Using concept typicality to explore semantic representation and control in healthy ageing.

Successful use of conceptual knowledge entails the assembling of semantic representations and control processes to access the subsets of knowledge relevant in each situation. Research has suggested that representation and control mechanisms interact to support categorization. Notably, depleted representations in semantic dementia and disrupted control processes in semantic aphasia impair categorization of atypical concepts. Yet, it remains unclear how knowledge accumulation and control decay in healthy ageing impact categorization. To address this question, we compared young and older adults' performance in a categorization task of items varying in concept typicality. Critically, older adults were more accurate in categorizing atypical concepts than the younger counterparts, as indicated by the interaction between group and typicality. Moreover, the elderly outperformed the younger in categorizing atypical concepts that were also less familiar. Thus, the decay in semantic control observed along ageing did not significantly hinder the categorization of atypical items. Our data suggest that, relative to young adults, older adults possess enriched conceptual knowledge, which supports retrieval of the category-related features needed for categorizing atypical and less familiar exemplars.