Ergonomics of thumb-based pointing while holding tablets

Interaction in mobile computing mainly relies on selecting targets by touch. A large body of work showed the effect of target size and target distance on selection time. Recent work on hand-held devices suggests that size and distance are not the only factors that affect selection time. In this paper, we investigate target selection performance of the thumb when interacting with grasping hands (see Figure 1). In the first study, we show that the relative direction of the target has a significant effect on selection time. In the second study we show that the direction of movement also has a significant effect. The results extend our knowledge about pointing on hand-held devices and can be used to improve transfer functions of mobile GUIs.