Determinants of offline processing of visual information for the control of reaching movements

The authors investigated the use of visual feedback as a form of knowledge of results (KR) for the control of rapid (200-250 ms) reaching movements in 40 participants. They compared endpoint accuracy and intraindividual variability of a full-vision group (FV) with those of no-vision groups provided with KR regarding (a) the endpoint in numerical form, (b) the endpoint in visual form, or (c) the endpoint and the trajectory in visual form (DEL). The FV group was more accurate and less variable than were the no-vision groups, and the analysis of limb trajectory variability indicated that their superior performance resulted primarily from better movement planning rather than from online visual processes. The FV group outperformed the DEL group even though both groups were obtaining the same amount of spatial visual information from every movement. That finding suggests that the effectiveness with which visual feedback is processed offline is not a simple function of the amount of visual information available, but depends on how that information is presented.     

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 control of movement amplitude

Researchers have suggested that visual feedback not only plays a role in the correction of errors during movement execution but that visual feedback from a completed movement is processed offline to improve programming on upcoming trials. In the present study, we examined the potential contribution of online and offline processing of visual feedback by analysing spatial variability at various kinematic landmarks in the limb trajectory (peak acceleration, peak velocity, peak negative acceleration and movement end). Participants performed a single degree of freedom video aiming task with and without vision of the cursor under four criterion movement times (225, 300, 375 and 450 ms). For movement times of 225 and 300 ms, the full vision condition was less variable than the no vision condition. However, the form of the variability profiles did not differ between visual conditions suggesting that the contribution of visual feedback was due to offline processes. In the 375 and 450 ms conditions, there was evidence for both online and offline control as the form of the variability profiles differed significantly between visual conditions.     

Effect of bandwidth knowledge of results on movement consistency

The effect of "bandwidth" knowledge of results (KR), given only if the subject's response is outside of a certain movement-time bandwidth, on learning and performance of a rapid elbow-flexion movement was examined. Subjects were randomly assigned to one of three feedback groups, a 5% bandwidth group (BW5), a 10% bandwidth group (BW10), or a control group (KR), who received knowledge of results on every trial. Subjects moved a light, horizontal, aluminum lever through 60 degrees in 200 msec., for 100 acquisition trials with KR given depending on group and 25 transfer trials without KR (transfer phase). Although the subjects in the BW10 group received knowledge of results fewer times during acquisition, they showed less within-subject variability than the BW5 and KR groups on the transfer test which suggests that giving KR about a relatively large bandwidth enhances movement consistency.     

Movement trajectory smoothness is not associated with the endpoint accuracy of rapid multi-joint arm movements in young and older adults

The minimum variance theory proposes that motor commands are corrupted by signal-dependent noise and smooth trajectories with low noise levels are selected to minimize endpoint error and endpoint variability. The purpose of the study was to determine the contribution of trajectory smoothness to the endpoint accuracy and endpoint variability of rapid multi-joint arm movements. Young and older adults performed arm movements (4 blocks of 25 trials) as fast and as accurately as possible to a target with the right (dominant) arm. Endpoint accuracy and endpoint variability along with trajectory smoothness and error were quantified for each block of trials. Endpoint error and endpoint variance were greater in older adults compared with young adults, but decreased at a similar rate with practice for the two age groups. The greater endpoint error and endpoint variance exhibited by older adults were primarily due to impairments in movement extent control and not movement direction control. The normalized jerk was similar for the two age groups, but was not strongly associated with endpoint error or endpoint variance for either group. However, endpoint variance was strongly associated with endpoint error for both the young and older adults. Finally, trajectory error was similar for both groups and was weakly associated with endpoint error for the older adults. The findings are not consistent with the predictions of the minimum variance theory, but support and extend previous observations that movement trajectories and endpoints are planned independently.     

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.     

