Key takeaways
When a system takes longer than 400 ms to respond to its user, the user’s focus and productivity drop sharply.
Origins
In 1982, Walter J. Doherty and Ahrvind Thadani published research at IBM that put the optimum response time of a computer interaction at 400 milliseconds. Until then, two seconds had been the accepted standard for a “fast” response. They found that when the computer answers a command within 400 milliseconds, with a result or with a “could not be completed”, the interaction falls under the Doherty Threshold, and users rate it as the most productive and the smoothest. Products that respond this quickly also tend to be hard to put down.
Further reading
- The Economic Value of Rapid Response Time — Jim Elliott
- This 70s UX gem still applies today — Michael Gugel | Medium
- Doherty Threshold on Laws of UX — Jon Yablonski
The illustration is our own, drawn after the idea of this law’s card in Laws of UX by Jon Yablonski.
