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Mental modelEstablished researchIntermediate

Mental Models

Users act on their belief about how the system works, not on how it actually works.

Definition

A mental model is a person's internal representation of how something functions, built from prior experience and from the evidence the interface provides. Norman distinguishes the designer's conceptual model, the system image the product presents, and the user's mental model formed from that image.

Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.

On this page
  1. Definition
  2. The system image is the only channel
  3. Where model mismatches show up
  4. Finding the mismatch
  5. In practice
  6. Sources
  7. Continue from here

The system image is the only channel

Designers cannot transmit their conceptual model directly. Users construct their own model entirely from what the product shows them: its structure, its vocabulary, its feedback and its behaviour. If the system image is unclear, users build a model anyway, and it will be wrong.

Most confusing interfaces are not missing information. They are presenting a system image that implies a different model from the one the system actually implements.

Where model mismatches show up

  • Cloud sync: users believe files are in one place, the system maintains copies with a reconciliation policy, and conflict dialogs are incomprehensible as a result.
  • Permissions: users think in terms of people and things, systems implement roles and inheritance, and the sharing dialog fails to bridge the two.
  • Drafts and publishing: if the interface does not make the two states visibly distinct, users cannot predict who can see what.
  • Undo scope: users expect undo to reverse the last thing they did, systems often scope it per surface, and the mismatch produces data loss.

Finding the mismatch

  1. 1

    Ask users to explain it

    In research, ask 'what do you think happens when you press this' before they press it. The explanation reveals the model.

  2. 2

    Look for the wrong recovery

    When something goes wrong, users act on their model. What they try first tells you what they believe.

  3. 3

    Read the support tickets

    Repeated 'why did it do X' questions map directly to a mismatch.

  4. 4

    Fix the system image, or the system

    Either make the interface express the real model, or change the model to the one users already hold. The second is often cheaper long-term.

In practice

Sync conflict dialogs

File sync

A conflict dialog is a request for the user to resolve something in a model they do not hold. Products that resolve automatically and keep both versions visibly, rather than asking, remove the mismatch instead of documenting it.

Sharing and permissions

Collaboration tools

Interfaces that state the outcome in plain language, such as 'anyone with the link can view', work because they express the result rather than the mechanism.

Sources

Where a source establishes something narrower than the popular reading of it, the note says so.

  • The Design of Everyday Things

    D. A. Norman, Basic Books, 1988, revised 2013

  • Mental Models

    P. N. Johnson-Laird, Harvard University Press, 1983

Continue from here

Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.

Applies when you are designing

An AI Product

Explains

The mechanism underneath these entries.

Applied through

Where this shows up as a concrete interface decision.

Often used with

These usually appear in the same screen or the same decision.

Practical example

A worked decision where this was the deciding factor.

Check your work

Review passes that test whether this was done properly.

Short definition

The one-paragraph version, for when that is all you need.

Related concept

Connected closely enough to change how you apply this.