Experimental Brain Research

, Volume 207, Issue 1, pp 133–138

Extending Fitts’ Law to three-dimensional obstacle-avoidance movements: support for the posture-based motion planning model


    • Hamilton College
  • Deborah A. Barany
    • Hamilton College
  • Anthony W. Sali
    • Hamilton College
  • Steven A. Jax
    • Moss Rehabilitation Research Institute
  • David A. Rosenbaum
    • Pennsylvania State University
Research Note

DOI: 10.1007/s00221-010-2431-z

Cite this article as:
Vaughan, J., Barany, D.A., Sali, A.W. et al. Exp Brain Res (2010) 207: 133. doi:10.1007/s00221-010-2431-z


According to Fitts’ Law, the time (MT) to move to a target is a linear function of the logarithm of the ratio between the target’s distance and width. Although Fitts’ Law accurately predicts MTs for direct movements, it does not accurately predict MTs for indirect movements, as when an obstacle intrudes on the direct movement path. To address this limitation, Jax et al. (2007) added an obstacle-intrusion term to Fitts’ Law. They accurately predicted MTs around obstacles in two-dimensional (2-D) workspaces, but their model had one more parameter than Fitts’ Law did and was merely descriptive. In this study, we addressed these concerns by turning to the mechanistic, posture-based (PB) movement planning model. The PB-based model accounted for almost as much MT variance in a 3-D movement task as the model of Jax et al., with only two parameters, the same number of parameters as in Fitts’ Law.


Fitts’ lawObstacleMovement timeMotor controlReaching

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© Springer-Verlag 2010