Question

In terms of menu navigation define Breadth and Depth

Answer 1

During the last 5 years a controversy has been brewing concerning the breadth vs. depth in menu design for Web sites. Which is best? A site that is broad and shallow, presenting a lot of choices to the user right away, but only requiring a few layers? Or is it best to have narrow and deep, which means presenting only a few choices at a time, but requiring many layers in? As is usually the case, the answer turns out not to be so simple. In this issue of the newsletter we explore the variables that are emerging as important in the debate.

The history of breadth vs. depth

In the March 1999 issue of this newsletter, Bob Bailey concluded that breadth was better than depth. He reported on two studies that also surveyed past literature and concluded that it was better to have lots of categories in Web menus at the highest level and therefore reduce the number of clicks needed to get to the end point. (Zaphiris and Mtei,1998; Larson and Czerwinski, 1998).

Earlier studies by Snowberry, Parkinson & Sission (1983) demonstrated that in addition to performance and preference declines, navigational error rates increased significantly as hypertext depth increased. This study further demonstrated the value of categorical grouping in shallow structures, showing that participants had an easier time finding resources in a 64 item list that was functionally organized than in a list with random presentation.

Follow-up studies (Kiger, 1984; Jacko & Slavendy 1996; Zaphiris and Mtei 1997) continued to demonstrate that:

• users found resources faster in broader, shallow sites than in narrow deep ones, and
• users understood broader, shallow sites better than they understood narrow deep ones.

However, these studies also began to demonstrate that although shallowness is a unique and defining parameter for success in learning hierarchies, sites can also be tooshallow.

More variables surface

Recent research suggests that there is more to it. When we focus specifically on people browsing the Internet we change the question slightly. Instead of just asking "Which menu structure is best?" we really need to ask, "Which menu structures helps users quickly derive a conceptual model of the site hierarchy?" Creating an accurate representation of the structure and organization of the site results in a more successful and efficient navigation through the resource.

Several factors are thought to influence users' success in learning and traversing information hierarchies. These do include the breadth/depth of hierarchy, but additional critical factors are: the transparency of the category and sub-category labels, qualities of information scent, relative size of categories, and the shape of the hierarchy.