Proposal of two-dimensional effective target width in Fitts´ law

This research was designed to develop the definition of effective target width in a two-dimensional pointing task. The idea of effective target width in a one-dimensional pointing task was extended to effective target width in a two-dimensional pointing task using the two-dimensional joint probability density function. The validity of this theoretical definition was empirically verified. In the experiment, the moving direction of the mouse was from lower left to upper right. The approach angle was fixed to 45°. The fit of conventional and new models to the experimental data was compared by means of contribution of the regression line which showed the relationship between the index of difficulty and the mean pointing time. As a result, we could obtain higher values of contribution for the modelling that introduced effective target width than that for the conventional modelling without it. In conclusion, the proposed two-dimensional definition of effective target width may be promising for predicting and modelling pointing time in human-computer interactions