Don Norman's mental models

Their wordsAffordances determine what actions are possible. Signifiers communicate where the action should take place. We need both.

Their wordsAffordances control what actions are possible. For designers, signifiers are far more important. Signifiers are how communication takes place, how one signals the appropriate controls and operations.

Their wordsTwo of the most important characteristics of good design are discoverability and understanding.

Their wordsThe most important principle for taming complexity is to provide a good conceptual model, which has already been well covered in this book.

Their wordsHuman error is blamed for over 90 percent of industrial and automobile accidents. It is the leading cause of aviation accidents, and medical error is reported to be the third-largest cause of death in the entire United States. Horrifying? Yes, but why do we label it “human error”? It is design error.

Their wordsNo matter how brilliant the product, if people cannot use it, it will receive poor reviews. It is up to the designer to provide the appropriate information to make the product understandable and usable.