ABSTRACT
Study of the orienting reflex has been central to behavioral and cognitive psychology (Graham, 1979; Posner & Petersen, 1990; Sokolov, 1990). Not all sensory stimuli elicit orienting. Sokolov showed that orienting could be habituated when repetition of the stimulus showed it to be without significance to the organism; thus orienting depended not only on the stimulus itself, but also on the past history of the organism. The concept of an internal mechanism that aligns the sensory system with new input, and that has sufficient information to separate novel from repeated events, provides impetus toward developing an understanding of how expectations can guide the processing of sensory signals.
