The span of apprehension as a function of exposure duration

The concept of the span of apprehension derives from the assumption that visual information is processed in parallel, but there are a limited number of independent inputs that can be processed simultaneously, the limit being defined as the span. According to this notion, when a group of objects are exposed briefly and the S is required to ascertain their number, if the number of objects is below his span, the number will be perceived immediately, essentially in parallel. If the number is greater than his span, he will have to process them in sequence, by counting or otherwise. To measure the span, experimenters briefly exposed groups of dots or other objects, varying the number from trial to trial, and determined the maximum number that could be ascertained reliably by their Ss. The brevity of the exposures was considered to be important to assure that the exposed items Were not available for processing for longer than an instant, so that the Ss would be obliged to process them simultaneously. Spans obtained in this way have an average of about 8 (Woodworth and Schlosberg, 1954). There is little in the way of experimental justification for the assumption that the brevity of the exposures used in span experiments prevents sequential processing of the