International Encyclopedia of Systems and Cybernetics

J.J. GIBSON developed an ecological theory of perception akin to J.von ÜEXKULL's "Bedeutungslehre" (Science of significances) (1934, 1979). He writes, for instance: "Knee-high for a child is not the same as knee-high for an adult, so the affordance is relative to the size of the individual" (1986, p.128).

GIBSON's theory is basically about visual perception ("Ecological optics"), indeed generally the most used and important tool for our observation of the world.

It is based on ecological observation by living beings, principally what these living observers "make" of what they see, how they see what they see and to which uses they put their perceptions (see "affordance": What are the uses of what they see for any of them, on the base of their tacit knowledge).

GIBSON's theory implies:

1) That perception is based on the general conditions proper to this planet: gravitation level, imperceptible curvature, atmospheric density and transparency (compared for ex. with the characteristics of the aquatic medium).

2) That each observer needs to train her/himself in ecologically satisfactory interpretations of her/his perceptions. This is tantamount to PIAGET's ontology of knowledge, to von FOERSTER's 2nd cybernetics and to autopoiesis. Perception is not a response to a stimulus (a mere "brief and discrete application of energy to a sensitive surface") (p.57), but an act of information pick-up. It thus implies the construction of inner rules of interpretation, based for each species (and individual) in its sensorial equipment.

GIBSON's concept seems important for our ways to define and use perceived entities, and our relations to them.