Amy K. Karlson, Benjamin B. Bederson, and Jose Contreras-Vidal
A major challenge faced in the design of mobile devices is that they are typically used when the user has limited physical and attentional resources available. We are interested in the circumstances when a user has only a single hand available. To offer insight for future one-handed mobile designs, we conducted three foundational studies: a field study to capture how users currently operate devices; a survey to record user preference for the number of hands used for a variety of mobile tasks, and an empirical evaluation to understand how device size, target location, and movement direction influence thumb mobility. We have found that one-handed use of keypad-based phones is widespread, and in general, a majority of phone and PDA users would prefer to use one hand for device interaction. Additionally, our results suggest that device size is not a factor in how quickly users can access objects within thumb reach, but that larger devices have more areas that are out of reach, and thus inappropriate for one-handed access. Finally, regardless of device size, diagonal thumb movement in the NW-SE direction is the most difficult movement for right handed users to perform.
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