The role of feedback in manual tracking of visual targets.
The role of visual feedback in manual tracking was investigated in 24 subjects who tracked 5-, 10-, and 40-mm/diameter targets, moving on a screen at 18 to 25 mm/sec., along various paths, by moving an unseen handle over a digitizing tablet. A cursor indicating instantaneous handle position was visible at all times on half the trials and hidden within a circle coaxial with the target but double its diameter in the other half. The handle had to be within the instantaneous target's digitizer-defined boundaries for the latter to keep moving. All tracking movements were segmented into small movement steps. A tendency to outrun the target was seen, indicating predictive control. Absence of visual feedback had negligible effect on movement velocity. Movement direction appeared to involve open-loop programming but improved significantly when subjects could see the cursor. Occasional corrective movements occurred only when visual feedback was given. Otherwise, a large positional error accumulates despite reasonable ability to control tracking direction.
Faculty of Medicine, Department of Physiology, Technion-Israel Institute of Technology, Israel. shraga@tx.technion.ac.il
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D000328:Adult; D004192:Discrimination, Psychological; D005246:Feedback; D005260:Female; D005556:Form Perception; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D009039:Motion Perception; D009048:Motor Skills; D009949:Orientation; D011597:Psychomotor Performance; D011930:Reaction Time; D012858:Size Perception