Average KR schedule in learning of timing: influence of length for summary knowledge of results and task complexity

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

The independence of recall and recognition in motor learning

A basic tenet of both current closed-loop theories of motor learning (Adams, 1971; Schmidt, 1975) is that the generation of response specifications during learning is required for the development of recall memory. Two experiments were performed to test this tenet by attempting to demonstrate the development of recall memory in the absence of response specification production. The task in both experiments required blindfolded subjects to learn to produce a rapid, novel criterion movement on a linear positioning device. Control subjects in both experiments actively produced movements during learning with knowledge of results (KR) while experimental subjects in Experiment 1 experienced only the endpoint locations and in Experiment 2 were passively moved to the endpoint locations. Following initial KR trials, both experimental and control groups attempted to actively produce the criterion movement in the absence of KR. The results of both experiments support closed-loop theory that active practice is required to develop recall memory. There was some suggestion, however, that passive experience with sensory feedback may also aid recall memory development, contrary to the two closed-loop theories.     

Effects of normative feedback on motor learning are dependent on the frequency of knowledge of results

Studies on normative feedback have shown superior motor learning outcomes for individuals who believe that they are performing better than others through increased self-efficacy. Nevertheless, the effects of normative feedback were never dissociated from the knowledge of results (KR) provided to the learners which potentially interacts with self-efficacy as well. Thus, we investigated whether the effects of normative feedback on motor learning, associated with self-efficacy, would be dependent on the amount of KR provided. Fifty-six participants were randomly assigned to four experimental groups in terms of KR frequency (100% and 33%) and normative feedback (positive and negative). In the acquisition phase, all groups received the average KR of their performance at the end of each block of trials (True feedback) and a fake KR based on their own performance (but said to be from a group of participants who practiced the same task) (False Feedback). The False Feedback indicated better or worse performance of the participant in comparison to the fake group, depending on their experimental group. Retention tests were performed immediately and after 24 h from the acquisition phase. To measure self-efficacy, a questionnaire on participant's efficacy was applied before the first block, after each block of trials and before the retention tests. The results revealed superiority of positive normative feedback and 100% KR frequency, compared to negative normative feedback and 100% KR frequency in the 24h retention test. No difference was found between the groups with a frequency of 33% of KR (positive and negative). All groups increased self-efficacy during practice, but there was no difference between groups at any stage of the study. We conclude that the effects of normative feedback on motor learning are dependent on the KR frequency. However, they were not associated with self-efficacy.     

The Learning of Programmed- and Feedback-Based Processes Controlling the Production of a Positioning Response in Two Dimensions

Two experiments were conducted to investigate the learning of the programmed- and feedback-based processes controlling the production of a slow, self-paced positioning response in two dimensions (direction and extent) in the horizontal plane. Both experiments had two phases: an acquisition phase of 60 trials with KR, followed by a KR withdrawal phase of 20 trials. In Experiment 1, one group (N=15) had visual feedback about the ongoing movement and the other group (N=15) did not. In Experiment 2, one group (N=15) practiced initiating the response in the criterion direction and moving the criterion extent, whereas, the other group (N=15) practiced initiating the response in the criterion direction and moving randomly varied extents. The results of Experiment 1 indicated that the learning of a programmed-based process is a gradually acquired freedom from visual feedback. Experiment 2 revealed that a programmed-based process can be learned independent of a feedback-based process.     

The learning of programmed- and feedback- based processes controlling the production of a positioning response in two dimensions

Two experiments were conducted to investigate the learning of the programmed- and feedback-based processes controlling the production of a slow, self-paced positioning response in two dimensions (direction and extent) in the horizontal plane. Both experiments had two phases: an acquisition phase of 60 trials with KR, followed by a KR withdrawal phase of 20 trials. In Experiment 1, one group (N=15) had visual feedback about the ongoing movement and the other group (N=15) did not. In Experiment 2, one group (N=15) practiced initiating the response in the criterion direction and moving the criterion extent, whereas, the other group (N=15) practiced initiating the response in the criterion direction and moving randomly varied extents. The results of Experiment 1 indicated that the learning of a programmed-based process is a gradually acquired freedom from visual feedback. Experiment 2 revealed that a programmed-based process can be learned independent of a feedback-based process.     

