Prediction of pointing and dragging times in graphical user interfaces

Abstract

An experiment is described which demonstrates that the point-drag sequence common on interactive systems can be modelled as two separate Fitts law tasks — a point-select task followed by a drag-select task. Strong prediction models were built; however, comparisons with previous models were not as close as the standard error coefficients implied. Caution is therefore warranted in follow-up applications of models built in research settings. Additionally, the previous claim that target height is the appropriate substitute for target width in calculating Fitts' index of difficulty in dragging tasks was not supported. The experiment described varied the dragging target's width and height independently. Models using the horizontal width of the drag target or the smaller of the target's width or height outperformed the target height model.