Investigating the Effects of Adding Explicit Teaching and/or Signing to Story-Based Vocabulary Intervention for...

Children with language disorders, including developmental language disorder (DLD), experience challenges with word learning. Common components of vocabulary interventions include presenting target words in a story, providing explicit teaching and using sign/gesture alongside speech. However, previous studies have not investigated the relative contribution of these components, in isolation or combination.

To measure the effects of adding explicit teaching and/or augmentative signing to a story-based vocabulary intervention.

Eighteen participants, aged 7;09-15;02 years, took part in our within-participant design study. All had a language disorder; 14 with DLD, and four with an associated biomedical condition. They were taught 48 real verbs and adjectives, randomly assigned to one of four conditions, over an 8-week intervention period. In the reference condition, participants watched videos of a speech and language therapist (SLT) reading a story where target words were presented incidentally, four at a time. In the first experimental condition, the delivering SLT added explicit teaching to the reference intervention. This included: providing definitions, modelling words in sentences, requesting retrieval and employing a cueing hierarchy. The second experimental condition added augmentative signing to the reference intervention, whereby the SLT in the video signed the target words as they appeared in the story. The final experimental condition added both explicit teaching and signing. In all conditions, frequency of word presentations was controlled. Word sets were counterbalanced to minimise confounds. Outcome measures assessed vocabulary knowledge and use with: (1) a word definition task and (2) sentence generation.

Participants showed stronger progress in all experimental conditions, compared to the reference condition. Bayesian models showed that adding both explicit teaching and augmentative signing in combination to the reference intervention did not lead to greater progress than adding just one of these components. Neither participants' age nor language ability were associated with intervention progress.

Our results indicate that adding either explicit teaching or augmentative signing to story-based vocabulary intervention is similarly advantageous. Adding both does not confer additional advantage. Larger-scale studies are needed to explore differences between participants and experimental conditions.

Our study highlights the importance of evaluating systematically the contribution of potential active ingredients within interventions. In particular, analysing how they work together and separately is important, as adding more ingredients does not necessarily improve effectiveness. Our results inform vocabulary teaching, indicating that staff should incorporate either augmentative signing or explicit teaching whenever possible to support the vocabulary learning of those with language disorders.

What is already known on this subject Children with (developmental) language disorders experience difficulties with word learning, which can affect their education and social participation. Previous research indicates that story-based intervention, explicit teaching and, in some cases, augmentative signing can support vocabulary learning. However, many interventions combine multiple components, making it difficult to determine which specific components are active ingredients, responsible for progress. What this paper adds to existing knowledge This study systematically compared the effects of adding explicit teaching and/or augmentative signing to a story-based (implicit) vocabulary intervention for school-aged children with (D)LD. Our results indicate that adding explicit teaching and/or augmentative signing can lead to greater improvements in learning new verbs and adjectives than the implicit intervention alone. Combining explicit teaching and signing does not appear to lead to additional benefit. What are the potential or actual clinical implications of this work? SLTs and school staff working with children with (D)LD should prioritise incorporating either augmentative signing or explicit teaching strategies whenever feasible to support vocabulary development. Signing may be quicker to implement as this can be delivered alongside speech. Intervention choices could be tailored to children and staff's individual preferences and skills. Larger studies are required to explore differences between participants and experimental conditions.