# The Psychology of Speed

> We intuitively know that faster is better, but what's the psychology and physiology behind it?

Author: Simon Hearne (https://simonhearne.com/about/)
Published: 2020-10-15
Canonical: https://simonhearne.com/2020/psychology-of-speed/
Tags: WebPerf, video, talk
Video: https://www.youtube.com/watch?v=7i_yQyHdxUo
Slides: https://simonhearne.com/presentations/psych-speed/#/

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Feeling fast and being fast are different problems. This talk is about the gap between them.

## About the talk

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 covered

- **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.