Mind and Context in Adult Second Language Acquisition: Methods, Theory, and Practice

5. A Cognitive Neuroscience Perspective on Second Language Acquisition: The Declarative/Procedural Model

five A Cognitive Neuroscience Perspective on Second Language Acquisition: The Declarative/Procedural Model michael t. ullman key words Aphasia ■ basal ganglia ■ Broca’s area ■ critical period ■ declarative memory ■ ERP ■ estrogen ■ explicit ■ fMRI ■ frontal lobe ■ grammar ■ implicit ■ language ■ language processing ■ lexicon ■ morphology ■ neuroimaging ■ PET ■ procedural memory ■ puberty ■ second language ■ second language acquisition (SLA) ■ syntax ■ temporal lobe. 1. Introduction The neural, cognitive, and computational (i.e., neurocognitive) bases of second language acquisition and processing are still not well understood. There has been surprisingly little empirical work in this area. Data informing the specific neural substrates of second language and the relations between its neural, cognitive, and computational underpinnings have been especially sparse (e.g., what brain structures play which computational roles and how do they interact?). Given this lack of data, it is not surprising that there have been few attempts to offer integrative neurocognitive theories of second language, particularly in the context of first language and of our broader understanding of the mind and brain. In this chapter, I discuss a neurocognitive model that begins to address these theoretical gaps. According to this perspective, both first and second languages are acquired and processed by well-studied brain systems that are known to subserve particular nonlanguage functions. These brain systems are posited to play analogous roles in their nonlanguage and language functions. So our independent knowledge of the cognitive, computational, neuroanatomical , physiological, cellular, endocrine, and pharmacological bases of these systems leads to specific testable predictions about both first and second language . The model thus brings the knowledge base and empirical approaches 141 of cognitive neuroscience to bear on the study of second language acquisition (SLA). This chapter begins by discussing the broader linguistic and neurocognitive issues, along with the neurocognitive model as it pertains to normal early-learned first language (L1). Next, the background, theory, and extant empirical evidence regarding the acquisition and processing of second and subsequent languages are presented, with a focus on later-learned languages, particularly those learned after puberty. (Note that the term L2 is used in this chapter to refer only to such later-learned languages.) Finally, the chapter concludes with comparisons between the model and other perspectives and with a discussion of implications and issues for further study. 2. The Neurocognition of Lexicon and Grammar Language depends upon two mental abilities (Chomsky, 1965; Pinker, 1994). First, all idiosyncratic information must be memorized in some sort of mental dictionary, which is often referred to as the mental lexicon. The lexicon necessarily includes all words with arbitrary sound-meaning pairings, such as the noncompositional (“simple”) word cat. It must also contain other irregular—that is, not entirely derivable—word-specific information, such as whether any arguments must accompany a verb (e.g., hit requires a direct object ) and whether a word takes any unpredictable related forms (e.g., teach takes the irregular past tense taught). The mental lexicon may comprise other distinctive information as well, smaller or larger than words: bound morphemes (e.g., the -ed or -ness suffixes, as in walked or happiness) and complex linguistic structures whose meanings cannot be transparently derived from their parts (e.g., idiomatic phrases, such as kick the bucket) (Di Sciullo and Williams, 1987; Halle and Marantz, 1993). But language also consists of regularities, which can be captured by rules of grammar. The rules constrain how lexical forms combine to make complex representations and allow us to interpret the meanings of complex forms even if we have not heard or seen them before. Meanings can be derived by rules that underlie the sequential orders and hierarchical relations of lexical items and of abstract categories such as verb phrase. Such rule-governed behavior is found in various aspects of language, including phrases and sentences (syntax) and complex words such as walked or happiness (morphology). The rules are a form of mental knowledge in that they underlie our individual capacity to produce and comprehend complex forms. The learning and use of this knowledge are generally implicit—that is, not available to conscious awareness. Last, although complex representations (e.g., the regular past tense form walked ) could be computed anew each time (e.g., walk ⫹ -ed ), they could in principle also be stored in the mental lexicon. 142 internal factors Numerous theories and empirical studies have probed the neurocognitive bases of lexical and grammatical abilities in L1 (e.g., Damasio and Damasio, 1992; Elman et al., 1996; Friederici, 2002; Gleason and Ratner...