Fitts’ Law in Two Dimensions with Hand and Head Movements Movements

Abstract

Subjects performed two-dimensional discrete movements either with a helmet-mounted sight or with a joystick. Fitts' Law was found to be a good predictor of the speed-accuracy tradeoff for both systems. The joystick produced faster movement times than the helmet-mounted sight. For both systems, horizontal and vertical movements were slightly faster than diagonal movements. Two dimensional generalizations of Fitts' Law were discussed in terms of multidimensional scaling. The obtained pattern of movement times was found to be intermediate to the predictions of Euclidean and City-block models of the movement space. Muscle coordination strategies were considered, and a strictly serial coordination model was rejected. A strictly parallel model was also rejected for the helmet-mounted sight, but not for the joystick.

Extending Fitts' law to a three-dimensional pointing task

“…4 (cf., e.g., Jagacinski & Monk, 1985;MacKenzie, 1989MacKenzie, , 1992Boritz et al, 1991;Murata, 1996). Jagacinski and Monk (1985) and Boritz et al (1991) investigated how directional mouse movement affected pointing time and showed that the pointing times differed significantly across conditions of directional movement. In these studies, however, the performance modeling was conducted by pooling all directional mouse movements.…”

“…Although movement direction has some effects on the movement time in two-dimensional tasks (Boritz et al, 1991;Jagacinski & Monk, 1985), there are few explicit models that take these effects into account. However, movement direction seems to be an important factor in performance modeling, especially the modeling of three-dimensional pointing tasks.…”

“…In line with these studies, there have been some attempts to extend Fitts' law to two-dimensional tasks (MacKenzie & Buxton, 1992;Murata, 1996Murata, , 1999, which were aimed at improving the predictive power of modeling the pointing time of mouse operations. Jagacinski and Monk (1985) discussed a two-dimensional generalization of Fitt's law in terms of multidimensional scaling and found that the pattern of movement was intermediate to the predictions of Euclidean and City-block models of movement space. Boritz et al (1991) showed that there was a relationship between movement direction and movement (pointing) time and that this relationship depended on whether the user was right-or left-handed.…”

Case study: Head orientation and neck electromyography for cursor control in persons with high cervical tetraplegia

“…A threshold of 10° off-center was used for head orientation to allow for the few degrees of natural drift that has been observed while individuals attempt to hold their head motionless [20]. The threshold for EMG command onset was fixed at 20 percent of the EMG mvc and included a shifting baseline calculation to account for long-period changes in EMG magnitudes over the course of the experiment.…”

“…However, few computer interfaces applicable to individuals with SCI have been similarly quantified. Headcommanded cursor position control has been investigated by Jagacinski and Monk [20], Radwin et al [21], and LoPresti et al [22][23], with performance assessed using a two-dimensional target-acquisition task similar to the one used in this study. Other than these, rigorous quantitative analysis of computer interfaces specifically applicable to individuals with SCI has not been performed.…”