Improving Two-Thumb Text Entry on Touchscreen Devices

Antti Oulasvirta, Anna Reichel, Wenbin Li, Yan Zhang, Myroslav Bachynskyi, Keith Vertanen, Per Ola Kristensson

CHI '13: Proceedings of the ACM Conference on Human Factors in Computing Systems, 2013.

We present a split keyboard designed for fast text entry with two thumbs on a 7" mobile touchscreen device. The layout of KALQ was determined through first studying how users should grip a device with two hands. We then assigned letters to keys computationally, using a model of two-thumb tapping. KALQ minimizes thumb travel distance and maximizes alternation between thumbs. An error correction algorithm was added to help address linguistic and motor errors. Users reached a rate of 37 words per minute (a 5% error rate) after a training program.