Early correction of human goal-directed movement

Oh-Sang Kwon, Purdue University

Abstract

Beginning with the seminal work by Woodworth (1899), a two-component hypothesis has been the dominant view of human goal-directed movement (Elliott et al., 2001). According to the hypothesis, a goal-directed movement consists of two phases, namely the “initial impulse” phase and the “current control” phase. In the initial impulse phase the effector approaches the target area under control of centrally programmed ballistic movement. In the current control phase the effector lands at the target under the guide of visual feedback. In this dissertation, I claim that the initial impulse phase of the two-component hypothesis is not really ballistic, but there exists early correction. First, a simulation experiment was performed to demonstrate the usefulness of early correction. Specifically, it was tested when and where in the movement trajectory the most efficient corrections are. Results show that (i) if a single correction is allowed, the correction is most efficient when it is made at the very early stage of movement, and (ii) when two corrections are allowed, the first correction is at the very early stage and the second correction is at the very late stage of movement. These results imply that an early correction is not only useful but also optimal, which is contrary to the commonly accepted claim that an early correction would not be useful due to the small variability of the effector position in the early stage of movement. Second, kinematic profiles of human goal-directed movement were measured in unconstrained and constrained (single joint) experimental settings. Results showed that the estimated correction points are distributed in the very beginning and the end of movement, and that the measured kinematic profiles of human movement are consistent with the simulated kinematic profiles. Based on the simulation results and the empirical data, I suggest that the human goal-directed movement can be better described by a three-component model with early correction than the two-component model of Woodworth.

Degree

Ph.D.

Advisors

Zelaznik, Purdue University.

Subject Area

Behavioral psychology

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