LAUSR

Abstract Much is known about leg/foot movement times when there is a single target constraint - that in the direction of the movement. We report two experiments that investigated the effects of an additional constraint that was perpendicular to the direction of the movement. In Experiment 1, a standard Fitts' task was used but with targets that varied in height and, in Experiment 2, we used the Drury tracking task of moving between lines of varying track widths. Results were different to those of arm/hand movements. In experiment 1 the effects of the Indexes of Difficulty (ID) in the direction of, and perpendicular to, the movement direction, were linearly additive. This is compared to the ‘greater ID model’ that gives a good description of arm movements. When tracking between parallel lines, foot performance is poor compared to arm performance when error rates are controlled. The Drury model well describes data for arm and foot movements, when the error rates are controlled, but initial error rates increase rapidly with decrease of target width and hence the leg/foot system has difficulty in control at higher values of amplitude to track width ratio. Relevance to industry The foot is commonly used for controlling a device. This research demonstrates the effect of having limited width of a target perpendicular to the direction of movement of the foot/leg. Performance is compared to that of the hand/arm system.