Bivariate pointing movements on large touch screens: Investigating the validity of a refined Fitts' Law Jennifer Bützler * , Sebastian Vetter, Nicole Jochems and Christopher M. Schlick Chair and Institute of Industrial Engineering and Ergonomics of RWTH Aachen University, Germany Abstract. On the basis of three empirical studies Fitts’ Law was refined for bivariate pointing tasks on large touch screens. In the first study different target width parameters were investigated. The second study considered the effect of the motion angle. Based on the results of the two studies a refined model for movement time in human-computer interaction was formulated. A third study, which is described here in detail, concerns the validation of the refined model. For the validation study 20 subjects had to execute a bivariate pointing task on a large touch screen. In the experimental task 250 rectangular target objects were displayed at a randomly chosen position on the screen covering a broad range of ID values (ID= [1.01; 4.88]). Compared to existing refinements of Fitts’ Law, the new model shows highest predictive validity. A promising field of application of the model is the ergonomic design and evaluation of project management software. By using the refined model, software designers can calculate a priori the appropriate angular position and the size of buttons, menus or icons. Keywords: Fitts’ Law, bivariate pointing task, movement time, human factors of software-systems * Corresponding author. E-mail: j.buetzler@iaw.rwth-aachen.de Work 41 (2012) 3526-3532 DOI: 10.3233/WOR-2012-0631-3526 IOS Press 3526 1051-9815/12/$27.50 © 2012 – IOS Press and the authors. All rights reserved