Mental Models

What are mental models?

Mental models are internal representations used to understand situations and reason about what may happen. The term can refer broadly to a person’s understanding of a system or more specifically to a theory of reasoning about possibilities.

Mental model theory

In Johnson-Laird’s account (2010), people construct representations of possibilities consistent with premises and their knowledge, then reason from them. The theory explains how considering too few possibilities can produce systematic errors, while counterexamples can help reject an invalid conclusion.

A model is not necessarily a conscious diagram or a verbal rule. Nor is every assumption a mental model in the same technical sense. In product design, the useful question is what users expect the system to do and how their actions reveal that expectation.

An example in product design

For example, a driver expects familiar controls when entering a different car. An unfamiliar interface can frustrate an experienced user when it violates those expectations. Designers can test where those expectations help people and where the interface violates them.