An important function of cognitive affordance is communication, agreement about meaning via words or symbols. Communication is exactly what makes precise wording effective as a cognitive affordance: something to help the user in knowing, for example, what to click on. We see symbols, constraints, and shared conventions as essential underlying mechanisms that make cognitive affordances work, as Norman (1999) says, as “powerful tools for the designer.”

In the tradition of The Design of Everyday Things (Norman, 1990), we illustrate with a simple and ubiquitous non-computer device, a device for opening doors. The hardware store carries both round doorknobs and lever-type door handles. The visual design of both kinds conveys a cognitive affordance, helping users think or know about usage through the implied message their appearance gives to users: “This is what you use to open the door.” The doorknob and lever handle each suggests, in its own way, the grasping and rotating required for operation.