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Affordance is a term used by perceptual psychologists, also used in the fields of cognitive psychology, environmental psychology, and industrial design. The term was first introduced by psychologist James J. Gibson in 1966, then explored more fully in "The Ecological Approach to Visual Perception" (1979).

An affordance is a property of an object, or a feature of the immediate environment, that indicates how that object or feature can be interfaced with. The empty space within an open doorway, for instance, affords movement across that threshold. A couch affords the possibility of sitting down on it.

Gibson originally meant affordance to refer to all "action possibilites" latent in the environment, objectively measureable, and independent of the individual's ability to recognize those possibilities. Further, those action possibilities are dependent on the capabilities of the actor. For instance, a set of steps with risers four feet high does not afford the act of climbing, if the actor is a crawling infant. So affordances must to be measured along with the relevant actors.

In 1988 Donald Norman refined the term to refer to perceived affordance, as opposed to objective affordance. This distinction that makes the concept dependent not only on the physical capabilities of the actor, but his experience, his expectations, his level of attention, his perceptual ability, etc. If an actor steps into a room with a recliner and a softball, Gibson's definition of affordance allows that the actor may toss the recliner and sit on the softball, because that's objectively possible. Norman's definition of affordance captures the likelihood that the actor will sit on the recliner and toss the softball, because characteristics of the recliner and softball self-explain and self-suggest their own uses.

Norman's definition makes the concept of affordance unmeasurable, and therefore out of the realm of science, but much more pertinent to practical design problems.

Perceptual psychologists can ask, "What is it about this object that makes people want to use it this way?" The object must talk to us with some sort of language. If we can understand this language, then industrial designers can make tools that explain their own functions, and even tools that recommend themselves for some uses and discourage other uses.

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Last updated: 09-01-2005 20:21:48
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