The paper challenges the notion that any Fitts' Law model can be applied generally to human-computer interaction, and proposes instead that applying Fitts' Law requires knowledge of the users' sequence of movements, direction of movement, and typical movement amplitudes as well as target sizes. Two experiments examined a text selection task with sequences of controlled movements (point-click and point-drag). For the point-click sequence, a Fitt's Law model that used the diagonal across the text object in the direction of pointing (rather than the horizontal extent of the text object) as the target size provided the best fit for the pointing time data, whereas for the point-drag sequence, a Fitts' Law model that used the vertical size of the text object as the target size gave the best fit. Dragging times were fitted well by Fitts' Law models that used either the vertical or horizontal size of the terminal character in the text object. Additional results of note were that pointing in the point-click sequence was consistently faster than in the point-drag sequence, and that pointing in either sequence was consistently faster than dragging. The discussion centres around the need to define task characteristics before applying Fitts' Law to an interface design or analysis, analyses of pointing and of dragging, and implications for interface design.

Two experiments examined selecting text using a movement sequence of pointing and dragging. Experiment 1 showed that, in the Point-Drag sequence, the pointing time was related to the pointing distance but not to the width of the text to be selected; in contrast, pointing time was related to both the pointing distance and the width of the text in the Point-Click sequence. Experiment 2 demonstrated that both the pointing and dragging times for the Point-Drag sequence were sensitive to the height of the text that was selected. The discussion of the results centers around the application of Fitts' Law to pointing and dragging in a point-drag sequence, proposing that the target for pointing is the leftmost edge of the text to be selected, and the target for dragging is the rightmost edge of the text.