The present study directly evaluated the impact of feature sharedness on the differences between superordinate and basic-level concepts observed in semantic dementia (SD) patients. Method: For this purpose, we studied a group of 6 SD patients and a group of 12 matched controls using a sentence verification task in which we orthogonally manipulated feature sharedness (more vs. less shared) and concept level (basic level vs. superordinate). Results: Main results showed that the superordinate advantage in SD patients was observed for more shared features but not for less shared features (p < .05, ?p2 = .36). Conclusion: These results directly support the role of feature sharedness in explaining the hierarchical organization of semantic knowledge and the specific to general pattern of knowledge deterioration in SD in particular.
