Mixed modeling was used to examine longitudinal changes in linguistic ability in healthy older adults and older adults with dementia. Language samples, vocabulary scores, and digit span scores were collected annually from healthy older adults and semiannually from older adults with dementia. The language samples were scored for grammatical complexity and propositional content. For the healthy group, age-related declines in grammatical complexity and propositional content were observed. The declines were most rapid in the mid 70s. For the group with dementia, grammatical complexity and propositional content also declined over time, regardless of age. Rates of decline were uniform across individuals. These analyses reveal how both grammatical complexity and propositional content are related to late-life changes in cognition in healthy older adults aswell as those with dementia. Alzheimer's disease accelerates this decline, regardless of age.

Abstract:Four measures of verbal ability derived from language sample analysis as well as 11 other measures of vocabulary, verbal fluency, and memory span were obtained from a sample of young adults and a sample of older adults. Factor analysis was used to analyze the structure of the 11 vocabulary, fluency, and span measures for each age group. Then an "extension" analysis was performed using structural modeling techniques to determine how the language samples measures were related to the other measures. One language sample measure of grammatical complexity was associated with measures of working memory including reading span and digit span; two measures, sentence length in words and a measure of lexical diversity, were associated with the vocabulary measures; the fourth measure, propositional density, was associated with the fluency measures as a measure of processing efficiency. The structure of verbal abilities in young and older adults is somewhat different, suggesting age differences in processing efficiency affecting sentence length, verbal fluency, and reading speed. Text of paper:The . The structure of verbal abilities in young and older adults. Psychology and Aging, 16, 312-322. Publisher's official version: http://psycnet.apa.org/doi/10.1037/0882-7974.16.2.312. Open Access version: http://kuscholarworks.ku.edu/dspace/. The Structure of Verbal Abilities in Young and Older AdultsVerbal abilities in adulthood have been traditionally studied by testing older adults' abilities to produce definitions (Wechsler, 1981), select synonyms (Shipley, 1940), pronounce phonologically irregular words (Grober, Sliwinski, Schwartz, & Saffran, 1991), name pictures or drawings (Dunn, Dunn, & Dunn, 1997), and rapidly retrieve words (Borkowski, Benson, & Spreen, 1967). Across a wide range of tests both longitudinally and cross-sectionally, vocabulary has been shown to increase throughout the middle adult years but to decline in late adulthood (Albert, Heller, & Milberg, 1988;Botwinick & Siegler, 1980;Eisdorfer & Wilkie, 1973;Hultsch, Hertzog, Dixon, & Small, 1998;Schaie, 1983 Schaie, , 1996Schaie & Willis, 1993).Adopting a different approach, Kemper and her colleagues have traced age-related changes to verbal ability by analyzing spontaneous speech and writing samples. Language sample analysis has been traditionally used to assess children's mastery of vocabulary and grammar (Stromswold, 1996) although experimental techniques have been more recently developed to probe children's understanding of specific grammatical constructions (McKee, 1996) and maternal vocabulary inventories (Fenson, Dale, Reznick, Thal, Bates, Hartung, Pethick, & Reilly, 1991) have been developed to standardize the assessment of children's vocabulary. In a series of studies, Kemper and her colleagues investigated older adults' use of complex syntactic constructions in oral and written language samples (Kemper, 1992;Kemper, Kynette, Rash, Sprott, & O'Brien, 1989;Kemper, Rash, Kynette, & Norman, 1990;Kynette & Kemper, 1986). For example, Kemper (19...

Young and older adults provided language samples in response to questions while walking, finger tapping, and ignoring speech or noise. The language samples were scored on 3 dimensions: fluency, complexity, and content. The hypothesis that working memory limitations affect speech production by older adults was tested by comparing baseline samples with those produced while the participants were performing the concurrent tasks. There were baseline differences: Older adults' speech was less fluent and less complex than young adults' speech. Young adults adopted a different strategy in response to the dual-task demands than older adults: They reduced sentence length and grammatical complexity. In contrast, older adults shifted to a reduced speech rate in the dual-task conditions.

Three different language samples were collected from a group of young adults, 18 to 28 years of age, and a group of elderly adults, 60 to 92 years of age: an oral questionnaire eliciting information about the adults' background, education, and current health and activities; an oral statement describing the person they most admired; and a written statement recounting the most significant event in their lives. In addition, the WAIS vocabulary and digit-span tests were administered to the adults. Age-related changes in the length, clause structure, and fluency of the adults' oral answers and oral and written statements were investigated. There was an overall decrement in the complexity of adults' oral and written statements attributable to an age-related loss of left-branching clauses which occurred in all three language samples. Correlations between the length, clause, and fluency measures from the language samples and the education, health, and WAIS vocabulary and digit-span tests revealed that better-educated adults scored higher on the WAIS vocabulary test, produced longer utterances, and used more right-branching clauses, and that adults with greater memory capacity, as measured by the WAIS Digits Backward test, produced more complex utterances and used more right-and left-branching clauses. Judges found the statements from the elderly adults to be more interesting and clearer than those from the young adults. This finding suggests that there is a trade-off between producing complex syntactic structures and producing clear and interesting prose.Despite the interest of psychologists, speech-language-hearing scientists, linguists, and educators in language development in children, language development during the adult years has received little attention (Cohen, 1981). While we now know a great deal about language development in preschool and school-age children, we commonly assume that language development "crystalizes" sometime during adolescence and, apart from the consequences of hearing loss, brain trauma, or dementia, remains uniform across the life-span. However, this assumption is not warranted in light of an

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