Models of impaired lexical access in speech production

Two computational models of lexical access in aphasic speakers are compared . Both are derived from an interactive two-step theory of retrieval based o n spreading activation. The weight-decay model (Dell et al., 1997) associat es patients with deviant values of two parameters, global connection weight and global decal rate. The new semantic-phonological model characterizes p atients by two different parameters, semantic weight and phonological weigh t. We provide a detailed analysis of the properties of both models and show that the semantic-phonological model is a serious competitor to the earlie r model. Not only does it fit existing patient data as well as the weight-d ecay model does but it also has closer ties to other facts and theories in cognitive neuropsychology and psycholinguistics. (C) 2000 Academic Press.