The Ergonomic Pragmatist Dr. Eric Schaffer, Ph.D., CPE, founder and CEO of HFI offers practical advice. With problem solving tasks, which are more like Web interaction tasks, they found no reliable effect on performance up to a 5-second delay. One reason that acceptable response times are so difficult to determine is that people's expectations for acceptable response times differ from situation to situation.
Users seem willing to wait varying amounts of time for different types of interactions.
The amount of time a user is willing to wait appears to be a function of the perceived complexity of the request. For example, people will wait longer for requests they think are hard or time-consuming for the computer to perform. Paula Selvidge and Barbara Chaparro at Wichita State University, and Gregory Bender at IBM, conducted a study to examine the effect of download delays on user performance. They found that users were less frustrated with the one-second delay, but their task success and efficiency were not affected by either the 30 or 60 second response times. They attempted to identify how long users would wait for pages to load.