REVERSAL OF THE CONCRETENESS EFFECT IN A PATIENT WITH SEMANTIC DEMENTIA

Normal subjects are better at identifying and remembering concrete as compared to abstract words (the concreteness effect). We present data on a patient, DM, who shows the opposite pattern. DM has a progressive semantic loss due to atrophic changes in his temporal lobes, particul arly on the left. His semantic impairment predominantly involves objec t terms, with relative sparing of abstract nouns and most aspects of v erb meaning. DM showed an advantage for abstract words on a wide range of tasks (e.g. producing definitions, synonymy judgments). These data challenge accounts that attribute the concreteness effect to a quanti tative superiority at the level of the underlying conceptual represent ations. We suggest that there are qualitative differences between abst ract and concrete concepts, and that, in particular, concrete concepts are more dependent on perceptual attributes that were disproportionat ely impaired in DM. We propose, further, that perceptual components of semantic representations are associated with structures in the inferi or temporal lobe(s).