The Design of Everyday Things

Activity-focused design prioritizes usage, in contrast to HCD, which places users at the fore of the design process. Activity-focused design is compatible with HCD and best suited for products destined for large, heterogenous markets, such as automobiles and computers.

Affordances describe the relationship between objects and people, namely, what users believe are possible actions based on the physical properties of the object. Glass, for example, affords transparency and seeing through, but not passage. Some affordances are perceivable, while others are not.

Conceptual models are simplified (and not necessarily accurate) explanations of how things work. Conceptual models are often built on fragmentary information. However, good conceptual models allow users to predict the effects of their actions, even with simplified, incomplete information.