Dimensionless Invariants for Intentional Systems: Measuring the Fit of Vehicular Activities to Environmental Layout
Robert E. Shaw, Oded M. Flascher, and Endre E. Kadar Intentional Dynamics Laboratory Center for the Ecological Study of Perception and Action The University of Connecticut
"When in use, a tool is a sort of extension of the hand, almost an attachment to it or a part of the user's own body, and thus is no longer a part of the environment of the user. But when not in use, the tool is simply a detached object of the environment . . .the boundary between the animal and the environment is not fixed at the surface of the skin but can shift."
-- Gibson ( 1979, p. 41)
"The field of safe travel, it should be noted, is a spatial field but it is not fixed in physical space. The car is moving and the field moves with the car through space. Its point of reference is not the stationary objects of the environment, but the driver himself. It is not, however, merely the subjective experience of the driver. It exists objectively as the actual field within which the car can safely operate, whether the driver is aware of it. It shifts and changes continually, bending and twisting with the road, and also elongating or contracting, widening or narrowing, according as obstacles encroach upon it and limits its boundaries."
-- Gibson & Crooks ( 1938, p. 454, emphasis in original)