Comparison of Two Target Selection Methods for Two-Thumb Touchpad Typing

Abstract

As an option for remote text entry, the possibility of bimanual text entry was explored using a touchpad that is called two-thumb touchpad typing (4-T). The design of a 4-T interface presents a few important design options to examine, and one of them is a target selection method. In this study, two 4-T interfaces were designed, called SlideType and FlyType. These interfaces use two different target selection methods, slide-and-click and fly-and-touch, respectively, and their prototypes were implemented using an optical hover-tracking touchpad. An experiment with the prototypes showed that FlyType was faster than SlideType and could achieve a text entry speed over 24 words per minute after practicing 2hr. In addition, a microanalysis of thumb movements during the experiment showed that there are clear quantitative differences between the two methods in the degree of ballisticity of finger motions, in the concurrency of the movements of the two thumbs, and in the degree of integration between reaching and selecting actions, and that FlyType supports a more integral, ballistic, and concurrent motor skill than SlideType.