Analysis of a sample of a young person’s expository discourse can give information about the language structures used by the young person. ‘Clausal density‘ and ‘T-units‘ are types of complex language structures which are expected in expository discourse. Clausal density refers to the number of subordinate clauses (see glossary) used within the sample. T-units are defined as any independent clause (‘main clause’), including any dependent subordinate clauses. Thus, ‘you choose a colour’ and ‘you choose the colour you would like to be when you are playing this game against your friend who also has to choose a colour’ are both T-units. The first has no dependent clauses, whereas the second has many: ‘you choose the colour / you would like / to be /when you are playing this game / against your friend / who also has to choose a colour’.
When analysing expository discourse we also need to identify fragments. These are partial T-units, which lack a component such as the verb or the object (where required). For example, if the participant says ‘you play it with a… you choose a colour, only the clause ‘you choose a colour’ is a T-unit. The phrase ‘you play it with a…’ is NOT a T-unit because it is missing the final object: it is a fragment.
In order to analyse your transcribed expository discourse sample:
- Break the written sample into T-units. For the purposes of analysis, ignore any partial T-units (fragments). Ignore “and” and separate such sentences into separate T-units (eg “I did this and he did that” gives 2 T-units: “I did this” “he did that”) Also ignore “well”, “erm” and repetitions (e.g. “er when the um ba-when the um ball isn’t hit in the pocket” becomes “when the ball isn’t hit in the pocket”).
- Identify all subordinate clauses. Classify them as: relative (RC), adverbial (AVC) or nominal (NC).
- Calculate the clausal density by adding the number of all clauses (independent [=T-units], relative, adverbial and nominal) and dividing this by the number of T-units. Thus, a sentence with higher clausal density will have a higher figure than a sentence with lower clausal density.
- In addition, further information can be gathered as follows:
- Once you have established the total number of T-units, add up the total number of complete words used in the T-units. Divide the total word number by the number of T-units to calculate the mean T-unit length.
- Also, note down the number of fragments (incomplete T-units) in the speech sample.
When you have done this for a number of samples, you can begin to compare the samples to each other.
We have included a sample transcription to show you how to carry out this analysis. We have also included data from 5 participants whose video clips are not shown in Teen Talk. You can use this data to compare the data that you will analyse from the video clips. In addition, it may be useful for you to know that Nippold et al’s findings from their 2005 study suggest that, for a typically-developing group of 17-year-olds (roughly akin to our sample participants), the normative figure for mean T-unit length is 10.59, and for clausal density is 1.56.
Based on: Nippold, M.A., Hesketh, L.J., Duthie, J.K., Mansfield, T.C. (2005) Conversational Versus Expository Discourse: A Study of Syntactic Development in Children, Adolescents, and Adults. Journal of Speech, Language, and Hearing Research. 48, 1048-1064.