Mental Models

Mental model is an explanation of how something works. The phrase “mental model” is an overarching term for any sort of concept, framework, or worldview that you carry around in your mind.


Mental models are how we understand the world. Not only do they shape what we think and how we understand but they shape the connections and opportunities that we see. Mental models are how we simplify complexity, why we consider some things more relevant than others, and how we reason.

A mental model is simply a representation of how something works. We cannot keep all of the details of the world in our brains, so we use models to simplify the complex into understandable and organizable chunks.

Mental models also guide your perception and behavior. They are the thinking tools that you use to understand life, make decisions, and solve problems. Learning a new mental model gives you a new way to see the world—like Richard Feynman learning a new math technique.


Mental models are one of the most important concepts in human–computer interaction (HCI).

Here, I'll report a few examples from our usability studies. Not coincidentally, using concrete examples often helps people understand abstract concepts (such as "mental models").

Note the two important elements of this definition:

  • A mental model is based on belief, not facts: that is, it's a model of what users know (or think they know) about a system such as your website. Hopefully, users' thinking is closely related to reality because they base their predictions about the system on their mental models and thus plan their future actions based on how that model predicts the appropriate course. It's a prime goal for designers to make the user interface communicate the system's basic nature well enough that users form reasonably accurate (and thus useful) mental models.

  • Individual users each have their own mental model. A mental model is internal to each user's brain, and different users might construct different mental models of the same user interface. Further, one of usability's big dilemmas is the common gap between designers' and users' mental models. Because designers know too much, they form wonderful mental models of their own creations, leading them to believe that each feature is easy to understand. Users' mental models of the UI are likely to be somewhat more deficient, making it more likely for people to make mistakes and find the design much more difficult to use.

Finally, mental models are in flux exactly because they're embedded in a brain rather than fixed in an external medium. Additional experience with the system can obviously change the model, but users might also update their mental models based on stimuli from elsewhere, such as talking to other users or even applying lessons from other systems.

Remember Jakob's Law of the Internet User Experience: Users spend most of their time on websites other than yours. Thus a big part of customers' mental models of your site will be influenced by information gleaned from other sites. People expect websites to act alike.


Mental models are a key concept in the development of instructions, documentation, tutorials, demos, and other forms of user assistance. All such information must be short, while teaching the key concepts that people need to know to make sense of the overall site. It's sometimes worth trying a short comic strip; research has shown that mental-model formation is enhanced when concepts are simultaneously presented in both visual and verbal form.

One of the main reasons thinking aloud method of user testing is that it gives us insights into a user's mental model. When users verbalize what they think, believe, and predict while they use your design, you can piece together much of their mental model.

There are also more advanced knowledge-elicitation methods for gaining deeper insights into mental models, but for most design teams, a few quick think-aloud sessions will suffice. In any case, simple user testing is certainly the first step to take if you suspect that erroneous mental models are costing you business.