The Effects of Encumbrance and Mobility on Touch-Based Gesture Interactions for Mobile Phones

In this paper, we investigate the effects of mobility and encumbrance (holding objects such as shopping bags) on standard gestures commonly performed on touchscreens: tapping, dragging, spreading & pinching and rotating clockwise & anticlockwise when completed using a two-handed input posture. These one- and two- finger on-screen gesture inputs have become common but previous research has only examined tapping performance in everyday walking and encumbered situations. Therefore, a series of Fitts' Law style targeting tasks was designed to measure the performance of each gesture with users walking only and walking while carrying bags. The results showed that encumbrance and walking had a negative impact on each gesture in terms of accuracy except for rotational actions, which were performed well. Tapping and dragging both performed poorly which shows the input difficulties of single finger interactions when encumbered and on the move. Our findings will help designers choose the appropriate input techniques for future mobile user interfaces and apps in physically demanding contexts.

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