Cool stuff and UX resources

< Back to newsletters

An update on breadth vs. depth

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 too shallow.

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.

Good scent and moderation in everything

Close review of Snowberry et. al. suggests that an alternative explanation for participants' success with a shallow design may be that the category labels were discrete enough to support reliable decision making. It seems that users conceptually manage broader category sets when the names of the elements within the set are discrete and easy to compare. Clear category names provide road signs or 'scent' cues about what lurks behind the link. Good 'scent,' in turn, supports successful category selection. Larson and Czerwinski (1998) tested the hypothesis that there is an interaction between structure, scent and category soundness by measuring speed, click-stream accuracy and perceived 'lostness' while varying breadth/depth parameters of presentation in a well defined information space. They observed that the distinctness of category names was particularly helpful at the highest levels of the information hierarchy, since selecting an incorrect path at the first hierarchical level often resulted in multiple-click backtracks. Note, however, that even with clear and distinct category labels, Larson, et. al. concluded that moderate breadth affords optimal user performance.

The claim that moderate depth supports optimized performance is further buttressed by Zaphiris (2001) computational models of user performance in menu search. Using behavioral values from previous HCI studies, Zaphiris' model predicts that menu design on either extreme (very deep or very broad) will undermine learnability and usability for users. This is postulated to be particularly so for older individuals — the fastest growing segment of Internet users.

Initial and final selection menus should be broadest

An additional parameter of site structure design that is currently drawing more attention is site shape. Consensus is that the initial age should balance breadth with layout/white space to offer a moderate selection of navigational options. Work on the optimal shape of a hierarchical site suggests that concave designs are optimal. A concave shape presents a broad initial selection screen, followed by category decisions over small categories and then followed with a terminal option set that is again somewhat broad. Norman and Chin (1988), and more recently Bernard (2002), demonstrate that for browse-oriented tasks, concave designs take users less time to navigate, and evoke less wasted clicks. In contrast, they observed no differences in ability to successfully navigate the various menu structures for explicit, target-specific scenarios.

What now?

Research comparing navigation efficiency through sites of varying depths and breadths broadly converges on the findings that users find roughly 16 (ungrouped) top-level links leading into 2-3 subsequent menus the most efficient, learnable and least error prone. This knowledge is well and good, but what does that really mean for designers? Today? Now?

First, we can derive some broad (and largely intuitive) design guidelines from this work:

  • Too deep is too deep: users have a more difficult time encoding, and consequently navigating, deep sites.
  • Too broad is too broad: conversely extremely broad sites (which may encourage satisficing) also present a challenge to efficient navigation.
  • Effective sub-grouping reduces perceived breadth: grouping navigation elements thematically improves performance for even the broadest structures.
  • Clear labels improve navigation accuracy: creating clear and distinct labels for navigation elements enhances performance.

More interestingly, careful consideration of the specific tasks used in these studies suggest that the breadth/depth findings map directly to effective Intranet design. Consider the typical participant's task in these studies: find an explicitly named target (search navigation) or navigate to an implicit, user-selected token within a specified category (browse navigation). Since Internet users frequently come to the Web looking for information about a concept, but without a specific page in mind, it is commendable that researchers have begun to focus more extensively on browse-driven exploration. However, it also must be noted that both implicit and explicit search tasks are still essentially serial tasks. That is, the research participants in these studies completed well-defined, single tasks, returning to the home page before initiating the subsequent task. This approach maps directly to the serial task completion behavior patterns observed for the frequently executed Intranet tasks: find a phone number; download a form; check the stock price; change personal benefits information, find a policy.

Thus, the breadth/depth research speaks directly to optimal structure for Intranet design. Further, the cumulative findings of the research challenges the widely implemented approach that Intranets should focus corporate or institutional news wrapped in what is typically a tab-based (or tab plus left side navigation) functional navigation design. Instead, this research suggests that moderately broad site structures, consisting essentially of functionally grouped, transparently labeled link lists will provide the most effective navigation structure with the best perceived usability on Intranets. Anecdotal user-centered field analysis and prototype validation provides additional support for this approach to Intranet design.

Designers who want to know how to take advantage of the depth/breadth research need to think about the kinds of tasks that people do on their sites, and how people approach doing those tasks. Do users tend to do one task at a time? Do they finish that task before they start another? (Intranets are one example of a site type where this serial task completion model holds.) If so, then the task approach on your site is parallel to the task flow that was tested in the depth/breadth work. Therefore, these results apply and a broad, shallow menu architecture should provide users the most efficient and learnable access to resources on your site. In this case, however, the specific type of site is less important. In applying these results it is more important to think about what people do, and how they do it on your site.


References

Bernard, M.L. (2002) Examining the effects of hypertext shape on User Performance. Usability News, 4.2. Original paper

Jacko, J.A. and Slavendy, G. (1996). Hierarchical Menu Design: breadth, depth and task complexity. Perceptual and Motor skills, 82, 1187-1201.

Kiger, J.I., (1984). The depth/breadth tradeoff in the design of menu-driven interfaces. International Journal of Man-Machine Studies, 20, 201-213.

