The main sequence of saccades optimizes speed-accuracy trade-off

Biol Cybern. 2006 Jul;95(1):21-9. doi: 10.1007/s00422-006-0064-x. Epub 2006 Mar 23.


In primates, it is well known that there is a consistent relationship between the duration, peak velocity and amplitude of saccadic eye movements, known as the 'main sequence'. The reason why such a stereotyped relationship evolved is unknown. We propose that a fundamental constraint on the deployment of foveal vision lies in the motor system that is perturbed by signal-dependent noise (proportional noise) on the motor command. This noise imposes a compromise between the speed and accuracy of an eye movement. We propose that saccade trajectories have evolved to optimize a trade-off between the accuracy and duration of the movement. Taking a semi-analytical approach we use Pontryagin's minimum principle to show that there is an optimal trajectory for a given amplitude and duration; and that there is an optimal duration for a given amplitude. It follows that the peak velocity is also fixed for a given amplitude. These predictions are in good agreement with observed saccade trajectories and the main sequence. Moreover, this model predicts a small saccadic dead-zone in which it is better to stay eccentric of target than make a saccade onto target. We conclude that the main sequence has evolved as a strategy to optimize the trade-off between accuracy and speed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / physiology
  • Fixation, Ocular / physiology*
  • Humans
  • Models, Neurological
  • Neural Pathways / physiology
  • Oculomotor Muscles / innervation
  • Oculomotor Muscles / physiology
  • Psychomotor Performance / physiology*
  • Reaction Time / physiology*
  • Saccades / physiology*
  • Time Factors