PREDICTION OF POINTING AND DRAGGING TIMES IN GRAPHICAL USER INTERFACES

An experiment is described which demonstrates that the point-drag sequ ence common on interactive systems can be modelled as two separate Fit ts law tasks - a point-select task followed by a drag-select task. Str ong prediction models were built however, comparisons with previous mo dels were not as close as the standard error coefficients implied. Cau tion is therefore warranted in follow-up applications of models built in research settings. Additionally, the previous claim that target hei ght is the appropriate substitute for target width in calculating Fitt s' index of difficulty in dragging tasks was not supported. The experi ment described varied the dragging target's width and height independe ntly. Models using the horizontal width of the drag target or the smal ler of the target's width or height outperformed the target height mod el.