Stability and change in developmental language disorders

In this lecture I will present data from the Surrey Communication and Language in Education Study (SCALES), a population study of language development and disorder from school entry. From an initial population of 7267 children screened at the end of reception year, a stratified subsample (n = 529) received comprehensive assessment of language (vocabulary, grammar and narrative), non-verbal ability, and behavioral difficulties at 5-6 years of age (Year 1) and 95% of the sample (n = 499) were assessed again at ages 7-8 (Year 3). Language growth was measured using both raw and standard scores in children with typical development, children with developmental language disorder (DLD), and children with language disorder associated with other clinical conditions and/or intellectual disability.

Across the first three years of school there was strong individual stability of language scores (estimated ICC = .95). Linear mixed effects models highlighted steady growth in language (raw scores), and parallel rates of growth across all three groups. There was little evidence, however, that children with language disorders were narrowing the gap with peers (z-scores). Adjusted models indicated that while non-verbal ability, socio-economic status and behavioural skills predicted initial language score (intercept), none influenced rate of language growth (slope).

From school entry, rate of language growth was remarkably similar in three groups of children with diverse language and cognitive profiles. Importantly though, children with multiple developmental challenges were not falling further behind. These findings raise important questions about the timing and goals of specialist and targeted intervention programmes.