By the end of this lesson you can
- Explain mental models and why they shape expectations.
- Use familiar patterns so people can rely on what they know.
- Decide when breaking a convention is worth it.
The idea
A mental model is what a person believes about how something works. People build mental models from past experience, especially other products. They expect a logo in the top left to go home, a basket icon to show their basket, and a swipe to dismiss a notification.
Jakob's Law puts it simply: people spend most of their time on other sites, so they expect yours to work the same way.
Patterns
Interaction patterns are proven solutions to common problems: search with suggestions, pull to refresh, tabs, step-by-step checkout. Using them means people can transfer what they know.
When to break conventions
Break a convention only when the benefit is large and tested, and when you can teach the new behaviour quickly. Novelty for its own sake costs learning time and creates errors.
Mismatches
Problems arise when the system model (how it really works) differs from the user's model. For example, people may think "delete" removes a file everywhere when it only removes it from one device. Close the gap with clear labels, feedback and explanation.
Why it matters in real projects
Familiar patterns make products feel easy without effort, and they reduce the need for instructions. Understanding mental models helps you predict confusion before testing and explain it afterwards. It also gives you a strong argument in debates about "creative" but confusing ideas.
A realistic example
A fashion brand's new site hides navigation behind a custom gesture: swiping up on the logo. It wins a design award, but analytics show most visitors never find category pages and conversion drops.
The team returns to a conventional header with visible categories and a search box, keeping brand personality in imagery and typography. Category visits recover within a week.
Step by step
List expectations
For a screen, write what users likely expect from other products.
Check patterns
Compare your design with common patterns for the same task.
Spot deviations
Highlight where you break convention.
Justify or fix
Keep deviations only if clearly better; otherwise use the convention.
Check system vs user model
Find actions where results may surprise people.
Test
Ask people to predict what will happen before they act.
Common mistakes
Mistake Inventing new interactions for common tasks.
Instead Use established patterns.
Mistake Assuming users understand how the system works.
Instead Explain consequences clearly.
Mistake Copying patterns that do not fit the context.
Instead Check the pattern solves your problem.
Check your understanding
Choose an answer, then check it. There is an explanation either way.
Practice exercise
Exercise · about 30 min
Prediction test
Test whether people's mental models match a design.
Steps
- Choose three controls on a screen.
- Ask two people what they think each will do.
- Compare predictions with reality.
- Suggest changes where they differ.
Deliverable
A table of predictions, reality and suggested fixes.
Self-assessment
Tick each item when it is true of your exercise. Be honest; this is for you.
4 items
Summary
- Mental models come from experience.
- Familiar patterns let people transfer knowledge.
- Break conventions rarely and deliberately.
- Close gaps between system and user models.
Further reading
Third-party sources, chosen for reliability. They open in a new tab.
- Mental models (opens in a new tab)Nielsen Norman Group
- Jakob's Law (opens in a new tab)Laws of UX
Your notes
Marking complete updates your course and roadmap progress.