| name | dec-ux-laws |
| description | The Laws of UX and cognitive heuristics beyond the common five — Doherty Threshold, Goal-Gradient, Zeigarnik, Peak-End, Serial Position, Von Restorff, Postel's Law, Parkinson's, Pareto, Occam's Razor, Flow, Banner Blindness. Use when justifying a UX decision with a named principle, designing progress/motivation, placing CTAs and nav, or setting response-time targets. |
| tags | ["ux-laws","psychology","cognitive-heuristics","ux","always-on"] |
Laws of UX & Cognitive Heuristics
Named principles to reason about and defend interface decisions.
| Law | Principle |
|---|
| Doherty Threshold | System response under 400ms keeps users in a productive, engaged state. |
| Goal-Gradient Effect | Motivation rises as users near a goal — show progress, pre-fill early steps. |
| Zeigarnik Effect | People remember incomplete tasks better — use progress bars and "unfinished" cues. |
| Peak-End Rule | Users judge an experience by its most intense moment and its ending, not the average. |
| Serial Position Effect | First and last items are best remembered — place key nav at the ends. |
| Von Restorff (Isolation) Effect | The visually different item is the one remembered — use for the primary CTA. |
| Postel's Law (Robustness) | Be liberal in what you accept (forgiving inputs), conservative in what you send. |
| Parkinson's Law | Tasks expand to fill the time allowed — impose deadlines and constraints. |
| Pareto Principle (80/20) | ~80% of effects come from ~20% of causes — optimize the vital few flows. |
| Occam's Razor | Remove elements until breaking point; the simplest solution that works wins. |
| Flow (Csikszentmihalyi) | Match challenge to skill to keep users absorbed and low-friction. |
| Banner Blindness / Selective Attention | Users ignore anything that looks like an ad or is irrelevant to their goal. |
How to apply
- Budget interactions against the Doherty Threshold (<400ms) — past it, show optimistic UI or progress.
- Combine Goal-Gradient + Zeigarnik for onboarding: visible progress + an obviously incomplete step.
- Use Von Restorff for exactly one primary action per view — make it the visual outlier.
- Don't bury the primary CTA in ad-shaped chrome (Banner Blindness).
