The design and evaluation of a high-performance soft keyboard

The design and evaluation of a high performance soft keyboardfor mobile systems are described. Using a model to predict theupper-bound text entry rate for soft keyboards, we designed akeyboard layout with a predicted upper-bound entry rate of 58.2wpm. This is about 35% faster than the predicted rate for a QWERTYlayout. We compared our design (OPTI) with a QWERTY layout in alongitudinal evaluation using five participants and 20 45-minutesessions of text entry. Average entry rates for OPT1 increased from17.0 wpm initially to 44.3 wpm at session 20. The average ratesexceeded those for the QWERTY layout after the 10 session (about 4hours of practice). A regression equation (R = .997) in the form ofthe power-law of learning predicts that our upper-bound predictionwould be reach at about session 50.