Where does affordance collide?

Gibson coined the word for what the environment offers the animal, what it provides or furnishes, for good or ill. The affordance is a property of the animal-environment system taken together, not of the environment alone and not of the animal alone: a surface affords support for an animal of a given size and weight, and the affordance is specified relative to that animal. Gibson insisted it is neither objective nor subjective but cuts across that dichotomy, and that it is perceived directly, picked up from the ambient optic array without inference or mental representation. The affordance exists whether or not the animal perceives it or has any use for it; it is a fact of the environment as much as a fact of behaviour.[1]

Unit

An animal-environment relation

Recovery means

Not applicable, a relation perceived directly

Measured by

Not a measured variable; established by analysis of what surfaces and layouts offer an animal of a given body scale

Norman imported the word into design in 1988 and changed its referent. He first described an affordance as a relationship between an object and an actor, the perceived and actual properties that determine how a thing could possibly be used: a chair affords sitting, a knob affords turning. Designers took the term to mean the action possibilities the user perceives, and Norman, finding it misused, split it in 1999 into real affordances, what the object actually permits, and perceived affordances, what the user believes it permits, and argued that graphical interface design is almost entirely about the perceived kind and about convention, not about the real kind. He later added signifiers for the cues that tell a user where to act, conceding that much of what he had called perceived affordance was really signification. The break with Gibson is the referent: Gibson's affordance exists independent of perception, Norman's design affordance is defined by it.[2][3]

Unit

An object-actor relationship, as perceived by a user

Recovery means

Not applicable

Measured by

Not a scale; assessed by design analysis and usability testing of whether users perceive the intended action

Gaver reworked the concept for interaction in 1991, keeping Gibson's claim that affordances are properties of the world available for perception but treating the relation between an affordance and the information that specifies it as the design variable. He separated perceptible affordances, hidden affordances, and false affordances, where perceptual information suggests an action the object does not support, and described how affordances can be nested in space and sequential in time, so that acting on one reveals the next. Hartson in 2003 partitioned the idea further into cognitive, physical, sensory, and functional affordances, each a different kind of help the design gives the user. This meaning is neither Gibson's pure relation nor Norman's perception-defined property: it is an engineering vocabulary for the layers of a designed artifact's usability.[4][5]

Unit

A designed artifact's action possibilities and the information specifying them

Recovery means

Not applicable

Measured by

Not a scale; catalogued by type, perceptible or hidden or false, and cognitive or physical or sensory or functional, in design analysis

Hutchby brought affordance into the sociology of technology in 2001 to settle a standoff between technological determinism and social constructivism. Against the constructivist claim that a technology's capacities are entirely a matter of the interpretations placed on it, Hutchby argued that artifacts have affordances: functional and relational possibilities and constraints that different technologies offer to different actors, real enough to resist arbitrary reinterpretation yet realized only in use. The affordance here is a property of a technology relative to a class of users, invoked to explain why some things can be done with a given artifact and others cannot. The word carries Gibson's relational logic into a debate about structure and agency, where it argues about what an object permits rather than helping to design one.[6]

Unit

A technology's possibilities and constraints, relative to actors

Recovery means

Not applicable

Measured by

Not measured; invoked analytically to bound what a technology permits its users