Kinematic information feedback for learning a rapid arm movement

The experiments reported examine the notion that knowledge of results (KR) about the outcome of a response does not provide the necessary information for optimizing performance in many skilled activities. The effect of traditional KR was contrasted with various kinematic feedback parameters in the acquisition of a single degree of freedom response requiring the minimization of movement time. Experiment 1 showed that the presentation of discrete kinematic information feedback (peak accelaration, time to peak accelaration, and velocity at the target location) did not facilitate performance over movement-time KR. Experiment 2 revealed that presentation of a computer generated velocity-time representation of the movement as terminal information feedback improved performance over movement-time KR. This facilitation occured even without knowledge of the kinematics for optimal performance. The findings suggest that the task criterion specifies the appropriate information feedback for skill learning in that the information feedback must match the constraints imposed upon response output.     

The Effect of Erroneous Knowledge of Results on Skill Acquisition when Augmented Information is Redundant

Even though it can be shown that verbal knowledge of results (KR) is redundant with sensory feedback for learning certain motor skills, such findings do not eliminate the possibility that when KR is available it influences underlying learning processes. In order to examine the function of KR more closely, two experiments were designed in which the subjects received conflicting information about their own sensory feedback and the KR presented by the experimenter. In Experiment 1, two erroneous-KR groups, a correct-KR group, and a no-KR group performed 150 practice trials on a simple anticipation timing task and then performed three no-KR retention tests of 30 trials each following intervals of 10 minutes, 1 week, and 1 month. The results supported previous findings that providing correct KR is redundant in anticipation tasks. However, learning was influenced by KR as subjects performed according to the erroneous KR information, thereby ignoring their sensory feedback even after a 1-month interval. In Experiment 2, subjects practised a more complex striking response for the anticipation task for 75 trials and then performed no-KR retention trials either immediately, or 1 day or 1 week later. One of the groups received erroneous KR after 50 practice trials with correct KR. The results confirmed and extended those from Experiment 1, as erroneous KR, even after initial practice with correct KR, influenced retention performance. These results indicate that although KR provides information that is not needed to learn anticipation timing skills, this augmented verbal information is a dominant source of information that influences underlying cognitive processes involved in learning motor skills.     

The dual role of vision in sequential aiming movements

Previous research has demonstrated that movement times to the first target in sequential aiming movements are influenced by the properties of subsequent segments. Based on this finding, it has been proposed that individual segments are not controlled independently. The purpose of the current study was to investigate the role of visual feedback in the interaction between movement segments. In contrast to past research in which participants were instructed to minimize movement time, participants were set a criterion movement time and the resulting errors and limb trajectory kinematics were examined under vision and no vision conditions. Similar to single target movements, the results indicated that vision was used within each movement segment to correct errors in the limb trajectory. In mediating the transition between segments, visual feedback from the first movement segment was used to adjust the parameters of the second segment. Hence, increases in variability that occurred from the first to the second target in the no vision condition were curtailed when visual feedback was available. These results are discussed along the lines of the movement constraint and movement integration hypotheses.     

Information processes in movement learning: capacity and structural interference effects

A series of experiments examined motor learning as an information processing activity occurring within a working short-term memory system and where response-produced feedback and knowledge of results (KR) are used to modify the action plan developed from previous attempts at the movement task. Use of interpolated activities in the KR delay interval allowed inferences to be made regarding the capacity and structural characteristics of these information processes. Results indicated no capacity limitations on the learning process but important structural effects were found. The results supported the idea that response-produced feedback is relatively unimportant as a feedback variable early in learning. Rather, the use of KR at a relatively high level of movement planning appears to be the important information processing activity underlying learning. Finally, the results supported the view that these information processes are related to cognitive problem solving activities.     

Information Processes in Movement Learning

A series of experiments examined motor learning as an information processing activity occurring within a working short-term memory system and where response-produced feedback and knowledge of results (KR) are used to modify the action plan developed from previous attempts at the movement task. Use of interpolated activities in the KR delay interval allowed inferences to be made regarding the capacity and structural characteristics of these information processes. Results indicated no capacity limitations on the learning process but important structural effects were found. The results supported the idea that response-produced feedback is relatively unimportant as a feedback variable early in learning. Rather, the use of KR at a relatively high level of movement planning appears to be the important information processing activity underlying learning. Finally, the results supported the view that these information processes are related to cognitive problem solving activities.     

