Cultural Forms of Understanding: Reinterpreting Affordances in Extended Cognition — Epoche B2
Gibson cannot have affordances be both invariant and ability-relative An objection that has already been answered James Gibson's ecological psychology is regularly met with an objection from cultural variation [1] . A rock formation in the desert, it is said, offers shelter, a landmark and a source of water to someone raised in that landscape, and offers nothing but an obstacle to a visitor. So the perception of what an environment affords depends on inherited practice and learned skill, and Gibson's claim that affordances are directly perceived must be wrong [2] . This objection does not reach him. Gibson holds that perceiving what things afford is learned. His account of perceptual learning, developed with Eleanor Gibson's work on differentiation, is the education of attention: with experience a perceiver becomes attuned to structure that was always available and that she formerly failed to detect. He is equally clear that affordances can be misperceived, which would be impossible if they were self-announcing. A visitor who sees only rock is, in Gibson's terms, an untrained perceiver in the presence of information she has not learned to pick up. This is his position, not a difficulty for it. There is a real difficulty, and this note sets it out. Gibson needs affordances to satisfy two requirements at once: to be properties of the environment that do not vary with the observer, and to be relative to what the animal can do. Where the animal's capacities are fixed by its body the two requirements agree. Where the capacities are acquired by training they come apart, because nothing in the light changes when a person learns a skill. The claim is deniable, and the position that denies it is set out and answered below. What Gibson actually claims The term is introduced in the eighth chapter of The Ecological Approach to Visual Perception : The affordances of the environment are what it offers the animal, what it provides or furnishes, either for good or ill. Gibson adds, with some satisfaction, that the verb to afford is in the dictionary and the noun affordance is not, because he has made it up. The word was coined to name something that is neither an objective physical property nor a subjective value: it refers to the animal and to the environment together. Two claims then do the work of the theory, and they must be kept apart. The first is relativity. What a surface affords depends on the animal. A horizontal, rigid, flat and sufficiently extended surface affords support for a creature of a certain size and weight [3] , and not for one much heavier. The scale is set by the body, which is why William Warren's measurements of stair climbing find a critical riser height at a fixed proportion of leg length [4] : perceivers judge climbability in units of their own bodies. The second is objectivity. Gibson insists that an affordance is not conferred on an object by an observer's need, and does not change when the observer's needs change. The object offers what it does because it is what it is. This is not a stray remark; it is what keeps affordances from collapsing into the perceiver's valuations, and it is what makes them available to be specified by information in the ambient optic array and picked up without inference. The strain Now put a trained skill into the second requirement. A person who has learned to read desert rock, or to use a stick as a reaching tool, has a capacity she formerly lacked. Her body has not changed. And the optic array in front of her—the structure in the light, which is what Gibson's information consists of—is the same array that stands in front of an untrained companion at her shoulder. The theory now faces two ways of going, and each gives something up. Take the first: say the affordance was there all along and the training changed only the pickup. This is consistent, and it is what the education of attention implies. But it over-generates catastrophically. If everything the environment could support for any skill anyone might acquire is an affordance already, then affordances are present equally for the trained and the untrained, and cease to explain why the two behave differently. Gibson introduced them precisely as the meaningful furniture of an animal's niche, the things that account for what it does. A property shared by every perceiver in the vicinity accounts for nothing. Take the second: index the affordance to the ability, so that the trained perceiver's environment affords shelter and the untrained one's does not. Then the affordance changes without any change in the object or in the light, and objectivity in Gibson's sense is gone. Worse for his programme, the affordance can no longer be specified by structure in the array, since the array is common to both perceivers and the affordance is not. That is the dilemma. It is not the cultural objection with which this note began; it is what remains once that objection has been correctly disposed of. Extended cognition relocates the problem It is tempting to answer by appeal to extended cognition, and worth saying why this does not help. The parity principle that Andy Clark and David Chalmers stated in 1998 concerns Otto's notebook [5] : an external resource that plays the functional role a memory would play counts as part of the cognitive system. Claims about culture and skill scaffolding cognition belong to Clark's later work, where the guiding idea is complementarity rather than parity, and cognitive systems are seen as built out of niches constructed by previous generations. Reaching for the 1998 paper to underwrite a claim about inherited practice is reaching for the wrong text. Suppose the later claim granted, and suppose Fred Adams and Ken Aizawa's objection set aside&mdash [6] ;that coupling a process to an external item does not make the item part of the process. The dilemma is untouched. Extension makes the skilled perceiver's capacities include stick, notebook and tradition; those capacities still