Speed is a feature. Not a nice-to-have, not a performance metric for engineers, a core element of user experience that directly affects engagement, task completion, and perceived quality. In 1982, Walter J. Doherty and Ahrvind J. Thadani published research at IBM showing that system response times under 400 milliseconds kept users in a state of productive flow, while responses over 400ms caused users to disengage, lose their train of thought, and work less efficiently. The threshold they identified has since become a benchmark for interface responsiveness.
Doherty Threshold
Why sub-400ms response times keep users engaged and productive
A
Designers Academy
19 March 2025 · 4 min read
DesignPrinciples
In brief
The Doherty Threshold, identified by IBM researchers in 1982, states that system response times under 400 milliseconds maintain user productivity and engagement, while longer delays cause disengagement and inefficiency.
