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Intro: This study investigated the development of syntax in conversational versus expository discourse across the lifetime.

Background: Conversational tasks have long been a part of speech language assessment. Many investigations have identified markers of development in conversational discourse starting with very young children. However, very little research has been done on the development of expository discourse across the lifetime, despite evidence that speakers produce more complex language in expository tasks.

Hypothesis: The authors of the current study sought to identify markers of syntactic development in expository discourse, as well as to determine if syntactic growth continued past adolescence. The authors also intended to contribute normative data on the typical development of expository discourse as this has been lacking from the research. 

Methodology and Participants: The investigators recruited 120 participants from age 7-49 from schools and communities in western Oregon. All participants spoke English as their first language and none of the children were receiving special education or speech services. Graduate students in speech language pathology interviewed the participants. They first elicited conversation about common topics (e.g., family, pets) and then expository discourse by asking the participants to describe how to play a favorite game or sport. Researchers then analyzed conversational and expository discourse language samples for use of clauses, clausal density and mean length of t-unit. T-units were counted as one main clause with one subordinate clause. 

Conclusion: Analysis of the results demonstrated that expository tasks consistently obtained more complex language from participants of all ages as compared to the conversational task. In addition, it was also noted that mean length of t-unit (one main clause and one subordinate clause) and use of relative clauses exhibited increases into early adulthood and then remained stable into middle-age. In addition, the authors noted that mean length of t-unit is a good predictor of subordination of clauses. 

Relevance to the field: This study highlights the importance of expository tasks in eliciting the most complex language from a speaker, even in younger school-aged children during assessment or intervention. As adult-like morphology is already acquired by the early school years, expository tasks may be especially important in eliciting complex language in adolescence as conversational tasks no longer appear to sufficiently “stress” the linguistic system. In addition, the expository task more closely resembles the natural language that is necessary for school and work. These types of expository tasks similar to what is needed in school may also reveal language difficulties even in children that “pass” standardized tests.  



Nippold, M. A., Hesketh, L. J., Duthie, J. K., & Mansfield, T. C. (2005). Conversational versus expository discourse. Journal of Speech, Language, and Hearing Research. 48(5):1048-64.