Direct parameter specification and the concept of perception.

Stimuli that reach the sensory surface may result in perception, or serve to guide action. How are these two potential consequences of sensory stimulation related? I discuss three aspects of this problem. The conceptual aspect concerns the status of the concept of perception in an objective psychology. The methodological aspect pertains to the problem of how psychophysics is related to the assessment of performance measures. The functional aspect relates to the function(s) of perception for action control. I argue that (a) conceptually, the term perception belongs to a different level of description than the constructs of information-processing models: (b) methodologically, psychophysical judgements and performance measures are not necessarily converging operations: (c) functionally, sensory information can be used for the control of action without perception as a mediating stage (direct parameter specification). Taken together, this suggests that perception should be conceptualized not as a processing stage, but as a class of actions that serve to establish and update an internal representation of the environment.