ABSTRACT
It is intuitively obvious to most individuals that we can attend to only a very small percentage of the many stimuli around us at any given time. It is also obvious that some objects are easily noticed (i.e., are conspicuous), whereas other inconspicuous objects may require considerable time and effort to locate. These common experiences capture the basic distinction between the two processes proposed in many models of attentional processing. Although they go by different names in different models (ambient vs. focal, automatic vs. effortful, parallel vs. serial), we adopt the terms preattentive and attentive systems of processing as used by Neisser (1967, 1976) and Julesz (1981).
