Bilingual Communicative Development Inventory

The Bangor University Welsh-English bilingual communicative development inventory (BU WEB-CDI) is a questionnaire that professional and personal caregivers can fill in to tell us about a child’s language and communicative development. 

Bangor University is situated across two counties, Gwynedd and Ynys Môn, which have the highest proportion of Welsh speakers in Wales. We have close working relationships with local nurseries, schools, and clinics, making us uniquely placed to develop effective Welsh-English bilingual screening and intervention tools. 

The Bangor University WEB-CDI was developed expressly to meet a local need for suitable early years bilingual language assessment tools, and in response to a number of Welsh Government agendas. These include the Welsh language strategy, which aims to increase the number of Welsh speakers to one million by 2050, the Talk with me: Speech language and communication delivery plan, and the Healthy child Wales programme, which aims to ensure that all children in Wales meet key developmental milestones and are school ready. 

The Bangor University WEB-CDI is essential to fulfilling these agendas. A recent report commissioned by The Welsh Government identified the WEB-CDI as one of only two tools currently suitable for screening early language development in Welsh-English speaking children (see p. 63, 3.12). The second tool identified, the UK Bilingual Toddlers Assessment Tool (UKBTAT), uses Bangor University WEB-CDI data. 

The Bangor University WEB-CDI is managed by Dr. Samuel Jones and Professor Debbie Mills. All materials are available free of charge on request via A preliminary report on the Bangor WEB-CDI incorporating data from 250 children can be found here. More information about the MacArthur-Bates Communicative Development Inventories and licensed adaptations can be found here

Participate: We are actively recruiting parents across Wales to add to our large sample of normative data. If you have a child learning Welsh and/or English and would like to participate in our online survey, please contact us at 

If you use the Bangor Welsh-English Bilingual CDI in your research, please cite one of the following resources: 

Mills, D., Gathercole, V. and Ebanks, N. (2013) ‘The Bangor Welsh Communicative Development Inventory: Words and Gestures’. Bangor University. 

Jones, S., O’Riordan, C., Roch, N. & Mills, D.L. ([year accessed], [date accessed]). The Bangor Welsh-English Communicative Development Inventory. [URL for the current page]

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