The representation of nouns in the mental lexicon: evidence from brain-impaired and normal speakers

"This thesis investigates the lexical representation of mass (e.g., rice, milk) and count nouns (e.g., chair, cat) in language production. The research presented focuses on how mass/count (countability) information is processed at the lexical syntactic and conceptual-semantic levels. Chapter 1 reviews and discusses previous research with language unimpaired and impaired speakers and its theoretical implications for the representation of countability information in language production and comprehension. Results support the assumption that nouns have lexical-syntactic specification for countability. Chapter 2 investigates processing of mass and count nouns and their determiners during noun phrase production with language unimpaired speakers in two picture-word interference experiments. Results showed countability congruency effects which indicate that mass/count information is represented at the level of lexical-syntax and that mass/count specific determiners compete for selection. Chapter 3 and 4 present single case studies (one in Chapter 3 and two in Chapter 4) which examine possible selective impairments of mass noun lexical-syntax in three aphasic individuals with grammatical impairment. These investigations provide further evidence for the lexical-syntactic representation of mass/count information. A series of mass/count specific tasks was used to systematically investigate countability processing in language production and comprehension. Two of the individuals, RAP (Chapter 3) and DEH (Chapter 4), were found to suffer from a lexical-syntactic impairment which affected processing of mass noun grammar and led to frequent substitutions of mass noun determiners by count noun determiners. The third case study describes (Chapter 4) the individual GEC, whose conceptual semantic impairment affected naming of mass nouns. Results of the case studies not only provide further evidence that nouns and determiners are specified for countability at the level of lexical-syntax but also reveal that this lexical-syntactic information can be influenced by conceptual-semantic information which is activated by visual properties of the stimuli. The research presented in this thesis provides evidence that nouns are lexical-syntactically specified for mass and count and that activation of this information is required for the selection of countablity congruent determiners. Results show further that activation of mass and count nouns and their determiners can be influenced by conceptual-semantic information." -- Abstract.