Affordance

The handles on a tea set provide an obvious affordance for holding.

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.

As action possibilities

Psychologist James J. Gibson originally introduced the term in his 1977 article "The Theory of Affordances"[1] and explored it more fully in his book The Ecological Approach to Visual Perception[2] 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.

Gibson argues that learning to perceive an affordance is an essential part of socialization. The theory of affordances introduces a "value-rich ecological object".[2] Affordances cannot be described within the value-neutral language of physics, but rather introduces notions of benefits and injuries to someone. An affordance captures this beneficial/injurious aspect of objects and relates them to the animal for whom they are well/ill-suited. During childhood development, a child learns to perceive not only the affordances for the self, but also how those same objects furnish similar affordances to another. A child can be introduced to the conventional meaning of an object by manipulating which objects command attention and demonstrating how to use the object through performing its central function[3] By learning how to use an artifact, a child “enters into the shared practices of society” as when they learn to use a toilet or brush their teeth.[3] And so, by learning the affordances, or conventional meaning of an artifact, children learn the artifact's social world and further, become a member of that world.

Affordances were further studied by Eleanor J. Gibson, wife of James J. Gibson, who created her theory of perceptual learning around this concept. Eleanor Gibson's book, An Ecological Approach to Perceptual Learning and Development explores affordances further.

Jakob von Uexküll had already discussed the concept in the early twentieth century,[4] calling it the "functional tinting" (funktionale Tönung) of organisms with respect to stimuli.[5]

As perceived action possibilities

In 1988, Donald Norman appropriated the term affordances in the context of human–machine interaction to refer to just those action possibilities that are readily perceivable by an actor. Through his book The Design of Everyday Things,[6] this interpretation was popularized within the fields of HCI and interaction design. It makes the concept dependent not only on the physical capabilities of an actor, but also on their goals, beliefs, and past experiences. If an actor steps into a room containing an armchair and a softball, Gibson's original definition of affordances allows that the actor may throw the chair and sit on the ball, because this is objectively possible. Norman's definition of (perceived) affordances captures the likelihood that the actor will sit on the armchair and throw the softball. Effectively, Norman's affordances "suggest" how an object may be interacted with. For example, the size, shape and weight of a softball make it perfect for throwing by humans, and it matches their past experience with similar objects. The focus on perceived affordances is much more pertinent to practical design problems , which may explain its widespread adoption.

Norman later explained that this restriction of the term's meaning had been unintended, and that he would replace it by "perceived affordance" in any future revision of the book.[7][8] However, the definition from his book has been widely adopted in HCI and interaction design, and both meanings are now commonly used in these fields.

Following Norman's adaptation of the concept, affordance has seen a further shift in meaning where it is used as an uncountable noun, referring to the easy discoverability of an object or system's action possibilities, as in "this button has good affordance".[9] This in turn has given rise to a use of the verb afford – from which Gibson's original term was derived – that is not consistent with its dictionary definition (to provide or make available): designers and those in the field of HCI often use afford as meaning "to suggest" or "to invite".[10]

The different interpretations of affordances, although closely related, can be a source of confusion in writing and conversation if the intended meaning is not made explicit and if the word is not used consistently. Even authoritative textbooks can be inconsistent in their use of the term.[9][10]

When affordances are used to describe information and communications technology (ICT) an analogy is created with everyday objects with their attendant features and functions [11] Yet, ICTs’ features and functions derive from the product classifications of its developers and designers. This approach emphasizes an artifact’s convention to be wholly located in how it was designed to be used.[11] In contrast, affordance theory draws attention to the fit of the technology to the activity of the user and so lends itself to studying how ICTs may be appropriated by users or even, misused.[11]

False affordances

William Gaver[12] divided affordances into three categories: perceptible, hidden, and false.

This means that, when affordances are perceptible, they offer a direct link between perception and action, and, when affordances are hidden or false, they can lead to mistakes and misunderstandings.

See also

References

  1. ↑ James J. Gibson (1977), The Theory of Affordances. In Perceiving, Acting, and Knowing, edited by Robert Shaw and John Bransford, ISBN 0-470-99014-7.
  2. 1 2 James J. Gibson (1979), The Ecological Approach to Visual Perception, ISBN 0-89859-959-8.
  3. 1 2 Emma Williams and Alan Costall (2000), Taking Things More Seriously: Psychological Theories of Autism and the Material-Social Divide, ISBN 0-415-16704-3.
  4. ↑ Uexküll, Jakob von (1980 [1920 etc.]), Kompositionslehre der Natur, edited by Thure von Uexküll, Frankfurt am Main.
  5. ↑ Dorion Sagan (2010). "Introduction: Umwelt after Uexküll". In Jakob von Uexküll; Marina von Uexküll; Joseph D. O'Neil. A Foray Into the Worlds of Animals and Humans: With a Theory of Meaning (Joseph D O'Neil translation of 1940 ed.). University of Minnesota Press. p. 5. ISBN 9781452903798. Organisms in their life-worlds recognize not only sensory inputs, but also functional tones, the use they need to make of certain stimuli if they are to do what they need to survive.
  6. ↑ Donald Norman, The Design of Everyday Things, ISBN 0-465-06710-7. Originally published under the title The Psychology of Everyday Things, often abbreviated to POET.
  7. ↑ Donald A. Norman (1999). Affordance, Conventions and Design. Interactions 6(3):38-43, May 1999, ACM Press.
  8. ↑ Affordance, Conventions and Design (Part 2)
  9. 1 2 Human–Computer Interaction, Preece et al. (1994, p. 6): The authors explicitly define perceived affordances as being a subset of all affordances, but another meaning is used later in the same paragraph by talking about "good affordance."
  10. 1 2 Universal Principles of Design, Lidwell, Holden & Butler (2003, p. 20): The authors first explain that round wheels are better suited for rolling than square ones and therefore better afford (i.e. allow) rolling, but later state that a door handle "affords" (i.e. suggests) pulling, but not pushing.
  11. 1 2 3 Faraj, S., & Azad, B. (2012). The Materiality of Technology: an Affordance Perspective. In Materiality and Organizing: Social Interaction in a Technological World. ISBN 9780199664054.
  12. ↑ Gaver, William W. (1991). "Technology affordances". Proceedings of the SIGCHI conference on Human factors in computing systems Reaching through technology - CHI '91. p. 79. ISBN 0897913833. doi:10.1145/108844.108856.
  13. ↑ "Affordances"
  14. ↑ "Placebo buttons, false affordances and habit-forming"

Additional reading

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