--- title: "Mental Model" url: "https://www.insideuxdesign.com/en/glossar/mental-model" language: "en" description: "What is a mental model? A plain-language guide with an example and tips. Learn how to design products that work the way people expect them to." published: "2026-10-14T09:50:32+02:00" updated: "2026-10-14T13:06:25+02:00" --- # Mental Model A mental model is the idea people form of how something works. It’s based on experience and assumptions, not on how the system actually works under the hood. - **Buchstabe:** M UX glossary # Mental Model A mental model is the idea people form of how something works. It’s based on experience and assumptions, not on how the system actually works under the hood. Imagine someone wants to free up space on their laptop and deletes a few old holiday photos from a synced cloud folder. The assumption behind it: “Gone from the laptop, still safe in the cloud.” A few days later, the photos have vanished from their phone too. Technically, everything worked as designed. The picture in their head just didn’t match what the system actually does. ## Explained simply A mental model is the idea a person forms of how something works. The Nielsen Norman Group describes it, in essence, as what someone believes about a system. The key word is “believes”: mental models aren’t based on facts but on experience, assumptions and habits. They help us predict what will happen when we press a button. Here’s an everyday comparison: many people turn the thermostat all the way up so the room warms up faster. Behind that is the idea that the dial works like a faucet: open it further, get more heat. In reality, a thermostat regulates toward a target temperature. The room usually doesn’t heat up any faster, it just ends up too warm. Researcher Willett Kempton studied this kind of folk theory in 1986. The term goes back to Scottish psychologist Kenneth Craik, who argued in “The Nature of Explanation” (1943) that the mind builds small-scale models of reality to anticipate events. The idea was brought into design mainly by Don Norman in his book [The Design of Everyday Things](https://www.insideuxdesign.com/en/ressourcen/the-design-of-everyday-things), first published in 1988 as “The Psychology of Everyday Things”. ## How models drift apart Norman distinguishes three levels: the model in the design team’s heads, the so-called system image (everything the product visibly shows and how it responds) and the user’s model. Design teams can only “talk” to users through the system image. If it’s misleading, users end up with a different model from the one intended. On top of that, people bring expectations from other products. Jakob Nielsen put this into words as “Jakob’s Law”: users spend most of their time on other websites, so they expect yours to work the same way. You’ll find more principles like this in the [Laws of UX](https://www.insideuxdesign.com/en/ressourcen/laws-of-ux) collection. ## An example Back to the cloud folder. Before, the app only shows a brief “File deleted” message. After the redesign, a notice appears: “This file will be deleted on all your devices. You can restore it from the trash for 30 days.” The system works exactly as before. But the system image now explains what really happens, and users’ mental models adjust. ## In practice - **Observe instead of asking.** Have people think aloud during a [usability test](https://www.insideuxdesign.com/en/glossar/usability-testing). When they say what they expect to happen next, you’re hearing their mental model directly. - **Adapt the product first.** Where possible, the system should match people’s expectations, for example in how the navigation is structured. [Card sorting](https://www.insideuxdesign.com/en/glossar/card-sorting) shows you how people mentally group content. - **Explain where you have to deviate.** When a system works differently than people expect, clear labels and short hints at the right moment help more than a long tutorial. ## Related terms [Affordance](https://www.insideuxdesign.com/en/glossar/affordance), [Information Architecture](https://www.insideuxdesign.com/en/glossar/information-architecture), [Card Sorting](https://www.insideuxdesign.com/en/glossar/card-sorting) ## Sources - [Megan Chan: Mental Models and User Experience Design. Nielsen Norman Group, 2024](https://www.nngroup.com/articles/mental-models/) - [Interaction Design Foundation: Mental Models. The Glossary of Human Computer Interaction](https://ixdf.org/literature/book/the-glossary-of-human-computer-interaction/mental-models) - [Willett Kempton: Two Theories of Home Heat Control. Cognitive Science, 1986](https://gwern.net/doc/science/physics/1986-kempton.pdf) - [Don Norman: The Design of Everyday Things. Revised and expanded edition, Basic Books, 2013](https://www.hachettebookgroup.com/titles/don-norman/the-design-of-everyday-things/9780465050659/) ## More terms [ ### A/B Testing An A/B test is an experiment that shows two versions of a page or element at the same time to randomly split groups of visitors. It lets you decide with real data which version works better. ](https://www.insideuxdesign.com/en/glossar/a-b-testing) [ ### ARIA ARIA is a W3C standard that adds roles, states and properties to HTML. It tells screen readers what an element is and how it currently behaves. ](https://www.insideuxdesign.com/en/glossar/aria) [ ### Accessibility Accessibility means designing websites, apps and digital documents so that everyone can use them, including people with visual, hearing, motor or cognitive disabilities. ](https://www.insideuxdesign.com/en/glossar/accessibility) [ ### Affordance An affordance describes what action an object makes possible and whether people can recognize it: a button invites you to press it, a handle invites you to pull. ](https://www.insideuxdesign.com/en/glossar/affordance) [ ### Alt Text Alt text is a short text version of an image, stored in the HTML alt attribute. Screen readers read it aloud so people who can’t see the image get the same information. ](https://www.insideuxdesign.com/en/glossar/alt-text) [ ### Atomic Design Atomic Design is a method for building user interfaces from small, reusable building blocks, from single elements like buttons all the way up to complete pages. ](https://www.insideuxdesign.com/en/glossar/atomic-design) [ ### BFSG The BFSG, Germany’s Accessibility Strengthening Act, has required many companies since 28 June 2025 to make certain products and digital services, such as online shops, accessible. ](https://www.insideuxdesign.com/en/glossar/bfsg) [ ### Card Sorting Card sorting is a research method in which people sort terms written on cards into groups. It shows you how they mentally organize content, so you can plan navigation that makes sense to them. ](https://www.insideuxdesign.com/en/glossar/card-sorting) [ ### Cognitive Load Cognitive load is the mental effort it takes to understand and use an interface. The less unnecessary thinking a design demands, the easier the actual task becomes. ](https://www.insideuxdesign.com/en/glossar/cognitive-load) [ ### Color Vision Deficiency A color vision deficiency means someone has a harder time telling certain colors apart than most people. The most common type is red-green deficiency. ](https://www.insideuxdesign.com/en/glossar/color-vision-deficiency) [ ### Contextual Inquiry Contextual inquiry is a research method where you observe and interview people in their real work environment. It shows you how they actually get tasks done, not just how they describe it. ](https://www.insideuxdesign.com/en/glossar/contextual-inquiry) [ ### Contrast Ratio The contrast ratio describes how much two colors differ in brightness, such as text and background. WCAG requires at least 4.5:1 for normal text. ](https://www.insideuxdesign.com/en/glossar/contrast-ratio)