Twiddler Typing: One-Handed Chording Text Entry for Mobile Phones

An experienced user of the Twiddler, a one--handed chording keyboard, averages speeds of 60 words per minute with letter--by--letter typing of standard test phrases. This fast typing rate coupled with the Twiddler's 3x4 button design, similar to that of a standard mobile telephone, makes it a potential alternative to multi--tap for text entry on mobile phones. Despite this similarity, there is very little data on the Twiddler's performance and learnability. We present a longitudinal study of novice users' learning rates on the Twiddler. Ten participants typed for 20 sessions using two different methods. Each session is composed of 20 minutes of typing with multi--tap and 20 minutes of one--handed chording on the Twiddler. We found that users initially have a faster average typing rate with multi--tap; however, after four sessions the difference becomes negligible, and by the eighth session participants type faster with chording on the Twiddler. Furthermore, after 20 sessions typing rates for the Twiddler are still increasing