By Rebecca Day, PhD Candidate in Bilingualism (Linguistics), Bangor University

Eirini Sanoudaki, Reader in Linguistics (Bilingualism), Bangor University

Sarah Cooper, Lecturer, Bangor University Rett syndrome is a rare neurological condition that disrupts physical and linguistic development, affecting around one in 10,000 women and even fewer men. For decades, researchers assumed that people with the condition, many of whom lose speech during early childhood, were confined to a limited range of cognitive and linguistic abilities.

But in Wales, where many families are bilingual and speak both English and Welsh at home, our...