August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Practice does not make perfect: Time allocation in sequential movements
Author Affiliations
  • Hang Zhang
    Department of Psychology, New York University, and Center for Neural Science, New York University
  • Shih-Wei Wu
    Division of the Humanities and the Social Sciences, California Institute of Technology
  • Laurence Maloney
    Department of Psychology, New York University, and Center for Neural Science, New York University
Journal of Vision August 2009, Vol.9, 1167. doi:10.1167/9.8.1167
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      Hang Zhang, Shih-Wei Wu, Laurence Maloney; Practice does not make perfect: Time allocation in sequential movements. Journal of Vision 2009;9(8):1167. doi: 10.1167/9.8.1167.

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Abstract

Dean et al. (2007, JOV/7) found that people could trade off motor uncertainty and movement time to maximize expected gain in an economic task involving a single speeded movement. It came as a surprise that people failed to correctly allocate time between two sequential movements in a similar task (Wu et al. 2007, JOV/6). Why? Perhaps they need to learn how motor uncertainties vary with timings. Or to divide time arbitrarily. We investigated how well people could allocate time in planning a sequence of speeded movements after explicit training in varying timing.

Method: Subjects pointed sequentially to two targets on a touch screen. Successful hits resulted in monetary rewards. There were two sessions. In the practice session, subjects were trained to divide the total movement time (T = 600 ms) in specified ways (Time for the first movement, t1 = 180, 260, 340, or 420 ms). In the following test session, subjects were left to choose freely how to divide the total time. But the rewards for the two targets varied as [10 50], [10 10], or [50 10] points. Four subjects participated, three naïve.

Results: 1) In the practice session, for all subjects, the mean t1/T deviated least from the requirement in the 260/600 condition, and regressed towards 260/600 in the other timing conditions, a tendency hardly affected by practice. 2) In the test session, the three na?ve subjects used a constant time division (close to 260/600) for all three reward conditions, even if other timings they had achieved during practice led to greater expected gains. The non-na?ve subject varied timings but also failed to choose the best available ones. Our results imply that people may not be able to solve problems involving multiple motor uncertainties.

Zhang, H. Wu, S.-W. Maloney, L. (2009). Practice does not make perfect: Time allocation in sequential movements [Abstract]. Journal of Vision, 9(8):1167, 1167a, http://journalofvision.org/9/8/1167/, doi:10.1167/9.8.1167. [CrossRef]
Footnotes
 NIH EY08266
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