Proceedings: GI 2002

A Model of Two-Thumb Text Entry

Scott MacKenzie, William Soukoreff

Proceedings of Graphics Interface 2002: Calgary, Alberta, Canada, 27 - 29 May 2002, 117-124

DOI 10.20380/GI2002.14

  • BibTeX

     title = {A Model of Two-Thumb Text Entry},
     author = {I. Scott MacKenzie and R. William Soukoreff},
     booktitle = (Proceedings of the Graphics Interface 2002 Conference, May 27-29, 2002, Calgary, Alberta, Canada},
     url = {},
     year = {2002},
     month = {May},
     location = {Calgary, Alberta},
     pages = {117--124}


Although text entry has been extensively studied for touch typing on standard keyboards and finger and stylus input on soft keyboards, no such work exists for two-thumb text entry on miniature Qwerty keyboards. In this paper, we propose a model for this mode of text entry. The model provides a behavioural description of the interaction as well as a predicted text entry rate in words per minute. The prediction obtained is 60.74 words per minute. The prediction is based solely on the linguistic and motor components of the task; thus, it is a peak rate for expert text entry. A detailed sensitivity analysis is included to examine the effect of changing the model's components and parameters over a broad range (+/-50% for the parameters). The model demonstrates reasonable stability - predictions remain within about 10% of the value just cited.