Prediction of Head Movement Time Using Fitts’ Law

Abstract

Fitts’ movement time prediction equation has been applied and manipulated in analyzing movements of the upper and lower extremities in healthy populations. One common job modification for physically challenged workers is the use of a head or chin stick to depress keys on a keyboard, making use of head movements when movements of the extremities are problematic. The purpose of this research was to assess the applicability of Fitts’ law for the prediction of head movement time. Movement was restricted in healthy subjects by limiting body movement below the neck. Subjects were asked to reciprocally move a chin stylus between targets of various widths and separations. The present study found that Fitts’ law was a robust predictor of head movement time in healthy, college-age males using a chin stylus. Although small within-subjects trends were noted, there were no significant learning effects from Session 1 to Session 2. The mean information-processing rate for the experimental head movement was 7 bits/s, much less than that reported for extremities. These results can provide rehabilitation and industrial engineers valuable insight into the added demands of jobs designed to use repetitive head movements.