Een kwaliteit van een voorwerp, of een milieu, dat een individu toestaat om een actie uit te voeren. De termijn wordt gebruikt op een verscheidenheid van gebieden: Wahrnehmungspsychologie, cognitieve psychologie, milieu psychologie, industrieel ontwerp, human-computer interactie (HCI), interactie ontwerp en kunstmatige intelligentie.
(Deze beschrijving is op Wikipedia in het Engels te vinden.)
Volgens Don Norman in “The Psychology of Everyday Things” (1988, p. 9):
… the term affordance refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used. […] Affordances provide strong clues to the operations of things. Plates are for pushing. Knobs are for turning. Slots are for inserting things into. Balls are for throwing or bouncing. When affordances are taken advantage of, the user knows what to do just by looking: no picture, label, or instruction needed.
Maar hierop kwam Don Norman later terug door te schrijven dat hij in “The Psychologist of Everyday Things” beter de term “perceived affordance” had kunnen gebruiken.
I introduced the term affordance to design in my book, “The Psychology of Everyday Things” (POET: also published as “The Design of …”). The concept has caught on, but not always with true understanding. Part of the blame lies with me: I should have used the term “perceived affordance,” for in design, we care much more about what the user perceives than what is actually true. What the designer cares about is whether the user perceives that some action is possible (or in the case of perceived non-affordances, not possible).
Vergelijking tussen de definitie van Gibson en Norman:
A situation where an object’s sensory characteristics intuitively imply its functionality and use.
A button, by being slightly raised above an otherwise flat surface, suggests the idea of pushing it. A lever, by being an appropriate size for grasping, suggests pulling it. A blinking red light and buzzer suggests a problem and demands attention. A chair, by its size, its curvature, its balance, and its position, suggests sitting on it.
An affordance is a desirable property of a user interface – software which naturally leads people to take the correct steps to accomplish their goals.
The common psychological term for this is stimulus-response compatibility.