title: Effects of target height and width on 2D pointing movement duration and kinematics.
abstract: 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.
authors.affiliation: Motor Control Laboratory at Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Bohan
authors.forename: Mitchell G
authors.initials: MG
authors.lastname: Longstaff
authors.forename: Arend W A
authors.initials: AW
authors.lastname: Van Gemmert
authors.forename: Miya K
authors.initials: MK
authors.lastname: Rand
authors.forename: George E
authors.initials: GE
authors.lastname: Stelmach
mesh_terms: D000054:Acceleration; D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D003199:Computer Systems; D006801:Humans; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012016:Reference Values; D012858:Size Perception / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D013647:Task Performance and Analysis