This study examined whether 30 learners of Japanese in the United States who engaged in a semesterlong video-based eTandem course made gains in global language comprehensibility, that is, ease of understanding (Derwing & Munro, 2009), and what linguistic correlates contributed to these gains. Speech excerpts from Week 2 and 8 of tandem interactions were retrieved and later assessed subjectively and objectively for global comprehensibility and its linguistic correlates (lexical appropriateness, lexical richness, speech rate, and morphological accuracy) in a pre/posttest sample design. The results revealed that, although the group made significant gains in vocabulary and some gains in grammar, improvement in overall comprehensibility was subject to considerable individual variability. According to a follow-up cluster analysis and discriminant analysis, increase in speech rate was the strongest predictor of those individuals who improved comprehensibility. The findings suggest that telecollaborative interaction may promote the development of vocabulary and, to some extent, grammar, but that significant gains in comprehensibility come mostly from the fluency trait of speech rate and may require longer interactional intervention. The findings have implications for the design of telecollaboration that supports second language learning.Keywords: telecollaboration/eTandem; comprehensibility; fluency; vocabulary; L2 interaction; corrective feedback; longitudinal INTERNET-MEDIATED COMMUNICATION technology has made it possible to connect with people who do not share the same physical space. Accordingly, interacting with the target language community, which used to be achieved via physical mobility (e.g., study abroad), is (Kern, 2014). Many language practitioners nowadays incorporate such online intercultural communication in order to enhance language teaching and learning. Thus, Belz (2003) defines telecollaboration as "institutionalized, electronically mediated intercultural communication under the guidance of a languacultural expert (i.e., a teacher) for the purpose of foreign language learning and the development of intercultural competence" (p. 2).
2The Modern Language Journal 100 (2016) Among many possible approaches to telecollaboration, one of the most commonly adopted models is eTandem (Cziko, 2004), in which a pair of learners with different first languages team up and help each other learn their respective languages by making "native speaker voices a central part of the language learning experience" (O'Rourke, 2007, p. 42). In this particularly autonomous yet collaborative learning set-up, learners are expected to work for mutual understanding via negotiation for meaning (Long, 1996) and to provide corrective feedback, which is considered the "central overtly pedagogical element of a tandem partnership" (Little et al., 1999, p. 39).Despite the increasing interest in telecollaboration, however, very few studies have documented the development of oral proficiency at a macro level. This is in contrast with pre...