Michael Bohan

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We examined whether coordination between movement components during trunk-assisted prehension was compromised in PD patients in response to varying constraints (experiment 1: reach speed, object size, movement amplitude; experiment 2: movement sequence). In general, both PD patients and controls responded similarly to the changes in these three variables.(More)
The current experiment suggests that the speed/accuracy tradeoff is composed of two classes of constraints, effector and task. We examined the effects of movement distance, target size, orientation of the movement in the workspace, and C-D gain on the kinematics of discrete pointing movements made with computer mouse. It was found that target size(More)
Modern tools often separate the visual and physical aspects of operation, requiring users to manipulate an instrument while viewing the results indirectly on a display. This can pose usability challenges particularly in applications, such as laparoscopic surgery, that require a high degree of movement precision. Magnification used to augment the view and,(More)
This study compared text entry performance of two stylus-driven soft keyboards for use in hand-held computing devices: the QWERTY and the T9. Participants transcribed text presented on a computer screen into a personal digital assistant (PDA) using a stylus and one of these two keyboards. We introduced a new psychophysical technique for measuring(More)
This study examined the impact of movement scale and joint set on the trajectories of rapid pointing movement made with a mouse. Participants manipulated a mouse to point a cursor to targets on a display of varying size and distance. The mouse movement was scaled independently of the display size by varying the control gain. Large-scale movements involving(More)
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(More)
Imagery practice of motor tasks has been recommended for a wide range of activities as from flight training to basketball. A key question, both from a practical and a theoretical standpoint, is when during the learning process does imagery practice confer the most benefit? However, the literature does not provide clear guidance, in part because of(More)
This paper reports a preliminary investigation of diffemnt methods for target selection on a computer screen using a mouse. Specifically, an experiment compared the standard point-and-click method to a mouse-over method, whereby the target was automatically selected atIer the cursor and target were superpositioned for 200 ms. Results indicated that the(More)
Recent work has emphasized the distinction between task and effector constraints underlying performance in Fitts' type discrete pointing tasks. We explored the relative contributions of these constraints in a cursor-pointing task by manipulating the control-display scale, thereby dissociating movement scale at the level of the hand from movement scale at(More)
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