Menu Structure and Ordering of Menu Selection: Independent or Interactive Effects?

The breadth/depth trade-off in menu structure refers to advantages and disadvantages of menu breadth (having fewer levels/pages of menu selections with more selections per level) and depth (having more levels/pages with fewer selections per level). Several studies (Snowberry, Parkinson & Sisson, 1983; Landauer & Nachbar, 1985) demonstrate enhanced user performance with increased breadth. However, other studies (Miller, 1981; Kiger, 1984; Tullis, 1985) fail to show an advantage in user performance with increased depth. Complicating the breadth/depth issue is the issue of the ordering of selections within each menu level. Snowberry et al. found superiority of breadth only with consistent ordering of selections within levels. Card (1982) reported that alphabetical ordering of selections is superior to functional ("logical") ordering, which in turn is superior to random ordering. Do users perceive and utilize menu structure independently of ordering, perhaps by first appraising which level must be accessed, then by determining where in that level the goal selection is? Or are structure and ordering interrelated considerations? These hypotheses were tested in an experiment in which menu breadth and ordering were covaried