Development of Multiple Movement Representations With Practice: Specificity Versus Flexibility

The question addressed in the present experiment was whether an individual who practices a task under different conditions of afferent information develops different movement representations, each of which is based on the most accurate source of afferent information for movement control. In Experiment 1, participants (N = 23) performed a manual aiming movement in a target-only condition for 520 trials before performing in a normal vision condition for an equivalent amount of practice. Control groups performed all practice trials in either a normal vision or a target-only condition. The results revealed that the movement representation developed in the initial (target-only) practice phase remained accessible for movement planning and control. The results of Experiment 2 indicated, however, that participants did not maintain such a representation when their initial practice in the target-only condition was reduced (40 or 160 trials) before they had extensive practice in normal vision. Those results indicate that extensive practice in a target-only and then in a normal vision condition enables an individual to plan and control his or her movement on the basis of the most efficient source of available afferent information. Because visual afferent information provides optimal information for ensuring movement accuracy, however, if initial practice in the target-only condition is only modest or moderate it is likely that that information source will progressively dominate all other sources of afferent information for movement planning and control.     

Development of multiple movement representations with practice: specificity versus flexibility

The question addressed in the present experiment was whether an individual who practices a task under different conditions of afferent information develops different movement representations, each of which is based on the most accurate source of afferent information for movement control. In Experiment 1, participants (N = 23) performed a manual aiming movement in a target-only condition for 520 trials before performing in a normal vision condition for an equivalent amount of practice. Control groups performed all practice trials in either a normal vision or a target-only condition. The results revealed that the movement representation developed in the initial (target-only) practice phase remained accessible for movement planning and control. The results of Experiment 2 indicated, however, that participants did not maintain such a representation when their initial practice in the target-only condition was reduced (40 or 160 trials) before they had extensive practice in normal vision. Those results indicate that extensive practice in a target-only and then in a normal vision condition enables an individual to plan and control his or her movement on the basis of the most efficient source of available afferent information. Because visual afferent information provides optimal information for ensuring movement accuracy, however, if initial practice in the target-only condition is only modest or moderate it is likely that that information source will progressively dominate all other sources of afferent information for movement planning and control.     

The effect of practice on component submovements is dependent on the availability of visual feedback

Participants (N = 16) were given extensive practice (1,500 trials) on a perceptual-motor aiming task. The full-vision (FV) group practiced with vision of their response cursor, whereas the no-vision (NV) group practiced in a condition without vision. Movements were made as quickly and accurately as possible, and knowledge of results (KR) was provided. The authors tested the importance of vision early and late in practice by transferring participants to the NV condition without KR. The effects of practice differed between the two conditions. The FV group increased the speed of initial impulse to get to the target quickly, then relied on vision to make discrete error corrections. Transfer tests revealed that reliance on vision remained after extensive practice. For the NV group, practice effects were associated with a reduction in the extent to which discrete error corrections were produced.     

Specificity of practice: interaction between concurrent sensory information and terminal feedback

In 2 experiments, the authors investigated a potential interaction involving the processing of concurrent feedback using design features from the specificity of practice literature and the processing of terminal feedback using a manipulation from the guidance hypothesis literature. In Experiment 1, participants produced (198 trials) flexion-extension movements to reproduce a specific pattern of displacement over time with or without vision of the limb position and with 100% or 33% knowledge of results (KR) frequency. The transfer test was performed without vision and KR. In Experiment 2, the authors assessed whether sensory information processing was modulated by the amount of practice. Participants performed 54 or 396 trials under a 100% or a 33% KR frequency with vision before being transferred to a no-vision condition without KR. Results of both experiments indicated that the Vision-33% condition suffered a larger detrimental effect of withdrawing visual information than the Vision-100% condition. Experiment 2 indicated that this detrimental effect increased with practice. These results indicated the reduction in terminal feedback prompted participants to more deeply process the concurrent visual information thus reinforcing their dependency on the visual information.     

