The information capacity of the human motor system in controlling the amplitude of movement
Fitts asked whether the human motor system has a roughly fixed capacity for handling information when it controls the amplitude of a movement. Sixteen right-handed college men did reciprocal tapping with a stylus at amplitudes from two to sixteen inches and target widths from a quarter of an inch to two inches. A different sixteen men did a disc transfer task, and twenty students, ten men and ten women, did a pin transfer task, with errors not permitted in both transfer tasks. He defined difficulty in bits per response from the ratio of amplitude to tolerance and divided it by average movement time to obtain a rate in bits per second. The rate stayed roughly constant across a central range of amplitudes and tolerances and fell off outside it, and the best rate across the three tasks was about ten to twelve bits per second.
Fitts asked whether the human motor system has a roughly fixed capacity for handling information when it controls the amplitude of a movement. Sixteen right-handed college men did reciprocal tapping with a stylus at amplitudes from two to sixteen inches and target widths from a quarter of an inch to two inches. A different sixteen men did a disc transfer task, and twenty students, ten men and ten women, did a pin transfer task, with errors not permitted in both transfer tasks. He defined difficulty in bits per response from the ratio of amplitude to tolerance and divided it by average movement time to obtain a rate in bits per second. The rate stayed roughly constant across a central range of amplitudes and tolerances and fell off outside it, and the best rate across the three tasks was about ten to twelve bits per second.
Written from the full text, 1992 reprint of the paper, 2026-10-31.
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Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6), 381-391. doi:10.1037/h0055392 https://doi.org/10.1037/h0055392