title: Assessment of Fitts' law for quantifying combined rotational and translational movements.
abstract: OBJECTIVE
  To develop a model for human performance in combined translational and rotational movements based on Fitts' law.
  
  
  BACKGROUND
  Fitts' law has been successfully applied to translational movements in the past, providing generalization beyond a specific task as well as performance predictions. For movements involving both translations and rotations, no equivalent theory exists, making comparisons of input devices for these movements more ambiguous.
  
  
  METHODS
  The study consisted of three experiments. In the first two, participants performed either pure translational or pure rotational movements of 1 degree of freedom. The third experiment involved the same movements combined.
  
  
  RESULTS
  On average, the performance times for combined movements were equal to the sum of the times for equivalent separate rotational and translational movements. A simple Fitts' law equivalent for combined movements with a similar slope as the separate components was proposed. In addition, a significant degree of coordination of the combined movements was found. This had a strong bias toward a parallel execution in 12 out of 13 participants.
  
  
  CONCLUSIONS
  Combined movements with rotations and translations of 1 degree of freedom can be approximated using a simple Fitts' law equivalent. The rotational and translational components appear to be coordinated by the central nervous system to generate a parallel execution.
  
  
  CONCLUSIONS
  The results may help drive human interface designs and provide insights into the coordination of combined movements. Future extensions may be possible for the movements of higher degrees of freedom used in robot teleoperation and virtual reality applications.
authors.affiliation: Neutral Buoyancy Research Facility, 382 Technology Drive, University of Maryland, College Park, Space Systems Laboratory, MD 20742, USA.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Stoelen
authors.forename: David L
authors.initials: DL
authors.lastname: Akin
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003626:Data Display; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D008960:Models, Psychological; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012399:Rotation; D014584:User-Computer Interface; D055815:Young Adult