The Effect of Practice on Component Submovements is Dependent on the Availability of Visual Feedback

Participants (N = 16) were given extensive practice (1,500 trials) on a perceptual-motor aiming task. The full-vision (FV) group practiced with vision of their response cursor, whereas the no vision (NV) group practiced in a condition without vision. Movements were made as quickly and accurately as possible, and knowledge of results (KR) was provided. The authors tested the importance of vision early and late in practice by transferring participants to the NV condition without KR. The effects of practice differed between the two conditions. The FV group increased the speed of initial impulse to get to the target quickly, then relied on vision so make discrete error corrections. Transfer tests revealed that reliance on vision remained after extensive practice. For the NV group, practice effects were associated with a reduction in the extent to which discrete error corrections were produced.     

Specificity of practice in a ball interception task.

Learning of an aiming task has been shown to be specific to the sources of afferent information available during practice. However, this has not been the case when a one-hand ball-catching task has been used. The goal of the present study was to determine the cause of these conflicting results. Participants practiced an interception task in either a normal vision condition or a ball-only condition. They were all then transferred to the ball-only condition, using either the same ball trajectories as in acquisition or different ones. Being transferred from a normal vision condition to a ball-only condition resulted in a significant increase in spatial interception errors, thus supporting the specificity of practice hypothesis. Using new ball trajectories in transfer caused a significant increase in error for all participants. The pattern of errors observed when new ball trajectories were used suggests that participants had difficulty correlating information about the location of their arm via proprioception and a combination of retinal and extra-retinal information about the ball trajectory.     

The Effect of Practice on the Control of Rapid Aiming Movements: Evidence for an Interdependency Between Programming and Feedback Processing

The purpose of this experiment was to investigate how the control of aiming movements performed as fast and as accurately as possible changes with practice. We examined: (1) the influence of visual feedback on the initial impulse and error correction phases of aiming movements during acquisition; and (2) the effect of removing visual feedback at different levels of practice. Results from the acquisition trials indicated that vision had a major impact on the organization of the initial impulse and error correction phases. Also, consistent with findings from research involving temporally constrained movements, the cost of removing vision was greater after extensive levels than after moderate levels of practice. Collectively, these results denote the importance of visual feedback to the learning of this particular class of aiming movements. Learning appears to be a dual process of improved programming of the initial impulse and increased efficiency of feedback processing. Practice not only acts on programming and feedback processes directly, but also indirectly through a reciprocal interplay between these two processes.     

Hand preference, practice order, and spatial assimilations in rapid bimanual movement

When subjects make rapid bimanual aiming movements over different distances, spatial assimilations are shown; the shorter distance limb overshoots when paired with a longer distance limb. Recent research has also shown spatial assimilations to be greater in the nonpreferred left limb of right-handed subjects, but it is not known whether the increased spatial assimilations represent a handedness effect or one of hemispheric lateralization of motor control. To determine the nature of the asymmetric effect, left- (n = 32) and right- (n = 60) handed subjects part practiced, then whole practiced, short (20 degrees ) and long 60 degrees ) reversal movements. During whole practice, both groups showed spatial assimilations in the shorter distance limb, particularly when the left limb performed the short movement. This asymmetry was greatest for right-handed subjects, but left-handed subjects showed smaller, but systematic effects, providing moderate support for the hypothesis that the asymmetric effect is due to hemispheric lateralization of motor control. All interlimb differences in spatial accuracy for the short and long movements were eliminated with practice, however, suggesting the asymmetric effect was temporary as well. In addition, subjects who part practiced the long movement just prior to whole practice showed greater overshooting in the short distance limb compared with subjects who followed the other practice order throughout whole practice and the no-KR retention trials. Such findings suggest that the part-practice order of bimanual tasks can directionally bias whole-task performance.     

Is there "feedback" during visual imagery? Evidence from a specificity of practice paradigm.

The specificity of practice hypothesis predicts the development of a sensorimotor representation specific to the afferent feedback available during skill acquisition (Proteau, 1992; Proteau, Marteniuk, Girouard, & Dugas, 1987). In the present investigation, we used the specificity of practice hypothesis to test whether skill acquisition through visual imagery would lead to the development of a sensory-specific movement representation similar to one resulting from actual practice. To accomplish this objective, participants practiced walking a 12-m linear path in one of three practice conditions, full-vision (FV), no-vision (NV), or visual imagery (VI), for either 10 or 100 trials. Knowledge of spatial and/or temporal results (KR) was provided to participants following each trial during this phase. Following acquisition, participants completed 10 NV trials without KR. An analysis of root-mean-squared-error (RMSE) indicated NV participants were more accurate than both FV and VI participants in the transfer condition. We believe the equivalence in transfer RMSE between FV and VI suggests that there are similarities between the movement representations attained by FV and VI practice.     

