Second Language Acquisition Facit Saltus ('Takes a Leap')

1.1 Preview of the Volume: Second Language Acquisition in Adulthood is a Discontinuous Process

In this book, the idea is discussed that the acquisition of some morphosyntactic features of the second language (L2) by adult learners is a discontinuous process. The process is discontinuous because the learning principles and the brain structures that have supported the acquisition of those features up to a certain point can be juxtaposed with different learning principles and different brain structures. The latter principles and structures do not replace the former; rather, they cohabit with them. The consequence is that L2 representations, after a point of rupture, may duplicate in an L2 learner's competence. This fact will henceforth be referred to as 'discontinuity with gemination' or, more simply, as 'discontinuity' (Section 1.4). A representation of a discontinuous learning process with gemination is given in Figure 1.1 (Section 1.2). The graph in the figure illustrates that a discontinuous process is characterized by the presence of a cut-off point breaking a continuous line. The ascending continuous line can represent how an item/structure of the target language (TL) is increasingly mastered by a learner over time. Before the cut-off point, the item can be thought of as if it is represented and mastered in just one way in a learner's competence. After the cut-off point the item is represented and mastered in two different ways. This holds because the acquisition of that item splits along two qualitatively different developmental routes. The difference between these routes is qualitative because it is grounded in L2 neurocognition. Discontinuity in second language acquisition (SLA) precisely arises when the same item starts being represented and processed differently in a learner's brain over time. Up to a certain point, some morphosyntactic items of the TL may be represented and processed by learners only statistically as psychological units or chunks (words frequently occurring together to the extent that they are perceived as a whole; see Section 2.3). After that point, the same items, if certain conditions occur, may also be represented and processed by learners grammatically, as being projections of abstract features which are implicitly noted to be relevant for that and also for other, not necessarily similar, items. The consequence of discontinuity is that some morphosyntactic items might be learned (represented and processed) twice, each time in a different way (Section 1.3). Adult L2 learners – but also native speakers (albeit to a different extent) – may become capable of switching from one way of learning to the other depending on different factors.

In this volume, a description is provided of how the switch between one way of learning and another could take place in adult SLA. The former way of learning is called 'statistical learning' (SL) and the latter 'grammatical learning' (GL). In Chapters 2 and 5 we will see that SL occurs via learners' computation over 'transition probabilities' (henceforth, TP) and bottom-up category formation, while GL occurs via learners' computation over symbolic, abstract rules and top-down category formation. SL and GL are developmentally independent from one another, but interact in a learner's competence. To put it simply, SL provides the learners' developing L2 grammar with the cognitive environment to grow and develop. In this book it is proposed that the switch between SL and GL takes place as follows. The innate capacity of implicitly tracking frequently co-occurring items (which sustains SL) would provide adult learners with the necessary cognitive ground for successive grammatical generalizations. This capacity, despite being non-language specific, also provides adult learners with the necessary means to acquire parts of the grammar of a second language. Conversely, the abstract rules of 'combinatorial grammar' (Sections 1.9 and 4.8), which sustain GL, would provide adult learners with the appropriate labels for categorizing items which are also novel (never encountered before) or not frequent enough in the input and/or that appear to be very dissimilar from the majority of other category members. In the end, SL and GL are only two different ways of learning the same kinds of grammatical structures. From a certain point onwards, these two ways both may become available to L2 adult learners. We will see (in Chapters 2 and 5) how these ways of learning may cooperate as far as the acquisition of some aspects of L2 grammar is concerned.

In this book predictions for SLA in adulthood are also discussed. It is claimed that there exist features of L2 grammar which are less likely to be learned because they cannot be learned discontinuously. Features such as null subject or wh- constituents extraction, for example, cannot be learned first statistically and then grammatically, because they imply a learner's capacity for categorizing 'over absences', that is, over empty categories or displaced items (Chapter 6). It is predicted that these non-discontinuous aspects of the grammar are more difficult to learn than discontinuous aspects of the L2 grammar (such as auxiliary selection in compound tenses in L2 Italian; see Sections 1.6 and 6.3), or even that they are unlikely to be acquired by adult L2 learners, independent of the fact that they are less frequent in the TL input (Section 6.12). It will also be suggested that discontinuous acquisition in adulthood mimics the process of early language acquisition in childhood, which is discontinuous as well. Discontinuities in childhood and in adulthood differ as to the extent to which they are successful. While the former, under normal conditions, is successful, the latter is only partially successful because the optimal neuroanatomical and neurofunctional conditions that accompany a child's brain maturation cannot be replicated in adulthood (Chapter 3).

Finally, some reasons will be also listed in this book as to why innatist (modular) and cognitive (general domain) theories are not necessarily contradictory in adult SLA research. In fact, different pieces of the TL are expected to be learned in different ways. This is because the linguistic nature of those items is different and because the neural resources at a learner's disposal change with a learner's age. If the pure grammatical computation of some aspects has become more difficult for the aging brain, the statistical pretreatment of grammatical features, which is a nonlanguage-specific competence, may become necessary. Grammatical features of the TL that, due to their nature, cannot undergo this statistical pretreatment are less likely to be learned in adulthood.

1.2 The Term 'Discontinuity' and its Meaning for SLA

The term discontinuous identifies a kind of mathematical function...