Experimental Evaluations of the Twiddler One-Handed Chording Mobile Keyboard

Abstract

The HandyKey Twiddler™ is a one-handed chording mobile keyboard that employs a 3 × 4 button design, similar to that of a standard mobile telephone. We present a longitudinal study of novice users' learning rates on the Twiddler. Ten participants typed for 20 sessions using 2 different text entry methods. Each session was composed of 20 min of typing with multitap and 20 min of one-handed chording on the Twiddler. We found that users initially had a faster average typing rate with multitap; however, after 4 sessions the difference became negligible, and by the 8th session participants typed faster with chording on the Twiddler. Five participants continued our study and achieved an average rate of 47 words per minute (wpm) after approximately 25 hr of practice in varying conditions. One participant achieved an average rate of 67 wpm, equivalent to the typing rate of the 2nd author, who has been a Twiddler user for 10 years.We analyze the effects of learning on various aspects of chording, provide evidence that lack of visual feedback does not hinder expert typing speed, and examine the potential use of multicharacter chords (MCCs) to increase text entry speed. Finally, we explore improving novice user's experience with the Twiddler through the use of a chording tutorial.