Evidence for separate control of slow version and vergence eye movements: Support for Hering's law

John L. Semmlow, Weihong Yuan, Tara L. Alvarez

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


When a visual stimulus changes direction and distance simultaneously, Hering's Law argues that the resulting eye movements are the result of combined version and vergence control processes. Recently, it has been suggested that slow asymmetrical eye movements might be guided by monocular control processes wherein each eye is driven by its own retinal image. Experimental results presented here show behavioral differences between slow version and slow vergence eye movements, indicating that different control processes drive the two 'pure' responses. Specifically, version tracking of constant velocity stimuli (i.e., smooth pursuit) is more precise, showing less variation in tracking velocity than movements of equal velocity produced by vergence stimuli. When the two stimuli are combined, the variability in tracking is consistent with the addition of the two components in proportion to their respective stimuli. These results provide support for Hering's Law, at least for low velocity, smooth tracking movements (i.e., slow version and slow vergence).

Original languageEnglish (US)
Pages (from-to)1145-1152
Number of pages8
JournalVision Research
Issue number8
StatePublished - Feb 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems


  • Disparity vergence
  • Eye movement
  • Hering's law
  • Smooth pursuit
  • Vergence


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