Fitts' Law, Menu Bars & Web Usability

Unearthed an interesting bit of information this week that the menu bar implementation on Mac operating systems is measurably more usable.

This comes about by applying
Fitts' Law (1954), a model of psychomotor movement which predicts that the time required to move to a given object is a function of the target's distance and size. It is particularly useful in Human Computer Interaction (HCI) applications and in the case of the Mac menu bar it identifies that the positioning of the bar on the finite edge (top) of the screen means rapid movement 'North' with the mouse will always mean the user is successful in finding it. By contrast, the windows user bar is only useful in the active window which can be anywhere on the floating screen space, and by implication can be missed unless greater levels of motor accuracy are applied. (Aside: Have Apple forgotten this law in iTunes? a great article by Coda Hale investigates).

I've been trying to think of examples on the web where Fitts' Law could make life easier. It seems to me that applying
Pie Menu systems (see also Pie Menu Central) or nodal navigation could be effective in the place of Linear Menus, however whether this would be offset by the effect of implementing an unfamiliar user interface and the difficulty in having multiple item menus remains to be seen. There is a rumour, by the way, that Windows Vienna will feature a Pie Menu. Evidently, the most obvious application for a web menu is the use of the screen limits - ie. navigation should be either at the extreme left (c.f. Kalbach & Bosenick, 2003) or top of a page to ensure it is more likely to be on a screen-edge limit. However, more subtle applications might be to keep contextual linking prevalent on the site (keep the links close to the content) and ensure target buttons are obvious and large. Common sense, basic stuff maybe but sometimes it's nice to see a bit of tangible scientific research backing it up.

:: Paul M. Fitts (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, volume 47, number 6, June 1954, pp. 381-391. (Reprinted in Journal of Experimental Psychology: General, 121(3):262--269, 1992).

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