Customer expectations of Web page download times
When writing about Human-Computer Interaction (HCI), I discussed Robert B. Miller's classic research into computer responsiveness and its relevance today to questions of Web site design and site usability. For one response to Miller's findings (by providing more percent-done indicators and busy cursors) see Jakob Nielsen's Web site and his best-selling book, Designing Web Usability.
But Miller's three thresholds are far from the whole story ...
Expectations determine perceptions
Some digging on Google will reveal that in the last 10 years, scientists around the world have investigated the effects of page download time differences on Web users. Why did these researchers , who were usually aware of (and often referenced) the earlier results of Miller and Bickford, feel the need to conduct new studies focused on the Web?
Was it because the Web was reaching a new population with no previous experience of mainframes or hypertext systems? I don't think that explanation is sufficient, because Miller's results were so general they would apply to all computer users, whatever their prior experience.
I believe that researchers can justify doing new studies because they know that people's ultimate experience of, and response to, any computer interaction depends most of all on their prior expectations. As in any area of life, our expectations affect our perceptions.
In his Law of the Internet User Experience, Nielsen pointed out that Users spend most of their time on other sites. In July 2000 he concluded that this fact, together with others, would lead to the End of Web Design -- meaning that Web site designs would converge. Five years later, it is clear that his controversial conclusion has not really come to pass.
While some common idioms and design patterns have emerged, most would agree that site designs still vary widely. In fact, in September 2004 we find Nielsen himself comparing the Web to an anthill built by ants on LSD. In an article about The Need for Web Design Standards, he observes that ...
while users expect 77% of the simpler Web design elements to behave in a certain way, ... confusion reigns for many higher-level design issues.
I believe a key reason for this state of affairs is the presence of what interface design specialist Jared Spool labels design evolution, as sites adapt to observed user behavior. Evolution promotes both diversity, as novel traits emerge to take advantage of environmental niches, and convergence, as less efficient species tend to become extinct. Jared's conclusions about design evolution touch on both aspects:
A small investment in studying how users interact with existing sites can reveal a lot about what works for your users on their tasks. You could easily develop an understanding of the 'best practices' and, from that, produce your own guidelines. [Convergence]
Because you will generate your guidelines by directly observing your users, these guidelines are far more likely to be of value than generalized guidelines produced from sites that have little or nothing to do with your work. Evolution has produced these sites and you can identify which have won the 'survival of the fittest' competition. [Diversity]
In nature, the attribute of speed evolves in only one direction, because faster individuals more often capure their prey and escape predators. On the Web, human nature, specifically our impatience, drives up individual site performance. One consequence of Jakob's Law that he did not write about is that users' expectations of site performance must inevitably converge, because they are set by their experience of other sites. As sites get faster, people expect faster sites, and are less tolerant of slower ones.
Experience determines satisfaction
While Miller's findings identified some important (and largely invariant) behavioral thresholds that apply to all human-computer interactions, an individual person's satisfaction with their interaction with a Web site will always be determined by more than those thresholds alone. The key additional ingredient is their prior experience of the Web environment as a whole, which sets their expectations and provides the context in which they can judge subsequent online interactions.
Nielsen's latest candidate for the scrap heap is the old acronym WYSIWIG. So maybe it's OK to recycle it with a new twist: As a Web user, what you suppose is what you got. Or, as John Donne might have adapted his metaphors for today's interconnected world:
No site is an island, entire of itself
Every page is a piece of the Web, a part of the environment