Extraversion: The Unloved Variable in Applied Linguistic Research Jean-Marc Dewaele and Adrian Furnham University of London The relatively small number of linguistic studies in which extraversion is focussed on as an independent vari- able suggests that applied linguists believe it unrelated to speech production or language learning. We argue that this suspicion is based on a misunderstanding originating in the 1970s. Reappraisal of the literature suggests that extraversion may not be a predictor of success in second language learning but does affect both L1 and L2 speech production. An analysis of the psychological literature on extraversion allowed us to formulate a number of hypothe- ses about the causes of linguistic variation in the speech of introverts and extraverts. In this article we will focus on one particular psychological dimension, extraversion-introversion (first described by H. J. Eysenck in 1947), which briefly appeared in the applied linguistics literature in the 1970s (Naiman, Frohlich, Stern, & Todesco, 1978), with unrealistic expectations and insufficient understanding of the concept, before being judged irrelevant to language learning. In his review of studies on personality markers in speech, Scherer Language Learning 49:3, September 1999, pp. 509–544 509 Jean-Marc Dewaele, Department of French, Birkbeck College; Adrian Furn- ham, Department of Psychology, University College London. Correspondence concerning this article may be sent to Jean-Marc De- waele, Department of French, Birkbeck College, University of London, 43 Gordon Square, London WC1H 0PD, UK. Internet: j.dewaele@french. bbk.ac.uk