transfer tests indicated revealed no significant group differences. Results were discussed with regard to the notion of practice variability and goal-setting benefits.

Cognitive underpinnings of contextual interference during motor learning

The reported study examined the cognitive processes underlying contextual interference (CI) in motor learning. This experiment was designed to assess the combined influence of practice schedule (blocked or random) and task similarity (similar or dissimilar) on acquisition and retention performance. Participants (N=60) learned a set of three variations of a timing task according to a similar (900, 1000 and 1100ms) or dissimilar parameter condition (700, 1000 and 1300ms) with either a blocked or random practice order: this resulted in 4 experimental groups. Performance in delayed retention demonstrated a typical CI effect due to the schedule of practice for the dissimilar parameter condition with the random practice group outperforming the blocked practice group. Conversely, no blocked-random difference was found for the similar parameter condition. These findings lend support for the reconstruction hypothesis by showing that supplementing random practice with additional intertask elaboration (i.e., similar parameter condition) did not facilitate subsequent retention performance.

On the cognitive processes underlying contextual interference: Contributions of practice schedule, task similarity and amount of practice

This experiment was designed to assess the combined influence of practice schedule (blocked or random), task similarity (similar or dissimilar), and amount of practice on motor learning. Participants were required to perform three movement times (200, 350, and 500ms) in a blocked or random schedule while pointing towards the target located in the front direction in the similar condition, or towards three targets (left, front, and right) in the dissimilar condition. In each condition, participants completed 99 or 297 acquisition trials before a delayed retention test similar for all participants. Results indicated a contextual interference (CI) effect due to the schedule of practice following 297 trials for similar task variations: blocked schedule tended to produce better performance early in practice; random schedule enhanced learning for a larger amount of practice. However, when participants experienced dissimilar task variations, no blocked-random difference was found whatever the amount of practice. This suggests that task similarity is a learning variable that modulates the CI effect. Our findings argue for the evidence that the intertask processing evoked by random schedule is not sufficient to improve learning and that there may be a ceiling effect on retention performance due to the extent of additional intertask processing.

Critical features of training that facilitate adaptive generalization of over ground locomotion

When subjects learn motor tasks under novel visuomotor conditions variations in sensory input during training facilitate adaptive generalization. We tested the hypotheses that training with multiple sensory input variations is more effective than a single or no variation and that training must include critical features of the criterion task. Normal adults were pre- and post-tested on an obstacle avoidance task while wearing visual distortion lenses after treadmill walking (Experiment 1), or balance training (Experiment 2). Subjects were randomized to training groups in which they wore either: (1) three different visual distortion lenses, (2) a single pair of visual distortion lenses, or (3) sham lenses. Post-tests were done while wearing novel lenses. In Experiment 1 subjects who trained with multiple lenses adapted better than single or sham lens groups. The single lens-training group with magnifying lenses adapted better than the other single lens groups. In Experiment 2, training for dynamic balance, alone, did not increase training efficacy. Thus, training for an obstacle avoidance task in a novel visual environment required a critical feature of the criterion task: locomotion. Constant practice with a single lens was successful only if the best lens was selected, but the best lens could not be known ahead of time. Therefore variable practice with multiple lenses on a task that included a critical feature of the criterion task was the best training strategy to enhance adaptive generalization.

The role of order of practice in learning to handle an upper-limb prosthesis

OBJECTIVE

To determine which order of presentation of practice tasks had the highest effect on using an upper-limb prosthetic simulator.

DESIGN

A cohort analytic study.

SETTING

University laboratory.

PARTICIPANTS

Healthy, able-bodied participants (N=72) randomly assigned to 1 of 8 groups, each composed of 9 men and 9 women.

INTERVENTIONS

Participants (n=36) used a myoelectric simulator, and participants (n=36) used a body-powered simulator. On day 1, participants performed 3 tasks in the acquisition phase. On day 2, participants performed a retention test and a transfer test. For each simulator, there were 4 groups of participants: group 1 practiced random and was tested random, group 2 practiced random and was tested blocked, group 3 practiced blocked and was tested random, and group 4 practiced blocked and was tested blocked.

