Editing Perception (section)

=== Perception-in-action ===
From Gibson's early work derived an ecological understanding of perception known as ''perception-in-action,'' which argues that perception is a requisite property of animate action. It posits that, without perception, action would be unguided, and without action, perception would serve no purpose. Animate actions require both perception and motion, which can be described as "two sides of the same coin, the coin is action." Gibson works from the assumption that singular entities, which he calls ''invariants,'' already exist in the real world and that all that the perception process does is home in upon them.

The [[Constructive perception|constructivist view]], held by such philosophers as [[Ernst von Glasersfeld]], regards the continual adjustment of perception and action to the external input as precisely what constitutes the "entity," which is therefore far from being invariant.<ref>Consciousness in Action, S. L. Hurley, illustrated, [[Harvard University Press]], 2002, 0674007964, pp. 430–432.</ref> Glasersfeld considers an ''invariant'' as a target to be homed in upon, and a pragmatic necessity to allow an initial measure of understanding to be established prior to the updating that a statement aims to achieve. The invariant does not, and need not, represent an actuality. Glasersfeld describes it as extremely unlikely that what is desired or [[Fear processing in the brain|feared]] by an organism will never suffer change as time goes on. This [[social constructionist]] theory thus allows for a needful evolutionary adjustment.<ref>Glasersfeld, Ernst von (1995), ''Radical Constructivism: A Way of Knowing and Learning,'' London: RoutledgeFalmer; Poerksen, Bernhard (ed.) (2004), ''[https://books.google.com/books?id=8-_EsHHxHYcC The Certainty of Uncertainty: Dialogues Introducing Constructivism],'' Exeter: Imprint Academic; Wright. Edmond (2005). ''Narrative, Perception, Language, and Faith,'' Basingstoke: [[Palgrave Macmillan]].</ref>

A mathematical theory of perception-in-action has been devised and investigated in many forms of controlled movement, and has been described in many different species of organism using the [[General Tau Theory]]. According to this theory, "tau information", or time-to-goal information is the fundamental ''percept'' in perception.