Proceedings: GI 2003

Input-Based Language Modelling in the Design of High Performance Text Input Techniques

William Soukoreff , Scott MacKenzie

Proceedings of Graphics Interface 2003: Halifax, Nova Scotia, Canada, 11 - 13 June 2003, 89-96

DOI 10.20380/GI2003.11

  • BibTeXex

     title = {Input-Based Language Modelling in the Design of High Performance Text Input Techniques},
     author = {R. William Soukoreff and I. Scott MacKenzie},
     booktitle = {Proceedings of the Graphics Interface 2003 Conference, June 11-13, 2003, Halifax, Nova Scotia, Canada},
     organization = {CIPS, Canadian Human-Computer Communication Society},
     publisher = {Canadian Human-Computer Communications Society and A K Peters Ltd.},
     issn = {0713-5424},
     isbn = {1-56881-207-8},
     location = {Halifax, Nova Scotia},
     url = {},
     year = {2003},
     month = {June},
     pages = {89--96}


A new technique to enter text using a mobile phone keypad, Less-Tap, is described. The traditional touch-tone phone keypad is ambiguous for text input because each button encodes 3 or 4 letters. As in Multitap, our method requires the user to press buttons repeatedly to get a required letter. However, in Less-Tap, letters are rearranged within each button according to their frequency. This way, the most common letters require only one key press. Unlike dictionary based methods, Less-Tap facilitates the entry of arbitrary words. Unlike LetterWise and T9, Less-Tap allows entering text without having to visually verify the result, after some initial training. For English, Less-Tap requires an average of 1.5266 keystrokes per character (vs. 2.0342 in Multitap). We conducted a user study to compare Less-Tap against Multitap. Each participant had three 20-minute sessions with each technique. The mean entry speed was 9.5% higher with the new technique.