title: Performance limitations from delay in human and mechanical motor control.
abstract: We discuss natural limitations on motor performance caused by the time delay required for feedback signals to propagate within the human body or mechanical control systems. By considering a very simple delayed linear servomechanism model, we show there exists a best possible speed-accuracy trade-off similar to Fitts' law that cannot be exceeded when delay is present. This is strictly a delay effect and does not occur for the ideal case of instantaneous feedback. We then examine the performance of the vector integration to endpoint (VITE) circuit as a model of human movement and show that when this circuit is generalized to include delayed feedback the performance may not exceed that of the servomechanism with an equal delay. We suggest the existence of such a limitation may be a ubiquitous consequence of delay in motor control with the implication that the index of performance in Fitts' law cannot arbitrarily large.
authors.affiliation: Chinese Academy of Science, Academy of Mathematics and Systems Science, Beijing, China. dan.beamish@gmail.com
authors.forename: Dan
authors.initials: D
authors.lastname: Beamish
authors.forename: Shabana
authors.initials: S
authors.lastname: Bhatti
authors.forename: Jianhong
authors.initials: J
authors.lastname: Wu
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Jing
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena / Q000379:methods; D002490:Central Nervous System / Q000502:physiology*; D005246:Feedback / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors