The design community has growing familiarity with the concept of affordances and with the utility of this concept in many areas of design. Less emphasis has been placed on natural processes by which people acquire knowledge about affordances. Consequently, little is known about how design might be optimized to enable users to detect the actions that are available in a given human–machine system. We review scientific research about what people do to obtain information about affordances. We discuss implications of this research for design.