Thomas brings to the project expertise in research on cognitive aspects of multilingualism. He has a background in neuropsychology, with particular experience in the design, application and interpretation of cognitive tests. Since the 1990s he has been working on the relationship between language and other cognitive functions. In recent years, he has become increasingly involved in research on the cognitive aspects of bi- and multilingualism and, in collaboration with colleagues in Hyderabad, India, he produced the largest and most thorough study to date examining the effect of bilingualism on the age of onset of different types of dementia in 648 patients. In 2014 he published the first ever study addressing the relationship between bilingualism, childhood intelligence and cognitive aging in a sample of 853 participants. He is involved in further studies examining the effects of early and late language learning in young and older adults as well as in patients with different brain disorders.