Task Specific Devices and the Perceptual Bottleneck*

An approach to the problem of organization in human action is presented. The approach describes the observable forms of behavior in terms of the dynamics of task specific devices (TSD). The properties of a TSD delineate problems for research. The properties are task specificity, smartness, determinism, soft assembly and reduction, controllability, scale specificity, assembly over properties of organism and environment, and modifiability to new purpose. Nonlinear properties of four subsystems of the human action system are described. The subsystems are the link-segment system, the muscular system, the circulatory system, and the nervous system. A methodological dilemma is created by the need to do justice in description to all four subsystems while at the same time not being completely overwhelmed by the extreme complexity. A strategic resolution is to describe the simpler dynamics of TSD's. This strategy holds the promise of working backwards to the complex dynamics of the subsystems from which a TSD is assembled. Finally, TSD's require perceptual access to the dynamics. The characteristics of the human perceptual system lead to the perceptual bottleneck. Information about the dynamics of actions and events must be preserved over two mappings. One mapping is from the dynamics to the kinematics of an event. This introduces the identification problem in perception. How do the qualitative properties of an event allow an observer to recognize it? The second mapping is from the ratio-scaled kinematics of an event to the non-ratio scaled structure of the optic, acoustic, and haptic arrays. This introduces the scaling problem in perception. How do the qualitative properties of an event allow an observer to judge the scale values in an event?