title: Propositional idea density in women's written language over the lifespan: computerized analysis.
abstract: The informativeness of written language, as measured by Propositional Idea Density (PD), has been shown to be a sensitive predictive index of language decline with age and dementia in previous research. The present study investigated the influence of age and education on the written language of three large cohorts of women from the general community, born between 1973 and 1978, 1946-51 and 1921-26. Written texts were obtained from the Australian Longitudinal Study on Women's Health in which participants were invited to respond to an open-ended question about their health. The informativeness of written comments of 10 words or more (90% of the total number of comments) was analyzed using the Computerized Propositional Idea Density Rater 3 (CPIDR-3). Over 2.5 million words used in 37,705 written responses from 19,512 respondents were analyzed. Based on a linear mixed model approach to statistical analysis with adjustment for several factors including number of comments per respondent and number of words per comment, a small but statistically significant effect of age was identified for the older cohort with mean age 78 years. The mean PD per word for this cohort was lower than the younger and mid-aged cohorts with mean age 27 and 53 years respectively, with mean reduction in PD 95% confidence interval (CI) of .006 (.003, .008) and .009 (.008, .011) respectively. This suggests that PD for this population of women was relatively more stable over the adult lifespan than has been reported previously even in late old age. There was no statistically significant effect of education level. Computerized analyses were found to greatly facilitate the study of informativeness of this large corpus of written language. Directions for further research are discussed in relation to the need for extended investigation of the variability of the measure for potential application to the identification of acquired language pathologies.
authors.affiliation: Faculty of Education and Arts, University of Newcastle, Australia; CCRE in Aphasia Rehabilitation, Australia. Electronic address: Alison.Ferguson@newcastle.edu.au.
authors.forename: Alison
authors.initials: A
authors.lastname: Ferguson
authors.affiliation: Faculty of Education and Arts, University of Newcastle, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Spencer
authors.affiliation: Faculty of Education and Arts, University of Newcastle, Australia; Centre for Linguistic and Literary Computing, University of Newcastle, Australia; Humanities Research Institute, University of Newcastle, Australia.
authors.forename: Hugh
authors.initials: H
authors.lastname: Craig
authors.affiliation: Faculty of Science and Information Technology, University of Newcastle, Australia.
authors.forename: Kim
authors.initials: K
authors.lastname: Colyvas
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D001315:Australia; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007802:Language; D007806:Language Disorders / Q000503:physiopathology*; D008137:Longitudinal Studies; D008875:Middle Aged; D018570:Risk Assessment; D055815:Young Adult
keywords: Aging; Corpus linguistics; Idea Density; Language decline; Propositional Density