What causes the isolation effect?

Events that are incongruent with their prevailing context are usually very well remembered. This fact often is described as the distinctiveness effect in memory, an effect that has served as explanation not only of memory phe nomena but also of various other phenomena, including social judgment. The core laboratory paradigm for studying distinctiveness in memory research ha s long been the isolation paradigm. This paradigm, sometimes attributed to H. von Restorff (1933), yields better memory for an item categorically isol ated from surrounding items than for the surrounding items and a prop er co ntrol item, The authors offer an interpretation of the isolation effect bas ed on the analysis of the processing of similarities and differences among the items. Two experiments provide evidence for this interpretation. The re sults are discussed in the context of current theories of distinctiveness e ffects in memory. An appeal is made for a different conceptualization of di stinctiveness effects, one that treats distinctiveness as a discriminative process in memory that requires processing of both similarities and differe nces among items.