His research interests focus on the intersection of linguistic insight and computational linguistics. He became interested in the detection of errors in corpus annotation after teaching a seminar on "Corpora and Linguistic Knowledge" in Spring 2002. Joined by Markus Dickinson, who had participated in the seminar, they started developing an automatic error detection method based on detecting variation of annotation across linguistically comparable instances. As reported in several papers since then (cf. publications), they have successfully applied this and related ideas to detect (and correct) errors in part-of-speech annotation as well as to continuous and discontinuous syntactic annotation - with current project work focusing on dependency annotation and data outside linguistics.