Good interface design is largely applied psychology. These five principles are well-established, easy to apply, and each one has a concrete implication for what you build.
Hick's Law: choices cost time
Decision time rises with the number and complexity of options. A settings page with forty toggles is not flexible, it is expensive to use.
Set good defaults and hide advanced options behind progressive disclosure. Most users never change a default, which means your defaults are effectively your product for the majority of your audience.
Miller's Law: working memory is small
People hold only a handful of items in working memory at once. Navigation with fifteen top-level entries exceeds that budget before the user has begun their task.
Group related items and keep any single list short. This is why phone numbers and card numbers are chunked, and the same logic applies to menus, form sections and dashboard tiles.
Jakob's Law: familiarity beats novelty
Users spend the overwhelming majority of their time on other sites, and they arrive expecting your interface to behave like those. A logo in the top left that returns home is not unimaginative, it is correct.
Spend your novelty budget on the part of the product that is genuinely differentiated. Reinventing navigation, form controls or checkout costs comprehension and buys nothing.
- Keep conventional placement for navigation, search and account controls.
- Use standard form controls; custom selects break keyboard and screen reader behaviour.
- Reserve original interaction design for your actual differentiator.
Peak-end rule and the Zeigarnik effect
People judge an experience by its most intense moment and its ending, not its average. A rough middle with an excellent completion state is remembered better than a uniformly mediocre flow. Invest in success states and error recovery.
Separately, unfinished tasks stay mentally active. A visible progress indicator on a multi-step flow measurably improves completion, because an explicit remaining step is a stronger pull than an unbounded one.
Key takeaways
- Defaults are the product for most users; choose them carefully.
- Chunk long lists — working memory runs out fast.
- Follow convention everywhere except your real differentiator.
- Design the ending; it disproportionately shapes the memory.
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