The Theory of Affordances - James Gibson
Affordance is a combination of physical properties if the environment that is uniquely suited to a given animal - to his nutritive system or acting system.
Affordance is neither subjective nor objective, and in fact more easily perceived bu an animal (including human), than the properties in isolation. Gibson reasoned about spaces and surfaces, but his theory is nonetheless extensible to auditory perceptions. e.g. A surface is stand-on-able or walk-on-able.
… Thus it may also be walk-on-able if there is optical information for the four properties listed, rigidity, levelness, flatness, and extendedness then the affordance can be perceived if the information is detected. Gibson also argues that the behavior of an observer depends on his Perception of the environment, given the Information from the environment.
Human changes the environment to change what the environment affords him, i.e. making more available what benefits him and less pressing what injures him. (Jay: well was that not the purpose of Urban Planning?)
Objects have qualities of properties (e.g. color, shape), but what human perceive(Perception) (when we look / hear them) are affordances instead of qualities.
Gibson also raised an example with infants, they do not begin by first discriminating qualities of objects but the affordances of objects.
Applications and potentials of affordance
A true affordance of suppoer went unexploited because a false negative affordance of falling opposed it. In the second a negative affordance of collision went unoticed and a positive affordance of exiting was mistakenly registered.