Online versus offline processing of visual feedback in the production of component submovements

The present authors tested the assumptions in R. S. Woodworth's (1899) 2-component model regarding the specific roles of vision in the production of both the initial impulse and the error-correction phases of movement. Participants (N = 40) practiced a rapid aiming task (1,500 trials), with either no visual feedback, vision of only the 1st 50% of the movement, vision of only the 1st 75% of the movement, or vision of the entire movement. Consistent with previous research, the availability of vision over the 1st half of the movement had no effect on aiming accuracy during acquisition. In contrast, when visual feedback was available over the 1st 75% of the movement and the entire movement, initial impulse endpoints were less variable and the efficiency of the error-correction phase was improved. Analysis of spatial variability at various stages in the movement revealed that participants processed visual feedback offline to improve programming of the initial impulse and processed it online in regulating the deceleration of the initial impulse.     

Effects of Visual Information and Task Constraints on Intersegmental Coordination in Playground Swinging

The authors investigated how and to what extent visual information and associated task constraints are negotiated in the coordinative structure of playground swinging. Participants (N = 20) were invited to pump a swing from rest to a prescribed maximal amplitude under 4 conditions: normal vision, no vision, and 2 visual conditions involving explicit phasing constraints. In the latter conditions, participants were presented with a flow pattern consisting of a periodically expanding and contracting optical structure. They were instructed to phase the swing motion so that the forward turning point coincided with either the maximal size (enhanced optical flow) or the minimal size (reduced optical flow) of the presented flow pattern. Removal of visual information clearly influenced the swinging behavior, in that intersegmental coordination became more stereotyped, reflecting a general stiffening of the swinger. The conditions involving explicit phasing requirements also affected the coordination, but in an opposite way: The coordination became less stereotyped. The two phasing instructions had differential effects: The intersegmental coordination deviated more from normal swinging (i.e., without phasing constraints) when optical flow was enhanced than when it was reduced. Collectively, those findings show that visual information plays a formative role in the coordinative structure of swinging, in that variations of visual information and task constraints were accompanied by subtle yet noticeable changes in intersegmental coordination.     

Online Versus Offline Processing of Visual Feedback in the Production of Component Submovements

The present authors tested the assumptions in R. S. Woodworth's (1899) 2-component model regarding the specific roles of vision in the production of both the initial impulse and the error-correction phases of movement. Participants (N = 40) practiced a rapid aiming task (1,500 trials), with either no visual feedback, vision of only the 1st 50% of the movement, vision of only the 1st 75% of the movement, or vision of the entire movement. Consistent with previous research, the availability of vision over the 1st half of the movement had no effect on aiming accuracy during acquisition. In contrast, when visual feedback was available over the 1st 75% of the movement and the entire movement, initial impulse endpoints were less variable and the efficiency of the error-correction phase was improved. Analysis of spatial variability at various stages in the movement revealed that participants processed visual feedback offline to improve programming of the initial impulse and processed it online in regulating the deceleration of the initial impulse.     

Movement substructures change as a function of practice in children and adults

An experiment is reported in which participants at 6 (n = 20), 9 (n = 20), and 24 years (n = 20) of age either received or did not receive practice on a rapid aiming task using the arm and hand. The purpose of the experiment was to document the changes in movement substructures (in addition to movement time) as a function of practice. After receiving 10 baseline trials, subjects in the practice groups received 30 practice trials followed by 10 retention trials on each of 5 days, while subjects in the no-practice group had only baseline and retention trials. Retention-only trials were divided into primary (reflecting the ballistic controlled part of the movement) and secondary (reflecting corrective movement adjustments) submovements. In addition, jerk (the 3rd derivative of movement displacement) was calculated as an estimate of the smoothness of the movement. Participants increased the primary submovement as a function of practice; however, the increases were substantially larger in the children (25-30%) than in the adults (10%). Participants also decreased jerk as a function of practice and the decreases were greater in children than in adults. The results suggest that with practice the primary submovement is lengthened so that it ends nearer the target, especially in children. Associated with the primary submovement covering a larger percentage of the movement length and time, movements became smoother.     