Learning and performance effects of accurate and erroneous knowledge of results on time perception

Performance feedback (also known as knowledge of results or KR) has both performance and learning effects on many tasks. Earlier studies have demonstrated performance but not learning effects on time perception tasks. In this experiment, we dissociate and identify these two phenomena on two different time perception tasks. Participants were presented with either accurate (100%) or erroneous (80% or 120% of actual performance) KR on either a reproduction or a numerical estimation time perception task. Accurate (100%) KR reduced the group variability and increased the accuracy of response magnitude but left individual variability unchanged. Erroneous (80% or 120%) KR also reduced the group variability while leaving individual variation unchanged, but decreased the true accuracy of the response, with response magnitudes increasing for the 80% KR group and decreasing for the 120% group. Thus external KR that is in conflict with internal time cues overrides these internal cues and dictates response magnitude on these two tasks. Thus KR provides guidance for these behaviors. KR did not reduce the variability (dispersion) of participants' responses, but centered each participant's responses closer to the targeted performance. This decreased group response variability reflected a performance enhancing effect of KR because group response variability increased after KR was withdrawn. In contrast, response magnitudes remained changed for the duration of the post-KR period, indicating that KR also induced a learned response. Thus individual response variability, group response variability and response magnitude represent dissociable features of performance on these time perception tasks.     

Specificity of learning in a video-aiming task: modifying the salience of dynamic visual cues

The authors investigated whether the salience of dynamic visual information in a video-aiming task mediates the specificity of practice. Thirty participants practiced video-aiming movements in a full-vision, a weak-vision, or a target-only condition before being transferred to the target-only condition without knowledge of results. The full- and weak-vision conditions resulted in less endpoint bias and variability in acquisition than did the target-only condition. Going from acquisition to transfer resulted in a large increase in endpoint variability for the full-vision group but not for the weak-vision or target-only groups. Kinematic analysis revealed that weak dynamic visual cues do not mask the processing of other sources of afferent information; unlike strong visual cues, weak visual cues help individuals calibrate less salient sources of afferent information, such as proprioception.     

Specificity of Learning in a Video-Aiming Task: Modifying the Salience of Dynamic Visual Cues

The authors investigated whether the salience of dynamic visual information in a video-aiming task mediates the specificity of practice. Thirty participants practiced video-aiming movements in a full-vision, a weak-vision, or a target-only condition before being transferred to the target-only condition without knowledge of results. The full- and weak-vision conditions resulted in less endpoint bias and variability in acquisition than did the target-only condition. Going from acquisition to transfer resulted in a large increase in endpoint variability for the full-vision group but not for the weak-vision or target-only groups. Kinematic analysis revealed that weak dynamic visual cues do not mask the processing of other sources of afferent information; unlike strong visual cues, weak visual cues help individuals calibrate less salient sources of afferent information, such as proprioception.     

The Role of Task Experience and Prior Knowledge for Detecting Invalid Augmented Feedback while Learning a Motor Skill

Two hypotheses were investigated. These were generated from results reported by Buekers, Magill, and Sneyers (1994) and an uncertainty account of those and other effects on skill learning of erroneous knowledge of results (KR). The first hypothesis proposes that if experienced performers have developed the capability of detecting and correcting errors, then they should not be influenced by erroneous KR in the same way as novices. The second proposes that if information about the invalid feedback is given to subjects prior to the beginning of the practice trials, then the capability for assessing feedback can be accelerated such that subjects who receive this advance information should not be misled by the erroneous KR. The first hypothesis was investigated in Experiment 1 by having subjects practise an anticipation timing task for 450 trials. One group received correct KR on all trials, and another group received no KR. Half of the subjects in each group were unexpectedly switched to erroneous KR after 400 trials. Results indicated that the erroneous KR influenced both groups during acquisition and on a retention test one minute later. However, on a retention test given one week later, only the group that had practised with no KR before being switched to erroneous KR continued to show the negative influence of the invalid KR. The second hypothesis was examined in Experiment 2 by telling subjects prior to beginning practice trials that it was possible that the KR they received would be erroneous. Results showed that this intervention strategy was effective on the no-KR retention tests only for subjects who had no-KR trials alternated with trials on which they received the erroneous KR. The results of these experiments provide evidence that uncertainty about the validity of sensory feedback increases the likelihood that subjects will be misled by invalid augmented feedback. Moreover, this uncertainty can be overcome by increased experience or by providing advance knowledge about the nature of the invalid feedback.