The Design of Everyday Things
The conceptual foundation of the field: affordances, signifiers, mapping, feedback, constraints, mental models, and human error as design failure.
Core ideas
Two gulfs. Users must bridge the gulf of execution (what can I do?) and the gulf of evaluation (what happened?). Almost every usability problem is one of the two gulfs left unbridged.
Affordances vs signifiers. What’s possible vs what communicates the possibility. The revised edition introduced ‘signifier’ specifically because designers kept using ‘affordance’ for the visual cue.
Natural mapping, feedback, constraints. Controls arranged like their effects need no manual; every action needs a response; the best error prevention makes wrong actions impossible.
Human error is design error. Slips (right intention, wrong execution) and mistakes (wrong intention) have different fixes — but both are the system’s responsibility. ‘User error’ is a design confession.
Conceptual models. People act on the model the design projects. If the projected model contradicts reality, users will be systematically, confidently wrong.
Use together with
Foundations track lessons 1–3; the affordance/signifier distinction is a standing quiz question because it is the field’s most reliable confusion.