People act on what they believe the system will do, not on how it works internally.
A file appears in a folder, so someone expects moving it to change where it lives. If the product treats the folder as a filtered view instead, the same drag has a surprising result. The interface and the person's model disagree.
Origin
Kenneth Craik wrote about internal models in 1943. Don Norman later applied mental models to systems, distinguishing what designers intend, what the interface communicates, and what users come to believe.
Research how people describe the task in their own words. Their categories and predictions reveal the model they are already using.
Make actions and results consistent. If the same operation sometimes moves an item and sometimes copies it, people cannot build a reliable explanation.
Hide technical architecture when it does not help the task. Expose the concepts people need to predict consequences, recovery, and ownership.
When the existing model is wrong, correct it with timely feedback and a clear explanation. Do not let a quiet mismatch keep producing errors.
Digital systems
Files and folders
A folder gives people a familiar way to organize documents. The metaphor works when moving, naming, and deleting behave consistently enough to support accurate predictions.
Physical signals
A thermostat target
A clear target temperature helps people understand that the control sets a destination. Ambiguous markings can make the dial look like a direct heat-output control.
The interface suggests one model while the system follows another, so ordinary actions create surprise, mistrust, or loss of work.
Use clear concepts, consistent behavior, and visible consequences so people can form a useful model and revise it when the system changes.