ABSTRACT
This paper developed new techniques to press touch keys that are located at difficult areas to press and evaluated the usability of the new techniques in mobile devices. Two techniques involve pointing to the touch key in the upper left-hand corner of screen when the user uses only one-handed. When the user drags the display with his or her finger, the first technique rearranges the touch key positions for easy selection. The second technique involves the creation of an assisted cursor in the upper left area of the screen when the user touches a point in the lower right-hand area of the screen. The user then selects the touch key with the assisted cursor. A within-subject design was used in an experiment, in which one within-subject variable (three levels: the traditional manner and the two proposed manners) was manipulated. A total of 24 subjects in their 20s participated in the experiment. The experimental task was to press the touch key as quickly and accurately as possible when the target key appeared on the screen using the different techniques. We collected three objective measures: task completion time, number of errors, and number of re-grips. The results showed that the proposed method resulted in a better performance in terms of number of re-grips, but a worse performance in terms of task completion time. The results of this study can be used to design user interfaces for touch screen mobile devices with large screens.