Optimizing the Use of Vision in Manual Aiming: The Role of Practice

The purpose of this study was to determine how subjects learn to adjust the characteristics of their manual aiming movements in order to make optimal use of the visual information and reduce movement error. Subjects practised aiming (120 trials) with visual information available for either 400 msec or 600 msec. Following acquisition, they were transferred to conditions in which visual information was available for either more or less time. Over acquisition, subjects appeared to reduce target-aiming error by moving to the target area more quickly in order to make greater use of vision when in the vicinity of the target. With practice, there was also a reduction in the number of modifications in the movement. After transfer, both performance and kinematic data indicated that the time for which visual information was available was a more important predictor of aiming error than the similarity between training and transfer conditions. These findings are not consistent with a strong “specificity of learning” position. They also suggest that, if some sort of general representation or motor programme develops with practice, that representation includes rules or procedures for the utilization of visual feedback to allow for the on-line adjustment of the goal-directed movement.     

Afferent Information for Motor Control: The Role of Visual Information in Different Portions of the Movement

The question addressed in the present study was whether subjects (N = 24) can use visual information about their hand, in the first half of an aiming movement, to ensure optimal directional accuracy of their aiming movements. Four groups of subjects practiced an aiming task in either a complete vision condition, a no-vision condition, or in a condition in which their hand was visible for the first half [initial vision condition (IV)] or the second half of the movement [final vision condition (FV)]. Following 240 trials of acquisition, all subjects were submitted to a transfer test that consisted of 40 trials performed in a no-vision condition. The results indicated that seeing the hand early in movement did not help subjects to optimize either directional or amplitude accuracy. On the other hand, when subjects viewed their hand closer to the target, movements resulted that were as accurate as those performed under a complete vision condition. In transfer, withdrawing vision did not cause any increase in aiming error for the IV or the no-vision conditions. These results replicated those of Carlton (1981) and extended those of Bard and colleagues (Bard, Hay, & Fleury, 1985) in that they indicated that the kinetic visual channel hypothesized by Paillard (1980; Paillard & Amblard, 1985) appeared to be inoperative beyond 40deg of visual angle.     

Effects of visual information and task constraints on intersegmental coordination in playground swinging

The authors investigated how and to what extent visual information and associated task constraints are negotiated in the coordinative structure of playground swinging. Participants (N = 20) were invited to pump a swing from rest to a prescribed maximal amplitude under 4 conditions: normal vision, no vision, and 2 visual conditions involving explicit phasing constraints. In the latter conditions, participants were presented with a flow pattern consisting of a periodically expanding and contracting optical structure. They were instructed to phase the swing motion so that the forward turning point coincided with either the maximal size (enhanced optical flow) or the minimal size (reduced optical flow) of the presented flow pattern. Removal of visual information clearly influenced the swinging behavior, in that intersegmental coordination became more stereotyped, reflecting a general stiffening of the swinger. The conditions involving explicit phasing requirements also affected the coordination, but in an opposite way: The coordination became less stereotyped. The two phasing instructions had differential effects: The intersegmental coordination deviated more from normal swinging (i.e., without phasing constraints) when optical flow was enhanced than when it was reduced. Collectively, those findings show that visual information plays a formative role in the coordinative structure of swinging, in that variations of visual information and task constraints were accompanied by subtle yet noticeable changes in intersegmental coordination.     

Transfer as a function of exploration and stabilization in original practice

The identification of practice conditions that provide flexibility to perform successfully in transfer is a long-standing issue in motor learning but is still not well understood. Here we investigated the hypothesis that a search strategy that encompasses both exploration and stabilization of the perceptual-motor workspace will enhance performance in transfer. Twenty-two participants practiced a virtual projection task (120 trials on each of 3 days) and subsequently performed two transfer conditions (20 trials/condition) with different constraints in the angle to project the object. The findings revealed a quadratic relation between exploration in practice (indexed by autocorrelation and distribution of error) and subsequent performance error in transfer. The integration of exploration and stabilization of the perceptual-motor workspace enhances transfer to tasks with different constraints on the scaling of motor output.     

