Quantifier processing can be dissociated from numerical processing: evidence from semantic dementia patients

Quantifiers such as frequency adverbs (e.g., "always", "never") and quantity pronouns (e.g., "many", "none") convey quantity information. Whether quantifiers are processed as numbers or as general semantics has been a matter of much debate. Some neuropsychological and fMRI studies have found that the processing of quantifiers depends on the numerical magnitude comprehension system, but others have found that quantifier processing is associated with semantic representation. The selective impairment of language in semantic dementia patients provides a way to examine the above controversy. We administered a series of neuropsychological tests (i.e., language processing, numerical processing and semantic distance judgment) to two patients with different levels of severity in semantic dementia (mild vs. severe). The results showed that the two patients had intact numerical knowledge, but impairments in semantic processing. Moreover, the patient with severe/late semantic dementia showed more impairment in quantifier and semantic processing than the patient with mild/early semantic dementia. We concluded that quantifier processing is associated with general semantic processing, not with numerical processing.