Conceptual Models and Mental Models
Conceptual model: a (usually highly simplified) explanation of how something works. It need not be complete or even accurate — only useful. Example: files/folders on a computer (there are no real folders inside).
Mental model: the conceptual model as it actually resides in the user's mind. People may hold different models of the same thing; one person may hold several, even conflicting, models.
Key claims:
- A good conceptual model lets people predict the effects of their actions and figure out what to do when things go wrong. Without one, people operate "by rote, blindly."
- Models are usually inferred from the device itself (its perceived structure: signifiers, affordances, constraints, mappings) — so the design must project the right model.
- Simplified models are valuable only while their supporting assumptions hold (e.g., cloud document model breaks when the network drops).
- A false model causes frustration: the two-control refrigerator suggests independent compartments but actually has one thermostat + an airflow valve.
- Conceptual models are a kind of story — humans are predisposed to find causes/explanations (ch.2 "People as Storytellers"), and will postulate mechanisms even where none exist ("folk theories," e.g., the thermostat-as-valve belief).
Communicated via the system image
Designers can't talk to users directly, so the model must be conveyed entirely through the The System Image. Good communication is the key to good conceptual models; good models are the key to understandable products.
Confidence
1.0 — central, explicitly defined.
Sources: ["DOET ch.1 'Conceptual Models' p.25-31; ch.2 'People as Storytellers'"]