Larson, K and Czerwinski (1998). Web page design: Implications of memory, structure and scent from information retrieval. Proceedings of the Association for Computing Machinery's Computer Human Interaction Conference, 18-23.

Norman, K. L. and Chin, J. P. (1988). The effect of tree structure on search performance in a hierarchical menu selection system. Behaviour and Information Technology, 7, 51-65.

Snowberry, K. Parkinson, S. and Sisson, N. (1983). Computer Display Menus. Ergonomics, 26, 699-712.

Zaphiris, P. (2001). Age Differences and the Depth-Breadth Tradeoff in Hierarchical Online Information Systems. In C. Stephanidis (Ed.), Universal Access in HCI. Mahwah, NJ: Lawrence Erlbaum.

Zaphiris, P. and Mtei, l. (1997). Depth v. Breadth in the Arrangement of Web Links. Original paper

Message from the CEO, Dr. Eric Schaffer — The Pragmatic Ergonomist

Leave a comment here

Subscribe

Sign up to get our Newsletter delivered straight to your inbox

Follow us

Privacy policy

Reviewed: 18 Mar 2014

This Privacy Policy governs the manner in which Human Factors International, Inc., an Iowa corporation (“HFI”) collects, uses, maintains and discloses information collected from users (each, a “User”) of its humanfactors.com website and any derivative or affiliated websites on which this Privacy Policy is posted (collectively, the “Website”). HFI reserves the right, at its discretion, to change, modify, add or remove portions of this Privacy Policy at any time by posting such changes to this page. You understand that you have the affirmative obligation to check this Privacy Policy periodically for changes, and you hereby agree to periodically review this Privacy Policy for such changes. The continued use of the Website following the posting of changes to this Privacy Policy constitutes an acceptance of those changes.

Cookies

HFI may use “cookies” or “web beacons” to track how Users use the Website. A cookie is a piece of software that a web server can store on Users’ PCs and use to identify Users should they visit the Website again. Users may adjust their web browser software if they do not wish to accept cookies. To withdraw your consent after accepting a cookie, delete the cookie from your computer.

Privacy

HFI believes that every User should know how it utilizes the information collected from Users. The Website is not directed at children under 13 years of age, and HFI does not knowingly collect personally identifiable information from children under 13 years of age online. Please note that the Website may contain links to other websites. These linked sites may not be operated or controlled by HFI. HFI is not responsible for the privacy practices of these or any other websites, and you access these websites entirely at your own risk. HFI recommends that you review the privacy practices of any other websites that you choose to visit.

HFI is based, and this website is hosted, in the United States of America. If User is from the European Union or other regions of the world with laws governing data collection and use that may differ from U.S. law and User is registering an account on the Website, visiting the Website, purchasing products or services from HFI or the Website, or otherwise using the Website, please note that any personally identifiable information that User provides to HFI will be transferred to the United States. Any such personally identifiable information provided will be processed and stored in the United States by HFI or a service provider acting on its behalf. By providing your personally identifiable information, User hereby specifically and expressly consents to such transfer and processing and the uses and disclosures set forth herein.

In the course of its business, HFI may perform expert reviews, usability testing, and other consulting work where personal privacy is a concern. HFI believes in the importance of protecting personal information, and may use measures to provide this protection, including, but not limited to, using consent forms for participants or “dummy” test data.

The Information HFI Collects

Users browsing the Website without registering an account or affirmatively providing personally identifiable information to HFI do so anonymously. Otherwise, HFI may collect personally identifiable information from Users in a variety of ways. Personally identifiable information may include, without limitation, (i)contact data (such as a User’s name, mailing and e-mail addresses, and phone number); (ii)demographic data (such as a User’s zip code, age and income); (iii) financial information collected to process purchases made from HFI via the Website or otherwise (such as credit card, debit card or other payment information); (iv) other information requested during the account registration process; and (v) other information requested by our service vendors in order to provide their services. If a User communicates with HFI by e-mail or otherwise, posts messages to any forums, completes online forms, surveys or entries or otherwise interacts with or uses the features on the Website, any information provided in such communications may be collected by HFI. HFI may also collect information about how Users use the Website, for example, by tracking the number of unique views received by the pages of the Website, or the domains and IP addresses from which Users originate. While not all of the information that HFI collects from Users is personally identifiable, it may be associated with personally identifiable information that Users provide HFI through the Website or otherwise. HFI may provide ways that the User can opt out of receiving certain information from HFI. If the User opts out of certain services, User information may still be collected for those services to which the User elects to subscribe. For those elected services, this Privacy Policy will apply.

How HFI Uses Information

HFI may use personally identifiable information collected through the Website for the specific purposes for which the information was collected, to process purchases and sales of products or services offered via the Website if any, to contact Users regarding products and services offered by HFI, its parent, subsidiary and other related companies in order to otherwise to enhance Users’ experience with HFI. HFI may also use information collected through the Website for research regarding the effectiveness of the Website and the business planning, marketing, advertising and sales efforts of HFI. HFI does not sell any User information under any circumstances.

