Conversational versus expository discourse: a study of syntactic development in children, adolescents, and adults.

In this cross-sectional investigation, syntactic development was compared in conversational versus expository discourse in 120 typically developing children, adolescents, and adults, age 7 to 49 years. Each participant was asked to discuss common topics such as school, family, and friends to elicit conversational discourse and to explain the rules and strategies of a favorite game or sport to elicit expository discourse. The results showed greater syntactic complexity in expository discourse than in conversational for all age groups, supporting the view that complex thought is driving the development of complex language. For both genres, growth in syntax continued throughout childhood and adolescence and into early adulthood (age 20-29 years) and remained stable into middle age (age 40-49 years). The 2 best indicators of growth were mean length of T-unit and relative clause production, both of which showed age-related increases into early adulthood. Another variable that was sensitive to growth was the total number of T-units produced, a measure of language output. In general, older speakers talked more than younger ones regardless of genre. Despite the statistically significant group effects, there were wide individual differences. For example, in the expository genre, some of the younger children used rather elaborate syntax whereas some of the older adults spoke quite simply. Thus, it appears that individual variability can exist at all points along the age continuum, despite the trend toward greater syntactic complexity as a function of increasing chronological age.