Affordance: How Environments Offer Possibilities for Action

An affordance is a possibility for action that an environment offers to an agent. A firm, level surface may afford walking, and a cup handle may afford grasping, but a high step does not offer the same possibilities to an adult, a toddler and a person with limited mobility. An affordance is neither a fixed “function” possessed by an object alone nor merely a subjective idea. It arises from the relation between environmental properties and an agent’s capacities.

Psychologist James J. Gibson developed the concept systematically. Its importance lies in the thought that perception often does not begin with a neutral shape followed by an inference about use. We may directly see something as sittable, crossable or to be avoided. Buttons, door handles and piano keys likewise indicate possible actions. A clear indication, however, does not guarantee that an action is correct or will occur.

Affordance also differs from possibility in general. Many actions are theoretically possible; an affordance concerns what can actually be done under particular bodily, practical and environmental constraints. It shifts the question from “What is this thing?” to “What does this relationship allow someone to do now?”

https://www.routledge.com/The-Ecological-Approach-to-Visual-Perception-Classic-Edition/Gibson/p/book/9781848725782
https://www.interaction-design.org/literature/book/the-encyclopedia-of-human-computer-interaction-2nd-ed/affordances%EF%BB%BF