As indicated by the chapters in this volume, the orienting response and its habituation are employed both theoretically and empirically in a wide variety of areas. Thus, orienting is the subject of research by those concerned with associative learning, emotional behavior, developmental processes, cogni tion, and psychopathology. A common assumption that underlies much of this research is that orienting and habituation can tell us something about the way in which information is processed. Indeed, ever since what we now call the orienting response (OR) was first noted by Pavlov (1927), it has been associated with some aspect of information processing. Pavlov himself doc umented, albeit in an unsystematic fashion, behavioral changes associated with unexpected or novel stimulation. Because his animals oriented them selves literally toward any source of environmental change, it is hardly surprising that Pavlov referred to the behavior as a “what-is-it?” or “inves tigatory” reflex. This description, together with the fact that conditioning behavior was disrupted by investigatory reflexes, has suggested to some that what Pavlov observed in his dogs was an involuntary shift in attention. Sokolov’s work in the late 1950s and early 1960s related orienting to information processing in at least two distinct ways. First, Sokolov’s (1963) stimulus comparator model of the elicitation and habituation of orienting represents an information-processing approach in which the fundamental proposition is that responsiveness to an iterated event depends on a compar
ison between current stimulation and anticipated events. In essence, Soko lov’s approach emphasized the extrapolatory properties of both the conceptual and real nervous systems. Second, Sokolov articulated a view of the func tional significance of orienting in which he attempted to specify the way in which the response influenced the processing of subsequent events. This aspect of his theorizing has direct lineage to extensive Russian work on sensory interaction, one aspect of which was the effect of intermodality stimulation on the detection of near-threshold events.