Some determining factors of the alphanumeric category effect

Abstract

The alphanumeric category effect refers to the finding that letters and digits are identified more efficiently when presented among items from the opposite category (a between-category, BC, search) than among items from the same category (a within-category, WC, search). In Experiment 1, the category effect was demonstrated for some targets, but not for others. The reasons for the selectivity of the effect were clarified by Experiment 2, in which the magnitude of the effect was correlated with the physical similarities between targets and distractors. Experiment 3 showed that, in a BC search, the physical differences between letters and digits allowed the observer to be more accurate in locating a target than in identifying it. This was not the case in a WC search, in which the observer was more accurate in identifying a target than in locating it (Experiment 4). The conclusion of these experiments is that the alphanumeric category effect is dependent upon the physical aspects of the stimulus and not the perceptual categories. © 1986 Psychonomic Society, Inc.