Selinker defended a PhD thesis on A Psycholinguistic Study of Transfer at Georgetown University in 1966, taught at the American University in Washington, and spent 1968 in Edinburgh's Applied Linguistics department in the company of Pit Corder. The greater part of his career was spent at the University of Michigan (1977-1993) alongside Sue Gass, following which he was professor at Birkbeck College, University of London until 2002, then visiting professor at New York University.
Selinker coined two terms in the 1970s which are fundamental to the field: interlanguage, to describe the learner's developing L2 competence, and fossilization, to refer to the end of that process of development. Later work involved the discourse domain hypothesis (with Dan Douglas) according to which second language development occurs not homogeneously but in relation to idiosyncratic topics of expertise. Selinker also co-authored an influential introduction to SLA with Susan Gass.
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