Karlson, A., Bederson, B. (April 2007)
In this paper, we present ThumbSpace, a software-based interaction technique that provides general one-handed thumb operation of touchscreen-based mobile devices. Our goals are to provide controlled and accurate selection of all interface objects, especially small and far targets, which are traditionally difficult to interact with using the thumb. ThumbSpace is designed to provide these benefits independent of the application design, which can free designers to focus on effective presentation, as well as efficient interaction when two hands are available. We present the ThumbSpace design and a comparative evaluation against direct interaction for target selection. Our results show that in addition to being well received, ThumbSpace improves accuracy for selecting targets that are out of thumb reach, and makes users as effective at selecting small targets as large targets. The results further suggest user practice and strategic design iterations hold potential to close the gap in access time between the two input methods, where ThumbSpace does not do as well as direct interactions.