Relational and item-specific information as determinants of category superiority effects

Recent studies have shown that the category superiority effect--the mnemonic effect of grouping items by category--pertains largely to verbal rather than pictorial stimuli, suggesting that the category superiority effect may depend primarily upon the relative availability of relational and item-specific information in a given stimulus situation. This hypothesis was tested in two experiments, in which the level of item-specific information available per stimulus item was systematically diminished through the reduction of presentation time. This manipulation resulted in the systematic creation of significant category superiority effects for pictorial stimuli. Effects were reversed for verbal materials: They decreased with diminished presentation time. In a second experiment, the complexity of category structure was also shown to influence the category superiority effect. The category superiority effect varied predictably with manipulations of verbal and nonverbal stimulus materials, consistent with current theory concerning the processing of item-specific and relational information.