Website Optimization - The Interactive Effects of Website Delay, Breadth, and Familiarity

Website Optimization is announcing it’s new "speed tweak of the week" illustrating how website delay, breadth, and familiarity have interactive effects on user psychology and performance. A significant three-way interaction among all three factors showed that the ill effects of delay can be dampened by familiarity and breadth. Developers are urged to consider site familiarity, breadth, and delay together rather than separately.

The negative effects of website delay are well known. Faster is better (Schneiderman 1984, Bouch, Kurchinsky, and Bhatti 2000, Galletta et al. 2004). The trade-off between breadth and depth in menu design has been studied extensively. Wider is better (Jacko et al. 1995, Zaphiris and Mtei 1997, Larson and Czerwinski 1998). User familiarity with terminology and structure in website design has also been studied. Familiar is better (Edwards and Hardman 1989). However, the interaction between all three factors has not been studied until recently. Dennis Galletta, Raymond Henry, Scott McCoy, and Peter Polak analyzed how familiarity and breadth dampen the ill effects of website delay by increasing the "scent" of the target page (Galletta et al. 2006). This article summarizes their results.

The Cost of Information Foraging

Information foraging theory holds that humans alter their strategies and structure their environment to maximize their rate of gaining valuable information per unit cost, given the constraints of our environment (Pirolli and Card 1999). Costs include resource costs (calories, money, time, etc.) and opportunity costs (Hames 1992). or the benefits that could be gained by engaging in other activities. Constraints include the profitability of target information sources and the cost of accessing them. As we navigate hypertext structures, we are constantly reevaluating the cost of finding that next tasty morsel of information in an effort to optimize our intake of useful and valuable information (Katz and Byrne 2003).

Information Scent and Natural Selection

Website structure is made up of links, site hierarchy, and the nodes that must be accessed to find information. At each node we make a decision, evaluating the cost and probability of reaching our target. Studies have shown that we prefer low-cost strategies that maximize our hit rates (Todd and Benbasat 1999). We use "information scent" to evaluate this path-following effort by using "proximal cues" like hypertext links and bibliographic citations. Paths with a strong "scent" give users a better idea where they are going ("distal" content) and the promise of speedy delivery (Chi et al. 2000). The theory goes that users will prefer sites offering low-cost information access in terms of time and cognitive effort over high-cost sites. Over time, with the process of natural selection, sites that are slow and difficult to navigate will either evolve to improve returns on information foraging, or be abandoned for lower cost alternatives.

"The basic hypothesis of Information Foraging Theory is that, when feasible, natural information systems evolve towards stable states that maximize gains of valuable information per unit cost." (Pirolli and Card 1999)

The scent is made up of link text, images, layout, and other clues. If the scent of a site is too low, users tend to become lost in a random walk through hyperspace, and may jump to another "patch" of information. If the scent is strong enough, users can easily find their target information and will avoid the wrong paths. We look for these digital tea leaves (read "proximal cues") in a site's structure.

"Information scent is the (imperfect) perception of the value, cost, or access path of information sources obtained from proximal cues, such as bibliographic citations, WWW links, or icons representing the sources." (Pirolli and Card 1999)

Users report "site size, unfamiliar material, predictability of link destinations, unfamiliar terminology, and hierarchical structure" as reasons for becoming lost. These reasons roughly fall into two dimensions, site depth and lack of familiarity, the two factors studied in this article along with website delay.

For the full “The Interactive Effects of Website Delay, Breadth, and Familiarity” article, see http://www.websiteoptimization.com/speed/tweak/scent/

Web Site Optimization
http://www.websiteoptimization.com

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