In order to assess if productivity based on extrapolated data is a good predictor of longer texts, an experimental study was conducted. Two full-sized text input devices for touch typing and two miniaturized for tapping were used, all featuing QWERTY layout, in a repeated measurement design. Twenty subjects were exposed to both a task within the limit of working memory (nine words) and four running memory tasks (approx. 275 words). For miniaturized tapping keyboards, extrapolated data significantly underestimated both entry speed (uncorrected wpm, up to 17%) and character error rate (up to 61%) whereas it significantly overestimated ratio of correct words (up to 62%) of running memory tasks. Further, error-corrected entry speed was significantly overestimated up to a factor of 2.7. Results based on extrapolated productivity metrics must therefore be interpreted with caution. Running memory tasks with text length of more than 32 words is needed to assess productivity of text input devices if tapping is used.

Using traditional mobile input devices results in decreased effectiveness and efficiency. To improve usability issues a portable Non-Keyboard QWERTY touch-typing paradigm that supports the mobile touch-typing user is presented and investigated. It requires negligible training time. Pressure sensors strapped to the fingertips of gloves detect which finger is depressed. A language model based on lexical and syntactic knowledge transforms the depressed finger stroke sequence into real words and sentences. Different mobile input QWERTY paradigms (miniaturised, floating and Non-Keyboard) have been compared with full-size QWERTY. Among the mobile input paradigms, the Non-Keyboard fared significantly better, both regarding character error rate and subjective ratings.