The effect of a combined language and reading intervention on vocabulary growth in children with Down syndrome

We are currently in the process of undertaking a systematic literature review of existing vocabulary interventions carried out with children who have Down syndrome. Having a good insight into existing interventions in this area is very useful for us when planning our DSL+-intervention. As we work on this review we will write a post each week about a different vocabulary intervention article discovered through the review process.

The first article that we are going to present in this series of posts is by Burgoyne, Duff, Clarke, Buckley, Snowling, & Hulme (2012); they provided evidence that a combined reading and language intervention was beneficial for vocabulary development (as well as literacy development) in children with Down syndrome. This study, which is one of the very few Randomised Control Trial (RCT) studies within language intervention for children with Down syndrome, involved 57 children (primary school years 1–5) and was delivered by their teaching assistants who received training on how to implement the intervention sessions.

The experimental group received training every day in school and each session was 40 minutes long. A waiting control-group receive the intervention at a later point.

Various measures related to reading and language were completed by the children at four different time points: 1. At screening, 2. Immediately prior to intervention, 3. After 20 weeks of intervention, and 4. After 40 weeks of intervention. Each week children received 4 sessions on ‘new teaching’ and one session dedicated to revision. The reading strand of the intervention focused on teaching reading and phonics together, based on Hatcher, Hulme and Ellis (1994). The language strand of the intervention focused on teaching children new vocabulary items; aiming to result in children expressing these new words. The new words were chosen based on a set of parent checklists to determine which words many of the children did not already know or understand and therefore would be useful to the children in general. Visual support and various games e.g., matching, were used to teach the new words. 

After the first 20 weeks of individual daily intervention, the experimental group showed significantly greater improvement compared to the waiting control group on measures of taught expressive vocabulary, single word reading, letter-sound knowledge, and phoneme blending.  These measures were all proximal to the content of the intervention. No transfer effects to any other language related skills measured were found. After 40 weeks of intervention for the experimental group and 20 weeks of intervention for the waiting controls, the experimental group was still ahead of the control group on most outcome measures, but the differences between the groups were not statistically significant.
The study by Burgoyne and colleagues was well designed, using RCT, obtaining a larger sample size than other studies in this area, and providing a long training period. Nonetheless, some limitations in the study and results are also present. As the authors note, the effect size was very modest. Another point to note is the age spread of the sample; how a 5 year old with Down syndrome may respond to language and reading intervention may be very different of course to the way that a 10 year old with Down syndrome may respond to such intervention. Looking at correlations, Burgoyne et al. found that across group’s younger children experienced greater reading growth by the end of the 40 weeks. Having an age-spread sample makes it difficult to know what outcome and effect size to expect from a given intervention at a certain point in children’s development. Of course, this is a tricky issue, as achieving a large sample is important (e.g. due to power in the analysis), and due to various practicalities researchers may have to make a compromise between sample size vs age range.

Potential limitations may also relate to teaching assistants delivering the intervention; specifically, their opportunities for preparation time and training, such as in pedagogical knowledge and how this impacts intervention implementation. Webster et al. (2011) notes that there is often an ‘instinctive, but mistaken assumption that less pedagogical skill is required when teaching pupils with SEN; if anything, a higher level of skill is needed’ (pg. 15).  Those teaching assistants who have a pedagogical background appear to ensure better implementation of training, resulting in greater results (Alborz et al., 2009).

Finally, because the program included both vocabulary and reading components, it is not possible to conclude whether it is the vocabulary training or the reading that is critical or if it is the combined approach that results in the observed effect. The intervention resulted in greater reading gains relative to language gains. It would be interesting to explore the effects of only the vocabulary training or only the reading training components in a comparison group, to see how this impacts the same outcome measures.

To summarize, this RCT study by Burgoyne and colleagues had many strengths and did improve reading and language outcomes (including vocabulary) in children with Down syndrome. As is so often the case in training studies however, the effects of the intervention did not generalize to other aspects of reading and language more distal from the intervention content. As with any study, there are some issues to consider regarding these outcomes.

Look out for our second post next week discussing another vocabulary intervention article carried out with children who have Down syndrome.

Alborz, A., Pearson, D., Farrell, P., & Howes, A. (2009). The impact of adult support staff on pupils and mainstream schools. London: Department for Children, Schools and Families and Institute of Education.
Burgoyne, K., Duff, F. J., Clarke, P. J., Buckley, S., Snowling, M. J., & Hulme, C. (2012). Efficacy of a reading and language intervention for children with Down syndrome: a randomized controlled trial. Journal of Child Psychology and Psychiatry, 53(10), 1044-1053.
Hatcher, P. J., Hulme, C., & Ellis, A. W. (1994). Ameliorating early reading failure by integrating the teaching of reading and phonological skills: The phonological linkage hypothesis. Child development, 65(1), 41-57.
Webster, R., Blatchford, P., Bassett, P., Brown, P., Martin, C., & Russell, A. (2011). The wider pedagogical role of teaching assistants. School Leadership and Management, 31(1), 3-20.

-Liz Smith and Kari-Anne B. Næss-

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