On the information-based regulation of movement: What Wann (1996) may want to consider.

On the basis of a critical review of studies that examined the use of temporal information i the regulation of movement, J. P. Wann (1996) concluded that here is little evidence in favor of the use of tau. Although more experimental work is certainly needed, progress can only be made if (a) the conceptual confusion emanating from a lack of distinction between specifi-cation (i.e., information) and what is specified (i.e., relevant property of the environment-actor system) is resolved, and (b) the way in which information is used in the regulation of movement is reconsidered. It is argued that continuous control models incorporating first-order time-to-contact related information ot only explain the results obtained but also allow testable accounts of the principles involved in kinematic trajectory formation. A change in the relative distance between an observer and an object (or a surface) gives rise to a change in the optic angle subtended at the point of observation by the object. Thus, a change in the optic angle may be used by an observer to detect he existence of relative motion. More-over, the pattern of change of the optic angle contains