Tadao Ishikura

Compensatory Coordination of Release Parameters in a Throwing Task

Abstract The consistency and coordination of release parameters in ball-throwing movements were investigated. The authors used a newly developed index of coordination for release parameters (ICRP) that quantifies the degree of improvement of performance consistency caused by compensatory relationships among parameters (i.e., not caused by consistency of parameters). Eight participants practiced for 150 trials, with the nondominant hand, a ball-throwing task aimed at a stationary target. The magnitude of the ball-release velocity vector, among release parameters, as well as the performance was found to become consistent with practice. The ICRP score suggested that the release parameters were complementarily coordinated with one another, and that the coordination improved with practice. Those results indicate that compensatory relationships among varying release parameters contribute to reducing the variability of performance in a ball-throwing task whose goal is accuracy.

EFFECTS OF ANGLE OF MODEL-DEMONSTRATION ON LEARNING OF MOTOR SKILL

The purpose was to examine the effects of three different demonstrations by a model on acquisition and retention of a sequential gross movement task. The second purpose was to examine the relationship between reversal processing of visual information about skills and coding of skill information. Thirty undergraduates (15 men and 15 women) were assigned into one of three conditions, Objective condition which demonstrated the task with the model facing the subject, Looking-glass condition in which the skill was demonstrated with the model facing the subject who viewed the performance opposite the right and left directions in executing the task, and the Subjective condition in which the subject observed the model from the rear. Number of immediate recall tests required to accomplish the sequential movements completely and the sum of the performance points for reproduced movements at each delayed recall test (1 day, 7 days, and 5 mo. after the immediate recall test) were employed. Analysis indicated the Subjective condition produced a significantly greater modeling effect in immediate recall of the movements than the Looking-glass condition. Retention of the acquired skills was almost equal under the three conditions.

Head–Putter Coordination Patterns in Expert and Less Skilled Golfers

The authors examined the patterns of expert and less skilled golfers in putting on an indoor surface to 1 of 3 circular targets (1, 3, and 5 m away) in trials with a ball present (and putted) or not present (a practice stroke). As expected, the experts performed better than the less skilled golfers on a large number of outcome and kinematic measures. Displacement and velocity profiles of the head and putter revealed high positive correlations for the less skilled golfers, indicating a dominant allocentric coordination pattern, but high negative correlations for the expert golfers, indicating a dominant egocentric coordination pattern. The observed coordination patterns did not interact with the distance of the intended putt or the presence/absence of a ball. These findings offer preliminary evidence that, although contrary to traditional beliefs, fundamental differences exist in putting coordination modes between expert and less skilled golfers.

REDUCED RELATIVE FREQUENCY OF KNOWLEDGE OF RESULTS WITHOUT VISUAL FEEDBACK IN LEARNING A GOLF-PUTTING TASK ','

This study examined the effects of reduced relative frequency of knowledge of results (KR) on learning to putt in golf. Participants (19 men and 15 women) putted a golf ball, stopping the ball on a line at a distance of 3.5 m from the starting position, which included an uphill portion. After a pretest, participants were assigned as they arrived in balanced order by sex to one of two groups (100% KR, 33% KR) and practiced 60 trials. Those in the 100% KR group performed the task in its natural context, while others assigned to the 33% KR were shown the location of the putted ball after every third trial. All participants then performed a posttest and two retention tests, done 10 min. and 24 hr. after the posttest. Analysis at posttest showed each group had a constant error and an absolute constant error (|CE|) less than those at pretest. Also, in the retention test conducted the following day, the constant error of the 33% KR group was less than that of the 100% KR group. Third, in the posttest and both retention tests, the |CE| of the 100% KR group was larger than that of the 33% KR group. These results suggest that reduced relative frequency of knowledge of results is effective in learning the accuracy of the golf putt.

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.

Do Expert Golfers Keep Their Heads Still While Putting

The putting patterns of five expert and 11 less-skilled golfers were examined to understand the nature of head movement that occurred during the putting stroke. As expected, the less-skilled golfers moved their heads in the direction of the backswing, then reversed and moved it in the direction of the downstroke during the putt. In contrast, and contrary to expectations, the experts did the reverse – they moved their head in a direction that was opposite to the direction of the putter. The strokes of both the experts and less-skilled golfers revealed closely matched timing constraints, indicating a strong preference to organize these actions as a single coordination pattern

Effects on modeling sequential body movements when viewed from the front or rear.

This study investigated the effect of having a model demonstration viewed from the rear and/or front on the subsequent acquisition of sequential gross-movement patterns, and further examined how participants who observed the bi-angle model directed their attention toward the rear view or the front view in mirror. The movement pattern consisted of seven pauses. A total of 36 participants was divided into three groups: the rear-angle group, which observed the rear view; the front-angle group, which observed from the front view and had to change the motions into their mirror opposites; and the bi-angle group, which observed the rear view and the front view in the mirror. The results showed that (1) all groups acquired the movement pattern, (2) the bi-angle and the rear-angle groups reproduced the demonstrated movement more accurately than the front-angle group, and (3) the bi-angle group tended to focus gaze on viewing the model from the rear. These results suggest that rear viewing was more effective than front viewing, because the participants could simply copy the motion, the bi-angle group members directed their visual attention to the view from the rear without any instruction about observational strategy, and modeling effect was the same for the rear-angle group and the bi-angle group.

The use of knowledge of results based on the stability of performance during acquisition of timing skill: a validity study.

The goal was to examine the effect of changing knowledge-of-results bandwidth based on a participants stable performance during acquisition of a timing skill. 36 university students experienced one of three conditions: (1) 100% KR condition during which information on errors was provided after each trial during practice, (2) fluctuation-of-range condition, wherein KR bandwidth was based on standard deviation of five trials, and (3) 10% KR bandwidth condition (10%), wherein the KR bandwidth was 810–990 msec. Variable error in the fluctuation-of-range condition at posttest and retention was significantly smaller than that with the 100% KR. Conditions in which range of KR was allowed to fluctuate were more effective for stabilizing performance.

DO PARTICIPANTS USE MENTAL ROTATION WHEN COMPARING TWO MODELS FROM DIFFERENT VIEWING ANGLES

This study aimed to examine the role of the viewing angle in determining whether two posed figures are the same or different, in terms of event-related potentials (ERPs) and cognitive load measured via response times. It was hypothesized that an angular difference between poses of 0° would be associated with the shortest reaction times and the largest ERP amplitudes before, and 350 ms after a stimulus presentation. Fourteen healthy male university students (mean age = 22.4 years, SD = 1.4) participated. They were asked to judge whether two figures were posed in the same way or not. The difference in angular rotation between the two figures was 0o, 60o, 120o, or 180o. The angular differences of 0o received the fastest responses. The Pz scalp site had a larger amplitude from 250 ms to 500 ms after stimulus onset than from 500 ms to 600 ms, but there was no effect of the viewing angle. Similarly, the viewing angle was also not distinguished in the pre-response ERP components. These results indicate that since there was no rotation-related negativity in the ERP data, individuals might judge whether two simultaneously presented figures are the same or different without mentally rotating the figures.