General Tau Theory

Origin
A theory of perceptuomotor control based on the ecological invariant, tau. The theory was developed from work on J.J. Gibson's notion of ecological invariants in the visual flow-field during a perception-in-action event, and subsequently generalised in the late 1990s to a ubiquitous, amodal theory of perceptuomotor control, General Tau Theory.

General tau theory considers the organism acting as a unified whole in dynamic relations with its environment, rather than conceiving of the organism as a complex mechanical device reducible into analysable parts. The theory is firmly embedded in ecological thinking, paying attention to both organism and environment, and drawing information from their forms of interaction. Indeed, generalised tau theory has been developed by thinking specifically about the relational, or ecological invariants in engagements between organism and environment. This whole-systems approach is both ethically satisfying and intellectually illuminating to the extent that it offers not only insight into the nature of living, but also offers pragmatic, human benefits in both designing our constructed world (e.g. in cockpit design) and in therapy of movement disorders (e.g. Parkinson's Disease).

Description
General Tau Theory is the generalised theory of perceptuomotor control devised by Dave N. Lee based on the tau function. It is a theory of prospective guidance of movement. The theory deals with the purposive guidance of bodily movements, including internal movements, by means of the patterns of flow in sensory arrays and the patterns of flow of electrical energy within the nervous system.

The central idea is that movement is guided by tau-coupling motion-gaps. All purposive movement of the body, and within the body, requires guided closure of motion-gaps. A motion-gap, generally defined, is the changing gap between a current state and a goal state. Examples are the distance motion-gap between the hand and an object when reaching, the optical motion-gap between the images of the hand and object in the optic flow-field, the suction motion-gap when a baby is drawing in milk, the pitch motion- gap when a singer is sliding between notes. Tau of a motion-gap is the first-order time- to-closure of the motion-gap, i.e., the current size of the motion-gap divided by its current rate of closure. Tau-coupling means keeping the taus of two motion-gaps in constant ratio during a movement.

Experiments and Application
Theoretical analyses and experiments offer explanations, through the tau-coupling of motion-gaps, of how the taus of motion-gaps are sensed, how patterned electrical activity in the brain guides movement, how space is action-scaled, how actions are fitted into available spatio- temporal slots, how a driver controls braking and steering, how infants guide their movements, how athletes guide their movements, how musicians create expression by the way they guide their movements.