Study title

We piloted a version based on data from various Babylabs, selecting words for which comprehension significantly increased with age over this range, thus eliminating several words that have been used in previous UK versions. We recruited families throughout the UK; 4575 parents signed up and 1693 contributed data to the norming sample. Families signed up through means ranging from being introduced to the study during an NHS contact (10.3% of those signing up going on to return a completed CDI) to participating through one of a wide range of UK university Babylabs (81% of those signing up through this route completing a CDI, though some were already participating in a study involving a CDI). Participants in our stratified sample matched the UK population closely by region (eight English regions, Scotland, Wales and Northern Ireland), and were evenly matched on age and gender as far as possible with a mean number of 55 children per combination of age in completed months and gender (range 39-68). The MacArthur-Bates CDIs (Fenson et al. 1994) are standardised tools for easily assessing language and communicative development in American English, with adaptations to numerous other languages, but no version has yet been standardised in UK English. We report the norming of a MacArthur-Bates Board approved UK version of the Words and Gestures Inventory (the UK-CDI W&G) for children aged 8 to 18 months.When we study children's language development, it is crucial to know what a "typical" child can do, in order to ensure that teachers, doctors, speech and language therapists, and policy makers are properly informed. For example, it is impossible to assess the impact of socio-economic deprivation on language development without knowing accurately how many words we would typically expect UK children to speak and understand. Most language milestones occur in the first few years of life, so knowing what is typical for very young children is vital. However, it is extremely...