Detecting and correcting errors in rapid aiming movements: effects of movement time, distance, and velocity.

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal that serves as a basis for a correction. The main question addressed in the current study was how distance, movement time, and velocity influence both spatial or temporal error detection. Forty college-aged participants (30 women and 10 men) performed rapid aiming movements over 30 degrees or 50 degrees in either 210 ms or 350 ms without vision. The participants verbally estimated the distance moved and the movement time during acquisition before knowledge of results was given and during an immediate retention test without knowledge of results. Spatial and temporal objective-subjective correlations were greater in the 210-ms condition compared to the 350-ms condition, but were not related to movement velocity.

Spatial error detection in rapid unimanual and bimanual aiming movements.

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal which serves as a basis for a correction. The current study assessed whether error detection is less accurate when feedback from both hands must be analyzed compared to one hand and if error detection is more accurate in longer movements compared to shorter movements. 36 college-age participants (26 women and 10 men) performed a rapid aiming movement of varying distances with one hand or both hands simultaneously. Participants verbally estimated the distance moved on all trials before knowledge of results was given. Error detection was measured by the correlation and the mean absolute difference between the actual and estimated distance. Error detection was not more accurate for the longer movements, and participants underestimated errors in all conditions. Strong positive correlations were shown for both unimanual and bimanual aiming tasks, suggesting that two streams of sensory information can be processed concurrently.

Speed-accuracy tradeoffs in rapid bimanual aiming movements.

Two experiments reported the effect of movement time and knowledge of results on overall spatial errors in rapid simultaneous bimanual aiming movements. In Exps. 1 (n=32) and 2 (n=32), participants used light, aluminum levers oriented vertically in the sagittal plane to make reversal movements over the same distance (20 degrees - 20 degrees or 60 degrees - 60 degrees) or different distances (20 degrees - 60 degrees) in each arm in 250, 350, or 450 msec. to the reversal point. The participants in Exp. 1 were given knowledge of results on the spatial and temporal accuracy for both arms, while in Exp. 2 knowledge of results was provided for one arm only. Strong speed-accuracy tradeoffs were shown for all groups in both experiments, but errors were larger in the different distance movements compared to the same distance groups. Spatial errors were also elevated in Exp. 2 when knowledge of results was not available compared to those conditions where knowledge of results was available. Overall, bimanual speed-accuracy tradeoffs are similar to single arm movements when one moves the same distance in each arm and when knowledge of results is available.