Affordances

An affordance is the possibility of an action on an object or environment.

Though additional meanings have developed, the original definition in psychology includes all actions that are physically possible. When the concept was applied to design, it started also referring to only those action possibilities which one is aware of.

The word is used in a variety of fields: perceptual psychology, cognitive psychology, environmental psychology, industrial design, human–computer interaction (HCI), interaction design, communication studies, instructional design, science, technology and society (STS), and artificial intelligence.

Psychologist James J. Gibson originally introduced the term in his 1977 article "The Theory of Affordances" and explored it more fully in his book The Ecological Approach to Visual Perception in 1979. He defined an affordance as what the environment offers or furnishes the animal. Notably, Gibson compares an affordance with an ecological niche emphasizing the way niches characterize how an animal lives in its environment. An affordance is independent of an individual's ability to recognize it or even take advantage of it, and so, should not be confused with a privately perceived world or a phenomenology of perception. An affordance is relational and characterizes the suitability of the environment to the observer, and so, depends on their capabilities. For instance, a set of steps which rises four feet high does not afford climbing to the crawling infant. Gibson's is the prevalent definition in cognitive psychology.

According to Gibson, humans tend to alter and modify their environment so as to change its affordances to better suit them. On his view, humans change the environment to make it easier to live in (even if making it harder for other animals to live in it): to keep warm, to see at night, to rear children, and to move around. This tendency to change the environment is natural to humans, and Gibson argues that it is a mistake to treat the social world apart from the material world or the tools apart from the natural environment. He points out that manufacturing was originally done by hand as a kind of manipulation.

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