MAIN OUTCOME MEASURES

Initiation time, the time from the starting signal until the beginning of the movement, and movement time, the time from the beginning until the end of the movement.

RESULTS

Movement times got faster during acquisition (P<.001). The blocked group had faster movement times (P=.009), and learning in this group extended over the complete acquisition phase (P<.001). However, this advantage disappeared in the retention and transfer tests. Compared with a myoelectric simulator, movements with the body-powered simulator were faster in acquisition (P=.004) and transfer test (P=.034).

CONCLUSIONS

Performance in daily life with a prosthesis is indifferent to the structure in which the training is set up. However, practicing in a blocked fashion leads to faster performance; in novice trainees, it might be suggested to practice part of the training tasks in blocks.

Impact of exercise on seniors' motor control response to external dynamics

Research on postural stability, motor control, and fall occurrence in seniors is common, but few studies address the influence of exercise and external dynamics on elderly balance. Using pre- and post-training tests, the effects of a Fitball exercise program on performance in eight subjects was documented. The exercise program focused on improving dynamic balance and postural stability of seniors. To evaluate progress-related changes, pre- and post-tests in a dynamic environment were applied. Center of gravity (COG) excursion, catch success rate, and balance success rate were quantified, and synchronized data collection of 3D motion capture (VICON v8i) and ground reaction force (2 KISTLER platforms) was analyzed. During pre- and post-tests, participants stood in a walklike stance and were asked to catch a weighted ball, which dropped unexpectedly. Results showed no significant changes in balance success rate. Significant improvements were found, however, in both COG control and catch success rate following training (p<0.05).

Biodynamic Feedback Training to Assure Learning Partial Load Bearing on Forearm Crutches

OBJECTIVE

To examine how biodynamic feedback training affects the learning of prescribed partial load bearing (200N).

DESIGN

Three pre-post experiments.

SETTING

Biomechanics laboratory in a German university.

PARTICIPANTS

A volunteer sample of 98 uninjured subjects who had not used crutches recently. There were 24 subjects in experiment 1 (mean age, 23.2y); 64 in experiment 2 (mean age, 43.6y); and 10 in experiment 3 (mean age, 40.3y), parallelized by arm force.

INTERVENTIONS

Video instruction and feedback training: In experiment 1, 2 varied instruction videos and reduced feedback frequency; in experiment 2, varied frequencies of changing tasks (contextual interference); and in experiment 3, feedback training (walking) and transfer (stair tasks).

MAIN OUTCOME MEASURE

Vertical ground reaction force.

RESULTS

Absolute error of practiced tasks was significantly reduced for all samples (P<.050). Varied contextual interference conditions did not significantly affect retention (P=.798) or transfer (P=.897). Positive transfer between tasks was significant in experiment 2 (P<.001) and was contrary to findings in experiment 3 (P=.071).

CONCLUSIONS

Biodynamic feedback training is applicable for learning prescribed partial load bearing. The frequency of changing tasks is irrelevant. Despite some support for transfer effects, additional practice in climbing and descending stairs might be beneficial.

Intermittent practice facilitates stable motor memories

Humans adaptively control reaching movements to maintain good performance in the presence of novel forces acting on the arm. A recent study suggested that motor memories of different force conditions are not transformed from fragile to stable states, but rather are always vulnerable to interference from newly learned conditions (Caithness et al., 2004). This is contrary to the results of previous studies (Brashers-Krug et al., 1996; Shadmehr and Brashers-Krug, 1997), although all of these studies followed similar methods. Here, we show that a seemingly insignificant and inconsistently applied methodological detail may reconcile this discrepancy. Catch trials, in which the novel forces are removed, may be randomly interspersed among the more frequent force trials to assess how a subject is learning to predict the pattern of forces. In the absence of an interfering condition, subjects retained their learning until retest a day later regardless of whether they experienced catch trials. But in the presence of an interfering condition, only the subjects who had experienced forces intermittently retained their learning and thereby showed resistance to the interference. Thus, intermittent rather than constant practice conditions appear to be critical for dynamic motor memory stabilization.

