ABSTRACT
The effect of key size on text entry on a handheld device while walking and standing was examined in order to answer the following questions: 1) Will the additional workload of walking amplify the effect of input difficulty? and 2) Can walking speed be used as a secondary task measure of mental workload during mobile text entry? 13 participants (7 males and 6 females) input well known sayings (sentences) in English into a handheld device in each of four size conditions, with the text input box ranging in width between 2 and 5 millimetres (mm). Text input speed increased with larger size of text box up to a size of 3mm, and text input speed was faster when standing (vs. walking). The effect of size did not depend on whether participants were walking or standing. Errors were significantly higher for the 2mm size condition but did not vary for the wider sizes, while subjective ease of input increased with increasing input box width, only crossing the midpoint of the rating scale (i.e., more easy than difficult) at an input box width of 3mm. Based on these results it is recommended that a minimum text input box width of 3mm be used for handheld text input. Walking speed during text entry in this study was relatively low (with a mean of 1.77 km/h) but width of text input box had no additional effect on walking speed over and above the general slowing caused by text entry. Thus the answers to both of the main questions posed in this study were in the negative, although the fact that people had to enter text slowed walking speed by a fixed amount (independent of level of input difficulty) that varied between individuals. Implications for measuring workload in mobile text entry tasks are discussed.
- Brewster, S., Lumsden, J., Bell, M., Hall, M., and Tasker, S. (2003). Multimodal 'Eyes-Free' Interaction Techniques for Wearable Devices. CHI Letters, 5(1), 473--480. Google ScholarDigital Library
- Fleetwood, M. D., Byrne, M. D., Centgraf, P., Dudziak, K. Q., Lin, B. and Mogilev, D. (2002). An evaluation of text-entry in Palm OS - Graffiti and the virtual keyboard. Proceedings of the Human Factors and Ergonomics Society 46th Annual Meeting, pp. 617--621.Google ScholarCross Ref
- Gould, J. D., Alfaro, L., Finn, R., Haupt, B. and Minuto, A. (1987). Reading from CRT displays can be as fast as reading from paper. Human Factors, 29(5), 497--517. Google ScholarDigital Library
- Griffin M.J. and Hayward, R.A. (1994). Effects of horizontal whole-body vibration on reading. Applied Ergonomics, 25, 165--169.Google ScholarCross Ref
- Hancock, P., and Meshkati, N. (Eds.). (1988). Human Mental Workload. Amsterdam, Netherlands: Elsevier Science Publishers.Google Scholar
- Kahneman, D. (1973). Attention and Effort. Prentice Hall: Englewood Cliffs, NJ.Google Scholar
- Kjeldskov J. and Stage J. (2004) New Techniques for Usability Evaluation of Mobile Systems. International Journal of Human Computer Studies, 60, 599--620.Google ScholarCross Ref
- MacKenzie, I. S, Nonnecke, R. B., McQueen, J. C, Riddersma, S. and Meltz, M. (1994). A comparison of three methods of character entry on pen-based computers. Proceedings of the Human Factors and Ergonomics Society 38th Annual Meeting. pp. 330--334.Google ScholarCross Ref
- Mizobuchi, S., Mori, K., Ren, X. and Yasumura, M. (2002). An Empirical Study of the Minimum Required Size and the Number of Targets for Pen on the Small Display, Proceedings of Mobile HCI 2002, pp.184--194. Springer-Verlag. Google ScholarDigital Library
- Mustonen, T., Olkkonen, M., and Häkkinen, J. (2004). Examining Mobile Phone Text Legibility while Walking. Proceedings of CHI 2004, pp. 1243--1246. N.Y.: ACM Press. Bowman, B., Debray, S. K., and Peterson, L. L. Reasoning about naming systems. ACM Trans. Program. Lang. Syst., 15, 5 (Nov. 1993), 795--825. Google ScholarDigital Library
- Wickens, C., Gordon, S. E. and Liu, Y. (1998). An Introduction to Human Factors Engineering. New York: Longman. Google ScholarDigital Library
Index Terms
- Mobile text entry: relationship between walking speed and text input task difficulty
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