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David E Sherwood

Publications and source records attributed to David E Sherwood.

6 recordsLinked to original sources
PubMed2006

Intermovement interval and spatial assimilation effects in sequential bimanual and unimanual movements.

This study extended earlier work by showing spatial assimilations in sequential bimanual and unimanual movements separated by 1.5-3.5 s. In Experiments 1 and 2, 30 right-handed participants (18-22 years of age) made rapid single and bimanual lever reversals of 20 degrees and 60 degrees assigned to 1.5, 2.5, or 3.5 s intermovement interval groups. Participants self-timed the intermovement interval in the first experiment, but it was provided in the second experiment using separate auditory stimuli. In the third experiment, participants performed both the 20 degree and 60 degree movement with the same hand. In all experiments, the shorter-distance limb overshot and the longer-distance limb undershot the targets in both bimanual and unimanual sequential movements relative to single movements in all three intermovement interval groups, particularly in the non-dominant left limb. The results suggest that assimilation effects in sequential movements are caused by command interactions at the planning level, but the effects are reduced by practice.

Adolescent↗
PubMed2005

Speed-accuracy tradeoffs in rapid bimanual aiming movements.

Two experiments reported the effect of movement time and knowledge of results on overall spatial errors in rapid simultaneous bimanual aiming movements. In Exps. 1 (n=32) and 2 (n=32), participants used light, aluminum levers oriented vertically in the sagittal plane to make reversal movements over the same distance (20 degrees - 20 degrees or 60 degrees - 60 degrees) or different distances (20 degrees - 60 degrees) in each arm in 250, 350, or 450 msec. to the reversal point. The participants in Exp. 1 were given knowledge of results on the spatial and temporal accuracy for both arms, while in Exp. 2 knowledge of results was provided for one arm only. Strong speed-accuracy tradeoffs were shown for all groups in both experiments, but errors were larger in the different distance movements compared to the same distance groups. Spatial errors were also elevated in Exp. 2 when knowledge of results was not available compared to those conditions where knowledge of results was available. Overall, bimanual speed-accuracy tradeoffs are similar to single arm movements when one moves the same distance in each arm and when knowledge of results is available.

Acceleration↗
PubMed2003

Schema theory: critical review and implications for the role of cognition in a new theory of motor learning.

This paper is based on a symposium celebrating the 26th anniversary of the publication of "A Schema Theory of Discrete Motor Skill Learning" (Schmidt, 1975) held at the annual conference of the North American Society for the Psychology of Sport and Physical Activity in June 2001. We provide a brief historical context for schema theory and a review of the development of the mechanistic approach to motor learning in general. We explore recent findings in mental practice, observational learning, augmented feedback presentation, and the variability of practice that are inconsistent with schema theory and provide a rationale for the importance of cognitive activity in motor learning.

Child↗
PubMed2002

Anticipatory modulation of precision grip force with variations in limb velocity of a curvilinear movement.

The authors examined the relationship between peak velocity of a discrete horizontal elbow flexion movement in which the hand path was curvilinear and premovement modulation of precision grip force. The velocity of the movements of 7 participants was varied from maximal velocity to a velocity that required several seconds to reach a target. An object instrumented with force transducers for the forefinger and thumb measured precision grip force. There was a positively accelerating quadratic relationship between grip force change before movement and peak velocity of the ensuing limb movement. On some low-velocity trials, premovement grip force modulation reflected a net decrease. In contrast, high-velocity trials were preceded by net increases in grip force. Using cluster analysis, the authors classified grip forces in low-velocity movements as an empirically distinct set of entities from grip forces in high-velocity movements. The cluster of high-value grip forces suggested an anticipatory strategy that allowed participants a large safety margin in grip force to avoid object slip on movement initiation. The cluster of low-value grip forces at movement initiation suggested a second anticipatory strategy in which participants changed grip force very little, perhaps to increase the ability of proprioceptors in the hand to sense force changes. Those findings suggest that modulation of grip force before initiation of movements in which the hand path is curvilinear may be governed by two distinct velocity-dependent anticipatory strategies.

Adolescent↗