Those old, familiar things: Age of acquisition, familiarity and lexical access in progressive aphasia

We present a re-analysis of a longitudinal study of the confrontation naming and verbal comprehension performance of two progressive aphasic subjects, Mary and EP, who initially presented with disturbed word-finding. We set out to establish which, if any, of a set of psycholinguistic variables known to affect performance in normal subjects influenced success at naming in these two individuals. Regression analysis suggested that Mary's performance was influenced by age of acquisition, such that words acquired early in life were more accessible than those words acquired later in life. In contrast, EP's performance was affected by familiarity, familiar words were produced with greater accuracy than less familiar words. In addition, both subjects evidenced comprehension difficulties. In EP, failure in comprehension was highly associated with failure to name. We suggest that this implies a role for familiarity in the organization of semantic memory and that this organization determines the course of breakdown in semantic dementia. In Mary's case comprehension was spared initially, suggesting that hers was due to a separate, lexical-phonological deficit. On this basis, we would argue for the involvement of age of acquisition in the access to phonological representations, with earlier acquired words remaining relatively invulnerable early in the progression.