Tactile feedback contributes to consistency of finger movements during typing.

Touch typing movements are typically too brief to use on-line feedback. Yet, previous studies have shown that blocking tactile feedback of the fingertip of typists leads to an increase in typing errors. To determine the contribution of tactile information to rapid fine motor skills, we analyzed kinematics of the right index finger during typing with and without tactile feedback. Twelve expert touch typists copy-typed sentences on a computer keyboard without vision of their hands or the computer screen. Following control trials, their right index fingertip was anesthetized, and sentences were typed again. The movements of the finger were recorded with an instrumented glove and electromagnetic position sensor. During anesthesia, typing errors of that finger increased sevenfold. While the inter-keypress timing and average kinematics were unaffected, there was an increase in variability of all measures. Regression analysis showed that endpoint variability was largely accounted for by start location variability. The results suggest that tactile cues provide information about the start location of the finger, which is necessary to perform typing movements accurately.