Ballistic movements on data-entry keypads

Abstract

Research to date on movement times on data-entry keypads has assumed that the movements are made under visual control [Drury, C.G., Hoffmann, E.R., 1992. A model for movement times on data-entry keyboards. Ergonomics 35, 129–147; Hoffmann, E.R., Tsang, K.T., Mu, A., 1995. Data-entry keyboard geometry and keying movement times. Ergonomics 38 (5), 940–950; Silfverberg, M., MacKenzie, I.S., Korhonen, P., 2000. Predicting text entry speed on mobile phones. In: Proceedings of the ACM Conference on Human Factors in Computing Systems – CHI 2000. ACM, New York, pp. 9–16]. This is often not the case; where the value of Fitts’ Index of Difficulty is low, it is likely that movements will be made ballistically. A survey of commonly used keypads on devices such as mobile phones and ATMs shows that there is a need to study movement times when these ID values are less than those for which movements are likely to be made under visual control [Gan, K.-C., Hoffmann, E.R., 1988a. Geometrical conditions for ballistic and visually-controlled movements. Ergonomics 31, 829–839]. A series of experiments on simulated and real keypads indicates that the ballistic form of movement is generally valid and may be modelled by a modification of the ballistic movement time model of Hoffmann [1981. An ergonomics approach to predetermined motion time systems. In: Australian Institute of Industrial Engineers, Proceedings, Ninth National Conference, pp. 33–47] and of Gan and Hoffmann [1988a. Geometrical conditions for ballistic and visually-controlled movements. Ergonomics 31, 829–839l; 1988b. Sequential ballistic movement. Ergonomics 31 (10), 1421–1436]. A model is developed for the time to complete sequences of number entries containing up to 5 numbers. In this model, the movement times are related to the square-root of the sum of the movement amplitudes. Relevance to industry Many industrial applications require the use of keypads for data entry. Movements may be made ballistically or visually controlled, depending on the geometry of the keypad. As the time for data entry is dependent on geometry, a model for time taken is necessary for predicting human performance.