effect of control-to-display gain and movement direction of information spaces on the usability of navigation on small touch-screen interfaces using tap-n-drag

tap-n-drag is a popular navigation method for small touch-screen interfaces. when an information space is too large compared to the touch-screen size, navigating the information space using tap-n-drag requires too many drags, resulting in poor usability such as long navigation time or fatigue. in this study, the effect of control-to-display gain on the usability of tap-n-drag was experimentally investigated to determine whether increasing the control-to-display gain can resolve this problem. the effect of movement direction of the information space relative to the drag direction was also investigated (push background vs. push viewport). in experiments, increasing control-to-display gain seemed to increase the usability of tap-n-drag, but excessively large gain seemed to have the opposite effect on some measures such as task completion time, ease of use and overall preference; as a result these measures-vs.-gain curves were u-shaped or inverted-u-shaped. overall, both task completion time and number of touches required to locate a target were lower when using push viewport than when using push background, except at gain = 1.