A comparison of two control-display gain measures for head-controlled computer input devices

• Published in: Human factors Vol. 38; no. 3; p. 390
• Main Authors: Schaab, J A, Radwin, R G, Vanderheiden, G C, Hansen, P K
• Format: Journal Article
• Language: English
• Published: United States 01.09.1996
• Subjects: Adult; Ergonomics - instrumentation; Female; Head Movements - physiology; Humans; Least-Squares Analysis; Linear Models; Male; Self-Help Devices; User-Computer Interface
• ISSN: 0018-7208
• DOI: 10.1518/001872096778702042

We compared two gain measures: One, defined as angle/angle (A/A) gain, is the ratio between the angle subtended by displacement of the cursor and the corresponding angle of head extension/flexion or rotation. The alternative measure, defined as displacement/angle (D/A) gain, is the ratio between the linear displacement of the cursor on the screen and the corresponding angle of head extension/ flexion or rotation. A discrete target acquisition task using circular targets was used to compare control-display gain measures. Operator performance was evaluated for three viewing distances and three gain settings of each measure. Average movement time and root mean squared (RMS) cursor deviation from a straight line path increased as viewing distance increased for A/A gain settings 0.75 and 1.0. That no significant distance effect was observed for any of the D/A gain settings indicated that it might be more suitable to fix D/A gain rather than A/A gain for head-controlled computer input devices. Minimum movement time occurred for D/A gain settings of 0.5 cm/degree and 0.67 cm/degree. One explanation for the observed insensitivity of performance to changes in viewing distance with a fixed D/A gain may be that both angular head movement and the accompanying kinesthetic feedback do not change for a specified cursor displacement as viewing distance is changed.