August 2009
Volume 9, Issue 8
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Response to changes in variability during movement under risk
Author Affiliations
  • Michael S. Landy
    Dept. of Psychology, NYU, and Center for Neural Science, NYU
  • Nathaniel Daw
    Dept. of Psychology, NYU, and Center for Neural Science, NYU
  • Julia Trommershäuser
    Dept. of Psychology, University of Giessen
Journal of Vision August 2009, Vol.9, 1099. doi:
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      Michael S. Landy, Nathaniel Daw, Julia Trommershäuser; Response to changes in variability during movement under risk. Journal of Vision 2009;9(8):1099.

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      © ARVO (1962-2015); The Authors (2016-present)

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Humans account optimally, or nearly so, for visuomotor variability (Trommershäuser et al., JOSA A 20, 2003) during movement under risk, even when variability is artificially increased (Trommershäuser et al., J Neurosci 25, 2005). How do humans estimate task-related variability in a dynamic, volatile environment in which variability changes? Methods: Subjects pointed rapidly at a target (a tall, green rectangle) on a visual touchscreen display. A small white circle indicated where the finger landed, and a blue circle was also displayed, randomly displaced horizontally from the white square. Displacements were drawn from a zero-mean normal distribution whose standard deviation remained constant for a sequence of trials (random epoch lengths: 75–150 trials) then suddenly changed to a new value (3.7–18.4 mm). Instructions indicated that outcome variability followed such a random sample-and-hold trajectory. On 2/3 of trials, an overlapping, horizontally displaced, red penalty rectangle was also displayed. Subjects won a point (4¢) if the blue square landed on the target, but lost 5 points if it landed on the penalty region. Observers should thus aim further from the penalty area when displacements are larger. Slow movements ([[gt]] 400 ms) were penalized 10 points. Results: 5 of 6 subjects took changing variability into account in planning movement. Actual movement endpoints (where the finger landed) were significantly correlated (p Conclusion: Subjects dynamically estimate movement outcome variability over a windowed running average of previous outcomes.

Landy, M. S. Daw, N. Trommershäuser, J. (2009). Response to changes in variability during movement under risk [Abstract]. Journal of Vision, 9(8):1099, 1099a,, doi:10.1167/9.8.1099. [CrossRef]
 NIH EY08266 to MSL Deutsche Forschungsgemeinschaft (Emmy-Noether-Programme grant TR 528/1-4) to JT.

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