Obstacle avoidance in novel visual environments improved by variable practice training

Motor performance on simple tasks improves after training in variable practice. We asked if locomotor skill during an obstacle-avoidance task in a novel sensorimotor environment improved through training in variable practice on other complex tasks. 40 normal adults practiced gross motor skills while wearing either sham lenses, one of several visual distortion lens (constant practice), or three different visual distortion lenses (variable practice). Posttests on obstacle avoidance with novel lenses showed significantly better scores with variable practice and one of the constant groups vs sham lenses. Constant and variable practice groups did not differ. Thus, performance in a novel environment improves after training on similar type novelty, even when practice and test conditions differ. Constant practice was effective only if the subjects used the lens efficacious in training. Variable practice increases the likelihood of efficacious training when adaptive performance is required in a novel environment.

Differential transfer benefits of increased practice for constant, blocked, and serial practice schedules

The effects of practice schedule and amount of practice on the development of the generalized motor program (GMP) and on parameter estimation were investigated. Participants (N = 108) practiced the same relative timing but different absolute durations of a multisegment timing task. Practice schedules (constant, blocked, or serial) were crossed with amounts of practice (low and high). Inclusion of a constant practice condition allowed the authors to investigate the variability of practice prediction. Participants practiced the same proportional durations in a serial or a blocked schedule, which enabled the authors to examine contextual interference. A constant practice schedule enhanced GMP performance when task parameters remained the same, but varied practice schedules were beneficial when task parameters changed. A serial as opposed to a blocked practice schedule was superior when the performance of a task governed by a different GMP was required. Increased practice led to a consolidated task representation that was unavailable for updating.

Variability effects on retention of a motor skill in elementary school children

Variability effects on learning, retention, and transfer of motor skills have been a main issue for scientists involved in laboratory and field research. Variable practice is intended as parameter variations of a generalized motor program as well as rehearsal of different motor programs. Although the benefits deriving from variable practice on motor skill retention appear quite robust in laboratory settings, field investigations have produced mixed results. Hence, the aim of this study was to examine the effects of different variable schedules on the retention of a complex min tor skill in a physical education setting. 61 elementary school children were assigned Blocked/Nonvariable, Blocked/Variable, Serial/Nonvariable, or Serial/Variable schedules, and practiced two tasks (throwing and hurdle running) and a complex skill (jumping) across 14 lessons. Improved performance in the complex skill was found after practice, with the Serial/Nonvariable group outperforming all other groups. Therefore. the rehearsal of different motor programs was beneficial for jumping skill retention, whereas parameter variation was not.

Examining the effect of practice on inhibition of return in static displays

In a recent article, Weaver, Lupiáñez, and Watson (1998) reported that both object-based and location-based inhibition of return effects were reduced with practice. The present study was conducted to (1) replicate the reduction of inhibition of return with practice in single-session experiments with a variety of displays and responses and (2) to examine the notion that the reduction was, at least partly, due to habituation. However, no evidence for practice-related changes in the size of the inhibitory effect were found over a series of different inhibition of return experiments using static displays (using various numbers of target locations, types of keypress responses, and number of trials). Overall, the results suggest that inhibition of return is a robust phenomenon and may not, with static displays, be especially sensitive to practice effects.

The contextual interference effect in parameter modifications of the same generalized motor program

This study extended previous work (Sekiya, Magill, Sidaway, & Anderson, 1994) by examining whether the contextual interference (CI) effect could be found when task variations were controlled by the same generalized motor program (GMP) but differentiated on the basis of overall force parameter modifications. A subsidiary aim of this study was to determine how the amount of practice influenced the CI effect. During 2 acquisition sessions and 2 retention sessions, participants (N = 24) performed 3 task variations in either a blocked (low CI) or serial (high CI) condition. The task variations shared the same relative force structures but differed in the amount of overall force that had to be produced. Analysis of a general error measure revealed a strong CI effect, indicating that overall force parameter modifications of the same GMP created the CI effect. Analyses of various dependent measures, which dissociated GMP from parameter components with regard to force characteristics, revealed that parameter learning, but not GMP learning, was enhanced by high CI practice. No CI effect occurred in any aspect of timing characteristics. The amount of practice used in the present study did not influence the efficacy of the CI effect.