A tentative theory of preliminary processes in orienting response (OR) elicitation is presented, based upon the observed fractionation of phasic responses in the OR context. Three hypothetical preliminary processes, which are considered to involve stimulus registration and the encoding of stimulus novelty and magnitude, interact to produce what is conceptualized as Sokolov's functional OR. The initial process of stimulus registration may have its physiological basis in primary bradycardia, and the other processes are somewhat analogous to those in dual-process theory. Such coding of stimulus parameters appears compatible with the neuronal model used by Sokolov as the basis for OR formation. The entire process of OR elicitation is considered to be steered by cortical set in the Pavlovian tradition of the dominant focus. Each hypothetical preliminary process is associated in the theory with specific physiological response measures, leading to the distinction between such components of the OR and indices of the OR (most obviously, the GSR) which generally follow the functional relationships claimed by Sokolov to characterize the OR. The present theory is compatible with a different interpretation of Sokolov's unitary OR theory than that previously current in Western psychology. © 1984.