Life-span changes in syntactic complexity.

Adults' diaries were examined for age-related changes in syntactic complexity. The diaries in the longitudinal sample were kept by 8 adults, born between 1856 and 1876, for seven or more decades. The diaries in the cohort-sequential sample were kept by 10 adults born between 1820 and 1829 and recorded during 1860 to 1869 or during 1900 to 1909 and 10 adults born between 1860 and 1869 and recorded during 1900 to 1909 and again in 1940 to 1949. Sentences from the two longest, usable entries from each half-decade were analyzed. The analysis determined the incidence of left- and right-branching embeddings and of coordinate and subordinate phrases and sentence fragments as well as the mean length of sentences in words and in clauses. The analysis revealed an age-related decline in the syntactic complexity of adults' sentences.