Psychologist James J. Gibson has developed his "Theory of Affordances" based on an ecological approach towards visual perception. In his work "The Theory of Affordances" (originally published in 1979, 1986) he describes the environment as the surfaces that separate substances from medium in which the animal lives. He continues that the environment offers and provides affordances to the animal. The term "affordances" has been first coined by Gibson, himself. An affordance can be described as a possible action which properties of an object allow or suggest for the observer. For example, a bench affords sitting. Affordances are perceived directly and they are relative to the observer. Gibson states that although the needs of observer can change, the affordance of an object does not change. Gibson’s theory is rather different from the conventional perception theories. His theory has received criticism, mainly for being unclear and underestimating the complexity of perception process.