Disclosure of Information

HFI may disclose personally identifiable information collected from Users to its parent, subsidiary and other related companies to use the information for the purposes outlined above, as necessary to provide the services offered by HFI and to provide the Website itself, and for the specific purposes for which the information was collected. HFI may disclose personally identifiable information at the request of law enforcement or governmental agencies or in response to subpoenas, court orders or other legal process, to establish, protect or exercise HFI’s legal or other rights or to defend against a legal claim or as otherwise required or allowed by law. HFI may disclose personally identifiable information in order to protect the rights, property or safety of a User or any other person. HFI may disclose personally identifiable information to investigate or prevent a violation by User of any contractual or other relationship with HFI or the perpetration of any illegal or harmful activity. HFI may also disclose aggregate, anonymous data based on information collected from Users to investors and potential partners. Finally, HFI may disclose or transfer personally identifiable information collected from Users in connection with or in contemplation of a sale of its assets or business or a merger, consolidation or other reorganization of its business.

Personal Information as Provided by User

If a User includes such User’s personally identifiable information as part of the User posting to the Website, such information may be made available to any parties using the Website. HFI does not edit or otherwise remove such information from User information before it is posted on the Website. If a User does not wish to have such User’s personally identifiable information made available in this manner, such User must remove any such information before posting. HFI is not liable for any damages caused or incurred due to personally identifiable information made available in the foregoing manners. For example, a User posts on an HFI-administered forum would be considered Personal Information as provided by User and subject to the terms of this section.

Security of Information

Information about Users that is maintained on HFI’s systems or those of its service providers is protected using industry standard security measures. However, no security measures are perfect or impenetrable, and HFI cannot guarantee that the information submitted to, maintained on or transmitted from its systems will be completely secure. HFI is not responsible for the circumvention of any privacy settings or security measures relating to the Website by any Users or third parties.

Correcting, Updating, Accessing or Removing Personal Information

If a User’s personally identifiable information changes, or if a User no longer desires to receive non-account specific information from HFI, HFI will endeavor to provide a way to correct, update and/or remove that User’s previously-provided personal data. This can be done by emailing a request to HFI at hfi@humanfactors.com. Additionally, you may request access to the personally identifiable information as collected by HFI by sending a request to HFI as set forth above. Please note that in certain circumstances, HFI may not be able to completely remove a User’s information from its systems. For example, HFI may retain a User’s personal information for legitimate business purposes, if it may be necessary to prevent fraud or future abuse, for account recovery purposes, if required by law or as retained in HFI’s data backup systems or cached or archived pages. All retained personally identifiable information will continue to be subject to the terms of the Privacy Policy to which the User has previously agreed.

Contacting HFI

If you have any questions or comments about this Privacy Policy, you may contact HFI via any of the following methods:
Human Factors International, Inc.
PO Box 2020
1680 highway 1, STE 3600
Fairfield IA 52556
hfi@humanfactors.com
(800) 242-4480

Terms and Conditions for Public Training Courses

Reviewed: 18 Mar 2014

Cancellation of Course by HFI

HFI reserves the right to cancel any course up to 14 (fourteen) days prior to the first day of the course. Registrants will be promptly notified and will receive a full refund or be transferred to the equivalent class of their choice within a 12-month period. HFI is not responsible for travel expenses or any costs that may be incurred as a result of cancellations.

Cancellation of Course by Participants (All regions except India)

$100 processing fee if cancelling within two weeks of course start date.

Cancellation / Transfer by Participants (India)

4 Pack + Exam registration: Rs. 10,000 per participant processing fee (to be paid by the participant) if cancelling or transferring the course (4 Pack-CUA/CXA) registration before three weeks from the course start date. No refund or carry forward of the course fees if cancelling or transferring the course registration within three weeks before the course start date.

Individual Modules: Rs. 3,000 per participant ‘per module’ processing fee (to be paid by the participant) if cancelling or transferring the course (any Individual HFI course) registration before three weeks from the course start date. No refund or carry forward of the course fees if cancelling or transferring the course registration within three weeks before the course start date.

Exam: Rs. 3,000 per participant processing fee (to be paid by the participant) if cancelling or transferring the pre agreed CUA/CXA exam date before three weeks from the examination date. No refund or carry forward of the exam fees if requesting/cancelling or transferring the CUA/CXA exam within three weeks before the examination date.

No Recording Permitted

There will be no audio or video recording allowed in class. Students who have any disability that might affect their performance in this class are encouraged to speak with the instructor at the beginning of the class.

Course Materials Copyright

The course and training materials and all other handouts provided by HFI during the course are published, copyrighted works proprietary and owned exclusively by HFI. The course participant does not acquire title nor ownership rights in any of these materials. Further the course participant agrees not to reproduce, modify, and/or convert to electronic format (i.e., softcopy) any of the materials received from or provided by HFI. The materials provided in the class are for the sole use of the class participant. HFI does not provide the materials in electronic format to the participants in public or onsite courses.