A Method for Evaluating Head-Controlled Computer Input Devices Using Fitts' Law

Abstract

The discrete movement task employed in this study consisted of moving a cursor from the center of a computer display screen to circular targets located 24.4 and 110.9 mm in eight radial directions. The target diameters were 2.7, 8.1, and 24.2 mm. Performance measures included movement time, cursor path distance, and root-mean-square cursor deviation. Ten subjects with no movement disabilities were studied using a conventional mouse and a lightweight ultrasonic head-controlled computer input pointing device. Average movement time was 306 ms greater (63%) for the head-controlled pointer than for the mouse. The effect of direction on movement time for the mouse was relatively small compared with the head-controlled pointer, which was lowest at 90 and 270 deg, corresponding to head extension and head flexion, respectively. Average path distance and root mean square displacement was lowest at off-diagonal directions (0, 90, 180, and 270 deg). This methodology was also shown to be useful for evaluating performance using an alternative head-controlled input device for two subjects having cerebral palsy, and measured subtle performance improvements after providing a disabled subject with lateral torso support.

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

“…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.…”

Design and validation of a desk-free and posture-independent input device

“…By allowing users to adopt more ergonomic postures, these alternative designs impose a lower risk of CTDs and have been demonstrated to be superior to conventional pointing devices (Straker et al, 2000;Aara˚s et al, 2002;Fagarasanu and Kumar, 2003). Additionally, touchpads on wearable computer when space is unlimited (Tomas et al, 2002), and head-operated pointing devices for subject with disabilities, who move their head in conjunction with their eyes to target letters, have been developed (Radwin et al, 1990;Capilouto et al, 2004). Continuous design efforts are encouraged to provide more ergonomic input to these ubiquitous pointing devices.…”

Hobs

“…Head movement has long been used for virtual camera control in VR applications [15] and as an assistive input technology for cursor control of desktop applications [16]. However, it is notable that human neck muscles have a lower bandwidth than other muscle groups, e.g., the wrist [4].…”