An outline of a theory of action systems.

It is argued that the traditional psychological construal of the distinction between central ("open loop") and peripheral ("closed loop") neural processes is no longer tenable. A review of the relevant psychobiological research on the control of movement shows that both the central-peripheral dichotomy and the distinction between sensory and motor systems derived from that dichotomy are incompatible with what is known about the processes underlying action. Based on experimental and comparative data, a new theory of action is proposed. The basic concept of this new theory is the action system: Unlike motor systems, action systems involve sensory as well as motor processes; action systems are not organized into response hierarchies, but rather in coalitional structures of adjustable movements and postures. The phylogeny of action systems is discussed, and the eight most important action systems are distinguished in terms of their evolved distinctive functions. The difficulties of developing a taxonomy of actions for functionally specific types of behavior made up of that can be controlled is resolved by showing how kinds of action are differentiated by the kinds of affordances their components help to realize.