Designers use the word 'affordance' in a way its inventor never meant.
The psychologist James Gibson coined 'affordance' for what the environment offers an animal: a step affords climbing to an adult, but not to a crawling baby. Don Norman borrowed it for design in 1988 to mean what users can see they can do. The shift caused so much confusion that Norman later introduced a new word.
James J. Gibson introduced the term in 1966 and set out his best-known definition in 1979: the affordances of the environment are what it offers the animal, what it provides or furnishes, for good or ill. The key idea is that affordances are relational. A one-metre step does not afford climbing to an infant, but may offer an adult a seat or a way upstairs. What something affords depends on the body, abilities and needs of whoever is looking.
In 1988 the usability researcher Donald Norman adapted the term for human-computer interaction to mean action possibilities that a person can readily perceive, and his book The Design of Everyday Things made that meaning famous. In Gibson's sense, you could throw an armchair and sit on a softball, since both are physically possible. In Norman's sense, the chair invites sitting and the ball invites throwing. His version spread rapidly through interaction design, and designers began saying a button 'has good affordance' or that a design 'affords' tapping, meaning suggests or invites.
Norman later said the narrowing was unintended. With touchscreens, designers needed to show where actions were possible on flat glass that has no physical handles, and they reached for 'affordance'. In his 2013 revision he offered 'signifiers' instead: affordances determine what actions are possible, while signifiers communicate where the action should take place. Both meanings are still in use, and textbooks are not always consistent.
Other researchers have refined the idea further. William Gaver distinguished perceptible affordances, hidden ones, like using a shoe to help push a cork out of a wine bottle, and false ones, such as a placebo button that looks usable but does nothing. Getting these right is much of what makes an object feel intuitive.
Source: Wikipedia — Affordance · Text summarised from Wikipedia (CC BY-SA 4.0)
