The Psychology of Speed
We intuitively know that faster is better, but what's the psychology and physiology behind it?
Feeling fast and being fast are different problems. This talk is about the gap between them.
About the talkPermalink to this heading
Performance work starts with a stopwatch, but the number on the stopwatch and the speed a user perceives are not the same quantity. The difference is psychological, it is well studied, and it is largely under your control as a designer.
This talk takes the research on waiting — why an occupied wait feels shorter, why uncertainty hurts more than duration — and maps it onto the concrete decisions you make when building an interface.
What's coveredPermalink to this heading
- What the business data shows. The BBC lost 10% of additional users for every extra second of load time; Pinterest turned a 40% load-time improvement into 15% more SEO traffic and 15% more conversions; the Financial Times saw engagement rise 30%.
- Three rules of waiting. Unoccupied time feels longer than occupied time, anxiety stretches a wait, and an unknown wait feels longest of all.
- Miller's thresholds. Feedback inside 100ms, updates every second, actions completed within three seconds — published in 1968, and still the budget.
- Targets worth holding. Cumulative Layout Shift at 0, First Input Delay between 50 and 100ms, First Contentful Paint at one second, Largest Contentful Paint at three, Time to Interactive at three and a half.
- Designing the wait. Occupy it by showing something early and prioritising content; reduce anxiety with visual stability, optimistic UI and feedback; remove uncertainty by anchoring the user, showing progress and explaining the delay.
- Measuring perception. RUM over synthetic, custom User Timing marks for the moments that matter to you, and full capture rather than a sample.
