In the late 1970’s, the notion of an affordance was coined by J.J. Gibson to describe the manner in which an individual’s environment plays a part in explaining the possible actions an individual can take. For example, a dog can drink water in a forest cut by a stream in a manner that would be impossible for that dog in a desert. Likewise, a tall tree provides an opportunity for a man to see beyond a nearby hill, an opportunity that fades when the tree is cut down.
An affordance, according to [Chemero 2000], is an “immediate opportunity for behavior” by an organism. To put it another way, affordances are relationships between agents and their environments that have some causal impact on how the agent acts. Moreover, these affordances are part of the way that agents look at the world: when you see a flight of stairs going up, you see a way to climb to a higher floor. For ecological psychologists like Chemero and Gibson, perception is not restricted to sights, sounds, tastes, touches, and smells. Beyond sense perception, agents see the things around them as instruments to be manipulated.
To make things sound more odd to the unacquainted, affordances are neither objective nor subjective relationships. Because an affordance is a relationship between an agent and something else, and the removal of the agent removes the relationship altogether, an affordance is not an objective thing that can be studied in isolation of its subjects. If you take the animals out of a forest, the stream running through it no longer affords the possibility of taking a drink: there can’t be any drinks if there are no drinkers. However, the existence of an affordance does not soley reside in the mind of an agent – it’s not subjective in the sense of a thought or emotion. Regardless of whether you believe that a dog can drink water without a source of water nearby, the dog will still be thirsty.
The odd nature of affordances can be better understood by considering the claim in [Chemero 2001] that affordance descriptions are not predicates – no property is said to inhere in any object in the environment. When we describe a stream as affording the opportunity to take a drink, we can’t merely stop with a formal representation that looks like
(affords-taking-a-drink the-stream that-dog)
Part of the reason is that it’s not just the stream itself as an object that affords drinking for the dog. The edge of the stream, for example, can’t be a five-foot cliff that would frustrate the dog’s efforts. The stream can’t be crawling with crocodiles, nor can it be frozen over. There are lots of features in the environment that together determine whether or not the dog can quench its thirst – the stream is only a convenient target for predication, not an accurate one.
Unsurprisingly, placement matters when it comes to possible activities. Some actions possible in a New Jersey motel are impossible on the surface of the moon. Thus, a principled way of describing affordances is needed that does representational justice to place and environment while avoiding the bog of fanciful what-ifs (heights, crocodiles, and ice).