Human interaction with a computer is often seen in terms of a cycle: think – act – perceive impact on world/system – think – act ... The most influential explicit version of this is Norman's seven-stage model, but it is the implicit backdrop of the majority of discussion in HCI. In principle as a cycle there is no beginning or end but where one thinks of it starting can privilige different positions: with cognitive explanations starting at 'think' and ecological psychology focusing on 'perceive'.
Used in glossary entries: cognitive explanations, ecological psychology, Norman's seven-stage model