Separate movement planning and spatial assimilation effects in sequential bimanual aiming movements

This study extended earlier work by showing spatial assimilations in sequential bimanual aiming movements when the participant preplanned only the first movement of a two-movement sequence. Right-handed participants (n=20, aged 18 to 22 years) made rapid lever reversals of 20 degrees and 60 degrees singly and sequentially with an intermovement interval of 2.5 sec. Following blocked single practice of both movements in each hand (15 trials each), two sets of 30 sequential practice trials were completed. The sequences began with either the long or the short movement and the participant always knew the goal of the first movement. During the intermovement interval, the experimenter gave instructions to complete the sequence with a short movement, a long movement, or no movement in a random order. Compared to the single trials, both movements in the sequence overshot the short-distance and undershot the long-distance goal. Spatial errors increased when a change in the movement goal was required for the second movement in the sequence. The experiment demonstrated that separate planning of sequential aiming movements can reduce spatial assimilation effects, but interference due to practice organization and switching the task's goal must also be overcome in order to produce accurate aiming movements.     

Self-controlled practice: Autonomy protects perceptions of competence and enhances motor learning

ObjectiveIn previous self-controlled feedback studies, it was observed that participants who could control their own feedback schedules usually use a strategy of choosing feedback after successful trials, and present superior motor learning when compared with participants who were not allowed to choose. Yoked participants of these studies, however, were thwarted not only regarding autonomy but also, presumably, regarding perceived competence, as their feedback schedules were provided randomly, regarding good or bad trials. The purpose of the present study was to examine whether self-controlled feedback schedules would have differential effects on learning if yoked participants are provided with feedback after good trials at the same rate as their self-controlled counterparts.DesignExperimental study with two groups. Timing accuracy was assessed in two different experimental phases, supplemented by questionnaire data.MethodParticipants practiced a coincident-anticipation timing task with a self-controlled or yoked feedback schedule during practice. Participants of the self-controlled group were able to ask for feedback for two trials, after each of five 6-trial practice blocks. Yoked participants received a feedback schedule matching the self-control group schedule, according to accuracy.ResultsParticipants asked for (self-controlled group) and received (yoked group) feedback, mainly after relatively good trials. However, participants of the self-controlled group reported greater self-efficacy at the end of practice, and performed with greater accuracy one day later, on the retention test, than the yoked group.ConclusionsThe findings indicate that the autonomy provided by self-controlled feedback protocols can raise learners' perceptions of competence, with positive consequences on motor learning.     

Autonomy support and preference-performance dissociation in choice-reaction time tasks

The purpose of the current study was threefold: (a) to examine the effects of participants having the autonomy to choose the practice order of two reaction time (RT) tasks – a choice-RT task and a Simon task – on performance, (b) to examine whether one order of practice is better than the other, and (c) to examine whether participants might choose a practice order that hinders their performance. The study was conducted online and participants completed the tasks on their own computer. Fifty-nine participants were randomly assigned into three groups: (a) autonomy – participants chose which task they would like to practice first, (b) choice-first – participants practiced the choice-RT task first, and (c) Simon-first – participants practiced the Simon task first. Out of these three groups we created an autonomy group (n = 17) and a no-autonomy (yoked) group (n = 17). All participants performed eight familiarization trials of each task, practiced 160 trials (8 blocks × 20 trials) of each task, and performed a post-test of 20 additional trials of each task after a three-minute rest. The main findings were that (a) participants in the autonomy group had faster RTs compared with participants in the no-autonomy group, (b) performing the choice-RT task first led to faster RTs compared with performing the Simon task first, and (c) nine of the 17 participants in the autonomy group chose to practice the Simon task first. The findings of this study suggest that providing participants with autonomy can lead to improved performance. However, there may be a dissociation between participants' preference of practice order and their performance.