Ecological psychology comprises two fundamental complementary areas of study: perception and action, as introduced by the American psychologist, J. J. Gibson and the Russian physiologist, Nikolai A. Bernstein, respectively. For Gibson perception is the direct pick-up of invariant information by which animals control their actions to reach environmental goals, not the passive registration of elementary sensations from which experiences are (unconsciously), inferred or computed. Where Gibson rejects the computer metaphor in the study of perception, Bernstein rejects the executive metaphor in the study of action. Both views challenge psychology to develop a functionally integrated organism-environment system, governed by laws, in the place of a psychology of internal states or isolatable faculties, governed by rules. Here the smallest unit of analysis is taken to be the perceiving-acting cycle situated in intentional contexts. The historical motivation of ecological psychology is reviewed and critically discussed.