Categories form at the level that maximises information gained per unit of cognitive effort.
Rosch's finding: people say "chair" rather than "furniture" or "Windsor chair" because the middle level carries the most information for the least effort. Basic-level categories are where naming settles across languages.
In practice
- A new starter is told "use the standard template", not "the standard corporate quarterly business review template, version 4".
- A doctor says "take it with food" rather than naming a meal, because the middle level is what the patient will actually remember.