Setting the Context
General IntroductionThis book is about the acquisition of a third language (or more additional languages) in adulthood; that is, when a bilinguala child who is a simultaneous (2L1) bilingual, a child who has sequentially acquired a second language (L2) or an adult who is a sequential L2 bilingualacquires yet another language later in life. Is learning a third (L3) or more (Ln) language different from learning an L2 or just more of the same? If the process is different or similar, what are the implications for important questions related to linguistics, psychology, cognitive science and other fields? Addressing and providing some answers to the aforementioned is the overarching goal of this book.For a very long time, it was taken for granted that all instances of nonnative, sequential language acquisition were fundamentally equivalent. Such a claim was never stated explicitly; however, standard empirical practice in the study of adult L2 acquisition across virtually all paradigms suggested that few people were preoccupied with the heterogeneous groups in so-called L2 studies before the turn of the millennium. In fact, it was not until the mid-2000s that researchers, at least those studying the acquisition of morphosyntax, began to contemplate in earnest the effect of knowing more than one previous language and thus to differentiate true L2 from multilingual learners systematically, at least with regard to L3 learners. Consequently, new questions began to emerge organically, such as the role that having more than one previously acquired system has on subsequent acquisition/processing or how this influence is selected among choices. At the time of writing this book in 2017-2018, gone are the days in which no one questioned linguistic-experience inclusion criteria in L2 acquisition. We now know that whether or not a target nonnative language is chronologically a second or later language matters a great deal for morphosyntax in the L3 initial stages and throughout L3 development. While we do not yet 1