Planning multiple movements within a fixed time limit: The cost of constrained time allocation in a visuo-motor task

Hang Zhang, Shih Wei Wu, Laurence T. Maloney

Research output: Contribution to journalArticle

Abstract

S.-W. Wu, M. F. Dal Martello, and L. T. Maloney (2009) evaluated subjects' performance in a visuo-motor task where subjects were asked to hit two targets in sequence within a fixed time limit. Hitting targets earned rewards and Wu et al. varied rewards associated with targets. They found that subjects failed to maximize expected gain; they failed to invest more time in the movement to the more valuable target. What could explain this lack of response to reward? We first considered the possibility that subjects require training in allocating time between two movements. In Experiment 1, we found that, after extensive training, subjects still failed: They did not vary time allocation with changes in payoff. However, their actual gains equaled or exceeded the expected gain of an ideal time allocator, indicating that constraining time itself has a cost for motor accuracy. In a second experiment, we found that movements made under externally imposed time limits were less accurate than movements made with the same timing freely selected by the mover. Constrained time allocation cost about 17% in expected gain. These results suggest that there is no single speed-accuracy tradeoff for movement in our task and that subjects pursued different motor strategies with distinct speed-accuracy tradeoffs in different conditions.

Original languageEnglish (US)
Article number1
JournalJournal of vision
Volume10
Issue number6
DOIs
StatePublished - 2010

Keywords

  • Bayesian decision theory
  • Expected utility
  • Fitt's law
  • Optimality
  • Reaching
  • Touching

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

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