My research and teaching interests embrace a wide range of topics related to sign language, including the linguistics of British Sign Language (BSL) and other sign languages, the history and sociolinguistics of BSL and the Deaf community, the development of BSL in young children, and sign language and the brain, including developmental and acquired sign language impairments.

I have held nearly £15,000,000 in grants from UK, European and international sources, as Principal or Co-Investigator. As well as publishing the results of this research in a large number of journal articles, I have co-authored and co-edited a number of books, including Sign Language: the study of Deaf People and their Language with Jim Kyle, and The Linguistics of BSL: an Introduction with Rachel Sutton-Spence (winner of the 1999 Deaf Nation Award and 2000 British Association of Applied Linguistics Book Prize), Sign Language: an International Handbook (with Roland Pfau and Markus Steinbach), Sign Language Acquisition (with Anne Baker), Directions in sign language acquisition research (with Gary Morgan), The Signs of a Savant: Language Against the Odds (with Gary Morgan, Neil Smith and Ianthi Tsimpli) and Research Methods in Sign Language Studies: A Practical Guide (with Eleni Orfanidou and Gary Morgan).