400 Milliseconds. That’s apparently the magic amount of time to keep a user’s attention and increase productivity.
Productivity soars when a computer and its users interact at a pace ( < 400ms ) that ensures that neither has to wait on the other.
This is one reason video games are so addictive and hook people quickly because the response time to your next action is under 400 ms.
400 milliseconds, not 2,000 (2 seconds) which had been the previous standard Walter J. Doherty, 1982
Making things simple, keeping things neat and fast will insure a better experience for the user. Don’t make them think
Reference: Laws Of UX