Studies of language in Alzheimer's disease have concluded that, along with a general cognitive decline, linguistic features are also negatively affected. Studies of the language of healthy elders also observe a linguistic decline, but one which, in contrast, is markedly less severe than that induced by dementia. We examine whether the disease can be detected from the diachronic changes in written texts and, more importantly, whether it can be clearly distinguished from normal aging. Lexical and syntactic analyses were conducted on 51 novels by three prolific literary authors: Iris Murdoch, P.D. James, and Agatha Christie. Murdoch was diagnosed with Alzheimer's disease shortly after finishing her last novel; James, at 89 years of age, continues to publish critically-acclaimed works; Christie, whose last few novels are deemed strikingly subpar compared to her previous works, presents an interesting case study of possible dementia. The lexical analysis reveals significant patterns of decline in Murdoch's and Christie's later novels, while James's rates remain relatively consistent throughout her career. The syntactic measures, though unveiling fewer significant linear trends, discover a cubic model of change in Murdoch's novels, with a deep decline around her 50s. Our findings provide support for the hypothesis that dementia, which manifests clearly in lexical features, can be detected in writing.
This is joint work with Xuan Le, Ian Lancashire, and Regina Jokel.
Graeme Hirst's research interests cover a range of topics in computational linguistics, natural language processing, and related areas of cognitive science including lexical semantics, the resolution of ambiguity in text, the preservation of author's style in machine translation, recovering from misunderstanding and non-understanding in human-computer communication, and linguistic constraints on knowledge-representation systems. He is the author of two monographs: Anaphora in Natural Language Understanding and Semantic Interpretation and the Resolution of Ambiguity, and is editor of the Synthesis book series in Human Language Technologies. He is the recipient of two awards for excellence in teaching, and has supervised more than 40 theses and dissertations, four of which have been published as books. He was elected Chair of the North American Chapter of the Association for Computational Linguistics for 2004-05 and Treasurer of the Association for 2008-2012.