about 5 years ago
A fundamental pillar of usability is response-time. To quote some fascinating research from the 1960s by my hero Robert B. Miller.
[Regarding] response to request for next page. [...] Delays of longer than 1 second will seem intrusive on the continuity of thought.
Assume an inquiry of any kind has been made. The user - and his attention - is captive to the terminal until he receives a response. If he is a busy man, captivity of more than 15 seconds, even for information essential to him, may be more than an annoyance and disruption. It can readily become a demoralizer - that is a, reducer of work pace and of motivation to work.
Lawrence Lessig uses a fantastic analogy when he talks about the change congress movement. He argues that the problem the congress is facing is similar to that of an alcoholic. Before you can address any of the enormous amount of social and economical issues the alcholic faces you first have to address the alchohlism. It's not the only problem, but it is the first problem.
Similarly, slow response-time is usabilitie's alcoholism. A slow computer interface is demoralizing no matter how many flashy colors, pretty graphics and next generation workflows it has.
Everyone in today's Web 2.0 ajax filled web applications should know these axioms
Next time your manager asks you for another feature that will slow down your UI (or refuses you time to rectify your slow UI), it is your duty to to point them back at these truths.