Evaluating one handed thumb tapping on mobile touchscreen devices

In spite of the increasing popularity of handheld touchscreen devices, little research has been conducted on how to evaluate and design one handed thumb tapping interactions. In this paper, we present a study that researched three issues related to these interactions: 1) whether it is necessary to evaluate these interactions with the preferred and the non-preferred hand; 2) whether participants evaluating these interactions should be asked to stand and walk during evaluations; 3) whether targets on the edge of the screen enable participants to be more accurate in selection than targets not on the edge. Half of the forty participants in the study used their non-preferred hand and half used their preferred hand. Each participant conducted half of the tasks while walking and half while standing. We used 25 different target positions (16 on the edge of the screen) and five different target sizes. The participants who used their preferred hand completed tasks more quickly and accurately than the participants who used their non-preferred hand, with the differences being large enough to suggest it is necessary to evaluate this type of interactions with both hands. We did not find differences in the performance of participants when they walked versus when they stood, suggesting it is not necessary to include this as a variable in evaluations. In terms of target location, participants rated targets near the center of the screen as easier and more comfortable to tap, but the highest accuracy rates were for targets on the edge of the screen.