A study of direction's impact on single-handed thumb interaction with touch-screen mobile phones

This study is aimed to investigate how the performance of thumb interaction with touch-screen mobile devices via double tap and swipe varies with movement directions of the thumb. A target selection game was used in an empirical study to evaluate users' performance of direction-oriented movements by a thumb on a touch-screen mobile phone in single-handed interaction. The results revealed that single-handed swipe outperformed double tap in terms of speed and accuracy. In addition, angle intervals of thumb moving directions influenced thumb movement accuracy, although there was no significant difference in speed among targets presented with three intervals. Particularly, directions with a 36o interval resulted in the most error-prone task selection for swipe and double tap, and directions with a 45o interval were more error-prone than directions with a 60o interval. Finally, directions of thumb movement did not influence how quickly users could perform double tap or swipe in the areas that were comfortable for the thumb, but they had impact on the accuracy of the two operations. The findings of this study provide new insights for research on single-handed interaction and can be used as guidelines to optimize the design of direction-based applications and interfaces for touch-screen mobile phones.