He earned his Ph.D. in Linguistics in 1988 from the University of Washington in Seattle, and has taught at George Mason since 1989. He is the current director of linguistics, and teaches graduate and undergraduate level courses in phonetics, phonology, second language acquisition, and exceptional phonologies. His principle research deals with language sound systems, exceptional phonologies, adult second language learning, and foreign accents. He is co-editor of Interlanguage Phonology (1987). He is also the principal investigator and administrator of the Speech Accent Archive.