The effect of typicality on online category verification of inanimate category exemplars in aphasia

Background: A previous study (Kiran & Thompson, 2003a) investigated the effect of typicality on online category verification of animate categories in patients with fluent or nonfluent aphasia and their normal controls. Results revealed a robust effect of typicality: typical examples were faster and more accurate than atypical examples of animate categories. Patients with fluent aphasia did not demonstrate the expected effects of typicality. Aims: The aim of the present study was to extend this work to examine the effect of typicality on inanimate categories such as furniture, clothing, and weapons. Methods & Procedures: Normal young, older, and aphasic individuals participated in an online category verification task where primes were superordinate category labels whereas targets were either typical or atypical examples of inanimate categories (e. g., clothing, furniture, weapons) or nonmembers belonging to animate categories. Aphasic participants were divided into two groups, semantic impairment group (SI) and no semantic impairment group (NSI), based on their performance on offline standardised semantic processing tests. The reaction time to judge whether the target belonged to the preceding category label was measured. Outcomes & Results: Results indicated that all four groups were significantly faster and more accurate on typical examples compared to atypical examples. Further, differences emerged in the processing of categories, wherein responses to clothing were more accurate than responses to furniture or weapons. In the SI group, representation of typical examples and atypical examples were impaired, as evidenced by poor accuracy rates. Conclusions: The present experiment demonstrated the typicality effect in normal individuals and in individuals with aphasia. Further, differences emerged in the processing of categories, where responses to clothing were more accurate than responses to furniture or weapons.