When living things and other 'sensory quality' categories behave in the same fashion: a novel category specificity effect.

In this study, the performance on semantic tests of five patients with a diagnosis of probable herpes simplex encephalitis was examined. Only one of the patients, MU, showed a marked category-specific deficit for living things, unlike the other patients. Results which closely mirrored those obtained with the category living things were found in each of the five patients for the other categories, edible substances, materials, and liquids, selected for a priori theoretical reasons. The processing of these additional categories was investigated with tasks involving naming abilities in different modalities, matching to sample, and questionnaires exploring the status of the patients' knowledge about the semantic features of both living things and exemplars of novel 'sensory quality' categories. MU showed in all tasks a comparable impairment for both living things and the other three new categories, in spite of a performance closely equivalent to that of the other four patients with man-made artefacts. This finding supports an explanation of MU's performance in terms of an impairment relating to categories highly dependent on the sensory quality of stimuli. In addition, his difficulty involved all aspects of the processing of the impaired categories.