Seijiro Tsutsui

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.

Contextual Interference in Learning New Patterns of Bimanual Coordination

Two experiments are reported in which the question of whether or not contextual interference effects are found in motor tasks that require the acquisition of new coordination patterns was examined. Participants (N = 18, Experiment 1; N = 12, Experiment 2) practiced 3 novel bimanual patterns (45 degrees , 90 degrees , and 135 degrees relative phase) in either a random or a blocked order. No statistically significant acquisition or retention differences between groups were found when all 3 patterns were practiced on each of 2 days (Experiment 1). When the blocked group practiced 1 pattern on each of 3 acquisition days (Experiment 2), however, typical contextual interference effects were found: The blocked group performed better than the random group in practice, but the random group performed better than the blocked group in a delayed (by I week) retention test. The experiments revealed that contextual interference effects can arise in motor tasks that require the acquisition of new coordination patterns and are not limited to tasks involving novel scaling of a previously existing pattern.

Effect of Manual Guidance on Acquiring a New Bimanual Coordination Pattern

Guidance is a procedure used to help learners experience a proprioceptive sensation arising from correct movements and preventing learners from being exposed to dangerous situations. Early research on guidance done by Armstrong (1970) examined the effects of terminal feedback, concurrent feedback, and physical guidance using a task to move a lever through a particular spatial-temporal pattern. Participants of a terminal-augmented feedback group received knowledge of performance after each trial but were not allowed to see their own movements. Participants of a concurrent augmented feedback group were allowed to see their movements. Participants of a guidance group mechanically controlled their movement using a device such that physically corrected any deviations from the target path. A transfer test without augmented feedback was used after practicing for 3 days. In the acquisition trials, the guidance group performed the elbow movements almost perfectly because of the machine assistance. The concurrent feedback group also performed the task well, whereas the terminal feedback group performed the task with greater error (root mean square error) than the other two groups. However, in the retention test, the terminal feedback group was superior in performance to both the concurrent feedback

Constrained paths based on the Farey sequence in learning to juggle

In this article we report the results of a study conducted to investigate the learning dynamics of three-ball juggling from the perspective of frequency locking. Based on the Farey sequence, we predicted that four stable coordination patterns, corresponding to dwell ratios of 0.83, 0.75, 0.67, and 0.50, would appear in the learning process. We examined the learning process in terms of task performance, taking into account individual differences in the amount of learning. We observed that the participants acquired individual-specific coordination patterns in a relatively early stage of learning, and that those coordination patterns were preserved in subsequent learning, even though performance in terms of number of successful consecutive throws increased substantially. This increase appeared to be related to a reduction in spatial variability of the juggling movements. Finally, the observed coordination patterns were in agreement with the predicted patterns, with the proviso that the pattern corresponding to a dwell ratio of 0.50 was not realized and only a hint of evidence was found for the dwell ratio of 0.67. This implies that the dwell ratios of 0.83 and 0.75 in particular exhibited a stable coordination structure due to strong frequency locking between the temporal variables of juggling.