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Roland van den Tillaar

different trade-offs between velocity and accuracy based on different theoretical principles ( Fitts, 1954 ; Plamondon & Alimi, 1997 ; Sherwood & Schmidt, 1980 ). For example, Fittslaw ( 1954 ), based on principles of limited processing capacity, showed a logarithmic function between speed and accuracy

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Mark L. Latash and Irina L. Mikaelian

We explored the relations between task difficulty and speech time in picture description tasks. Six native speakers of Mandarin Chinese (CH group) and six native speakers or Indo-European languages (IE group) produced quick and accurate verbal descriptions of pictures in a self-paced manner. The pictures always involved two objects, a plate and one of the three objects (a stick, a fork, or a knife) located and oriented differently with respect to the plate in different trials. An index of difficulty was assigned to each picture. CH group showed lower reaction time and much lower speech time. Speech time scaled linearly with the log-transformed index of difficulty in all subjects. The results suggest generality of Fitts’ law for movement and speech tasks, and possibly for other cognitive tasks as well. The differences between the CH and IE groups may be due to specific task features, differences in the grammatical rules of CH and IE languages, and possible use of tone for information transmission.

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Howard N. Zelaznik

concerned with the nature of the speed accuracy trade-off in manual control ( Fitts, 1954 ; Meyer et al., 1982 ; Schmidt et al., 1979 ). In two experiments participants were required to perform several Fittslaw tasks as well as linear speed accuracy trade-off tasks. The Fitts tasks required individuals

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Marcos Duarte and Sandra M.S.F. Freitas

We investigated the speed and accuracy of fast voluntary movements performed by the whole body during standing. Adults stood on a force plate and performed rhythmic postural movements generating fore and back displacements of the center of pressure (shown as online visual feedback). We observed that for the same target distance, movement time increased with the ratio between target distance and target width, as predicted by Fitts’–type relationships. For different target distances, however, the linear regressions had different slopes. Instead, a single linear relation was observed for the effective target width versus mean movement speed. We discuss this finding as a result of the pronounced inherent variability of the postural control system and when such a source of variability is considered, the observed relationship can be explained. The results reveal that the accuracy of fast voluntary postural movements is deteriorated by the variability due to sway during standing.

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Michael Bohan, Mitchell G. Longstaff, Arend W.A. Van Gemmert, Miya K. Rand, and George E. Stelmach

This study examined the impact of target geometry on the trajectories of rapid pointing movements. Participants performed a graphic point-to-point task using a pen on a digitizer tablet with targets and real time trajectories displayed on a computer screen. Circular- and elliptical-shaped targets were used in order to systematically vary the accuracy constraints along two dimensions. Consistent with Fitts' Law, movement time increased as target difficulty increased. Analysis of movement kinematics revealed different patterns for targets constrained by height (H) and width (W). When W was the constraining factor, movements of greater precision were characterized by a lower peak velocity and a longer deceleration phase, with trajectories that were aimed relatively farther away from the center of the target and were more variable across trials. This indicates an emphasis on reactive, sensory-based control. When H was the constraining factor, however, movements of greater precision were characterized by a longer acceleration phase, a lower peak velocity, and a longer deceleration phase. The initial trajectory was aimed closer to the center of the target, and the trajectory path across trials was more constrained. This suggests a greater reliance on both predictive and reactive control.

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Robert W. Christina

By 1967, motor control and learning researchers had adopted an information processing (IP) approach. Central to that research was understanding how movement information was processed, coded, stored, and represented in memory. It also was centered on understanding motor control and learning in terms of Fitts’ law, closed-loop and schema theories, motor programs, contextual interference, modeling, mental practice, attentional focus, and how practice and augmented feedback could be organized to optimize learning. Our constraints-based research from the 1980s into the 2000s searched for principles of “self-organization”, and answers to the degrees-of-freedom problem, that is, how the human motor system with so many independent parts could be controlled without the need for an executive decision maker as proposed by the IP approach. By 2007 we were thinking about where the IP and constraints-based views were divergent and complementary, and whether neural-based models could bring together the behavior and biological mechanisms underlying the processes of motor control and learning.

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M.A. Urbin, David Stodden, Rhonda Boros, and David Shannon

The purpose of this study was to examine variability in overarm throwing velocity and spatial output error at various percentages of maximum to test the prediction of an inverted-U function as predicted by impulse-variability theory and a speed-accuracy trade-off as predicted by Fitts’ Law Thirty subjects (16 skilled, 14 unskilled) were instructed to throw a tennis ball at seven percentages of their maximum velocity (40–100%) in random order (9 trials per condition) at a target 30 feet away. Throwing velocity was measured with a radar gun and interpreted as an index of overall systemic power output. Within-subject throwing velocity variability was examined using within-subjects repeated-measures ANOVAs (7 repeated conditions) with built-in polynomial contrasts. Spatial error was analyzed using mixed model regression. Results indicated a quadratic fit with variability in throwing velocity increasing from 40% up to 60%, where it peaked, and then decreasing at each subsequent interval to maximum (p < .001, η2 = .555). There was no linear relationship between speed and accuracy. Overall, these data support the notion of an inverted-U function in overarm throwing velocity variability as both skilled and unskilled subjects approach maximum effort. However, these data do not support the notion of a speed-accuracy trade-off. The consistent demonstration of an inverted-U function associated with systemic power output variability indicates an enhanced capability to regulate aspects of force production and relative timing between segments as individuals approach maximum effort, even in a complex ballistic skill.

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Alessia Longo and Ruud Meulenbroek

a single unit. Kelso demonstrated that the overriding tendency to generate synchronous movements in bimanual tasks by in-phase or antiphase coordination moderates Fittslaw: Even when the movement distances and/or target widths for both hands differ, their MTs are not likely to deviate to the

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Sergio L. Molina and David F. Stodden

practices of practitioners (e.g., physical educators, coaches, and other movement educators). Fittslaw ( 1954 ) and its application, the speed-accuracy trade-off, are well-known principles that can be applied to many fundamental movements and performance ( Urbin, Stodden, Fischman, & Weimer, 2011

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Marlowe Pecora, Luc Tremblay, and Matthew Heath

002219900218 10.1007/s002219900218 de Grosbois , J. , Heath , M. , & Tremblay , L. ( 2015 ). Augmented feedback influences upper limb reaching movement times but does not explain violations of Fittslaw . Frontiers in Psychology, 6, 800 . PubMed ID: 26136703 doi:10.3389/fpsyg.2015.00800 10