Industry research advocates a 4 second rule for web pages to load. Usability engineers note that a response time over 1 second may interrupt a user's flow of thought. There is a general belief that, all other factors equal, users will abandon a slow search engine in favor of a faster alternative. This study compares two mock search engines that differ only in branding (generic color scheme) and latency (fast vs. slow). The fast latency was fixed at 250 ms, while 4 different slow latencies were evaluated: 2s, 3s, 4s, and 5s. When the slower search engine latency is 5 seconds, users state that they perceive the fast engine as faster. When the slower search engine latency is 4 or 5 seconds, users choose to use the fast engine more often. Based on pooling data for 2 s and 3 s, once slow latency exceeds 3 seconds, users are 1.5 times more likely to choose the fast engine.
This work was originally presented at the ASA Quality and Productivity Research Conference in June 2008.