The language experience of children developing in linguistically diverse environments is subject to considerable variation both in terms of quantity and quality of language exposure. It is an open question how to investigate language exposure patterns and more important which factors are relevant for successful language learning. For example, children acquiring a minority language, including a signed language, are exposed to less variety of input than children acquiring a more global language. This is because they are living in a smaller linguistic community and with fewer occasions to use the language in everyday life. Despite this reduced input, most native signers are successful language learners. In contrast native language competence is not always achieved in signing deaf children with hearing parents or those with cochlear implants learning a spoken language. A similar outcome but with very different reasons has also been reported for hearing children with language impairment. In these populations acquisition of morphosyntactic aspects is developing atypically ending with an uncomplete linguistic repertoire. The circumstances of exposure during language development tend to differ in significant ways with respect to a large number of factors, such as, (i) length, quality and quantity of input, (ii) social status and attitudes toward the language, (iii) cognitive abilities required for language learning, and (iv) age of first exposure. Having early exposure to a range of different speakers is important in the acquisition of any language and may affect language proficiency. However, negative societal attitudes or a cognitive based disadvantage may create an unfavourable learning environment that prevents language learning from surfacing typically. This situation inevitably generates a different type of exposure for the child and consequently different language competence. In this Research Topic we intend to encourage the debate on social, linguistic and cognitive factors at play for designing an effective environment for language acquisition aiming at integrating linguistic variables coming from theoretical studies on language with environmental variables, such as, measures of language input or cognitive abilities on functions ancillary to language development.

Ever since attempts were made to describe and explain normal language development, references to exceptional circumstances have been made. Variations in the conditions under which language is acquired can be regarded as natural experiments, which would not be feasible or ethical under normal circumstances. This can throw light on such questions as: *What language input is necessary for the child to learn language? *What is the relationship between cognition and language? *How independent are different components of language function? *Are there critical periods for language development? *Can we specify necessary and sufficient conditions for language impairment? This book covers a range of exceptional circumstances including: extreme deprivation, twinship, visual and auditory impairments, autism and focal brain damage? Written in a jargon-free style, and including a glossary of linguistic and medical terminology, the book assumes little specialist knowledge. This text is suitable for both students and practitioners in the fields of psycholinguistics, developmental and educational psychology, speech pathology, paediatrics and special education.

Language acquisition is a human endeavor par excellence. As children, all human beings learn to understand and speak at least one language: their mother tongue. It is a process that seems to take place without any obvious effort. Second language learning, particularly among adults, causes more difficulty. The purpose of this series is to compile a collection of high-quality monographs on language acquisition. The series serves the needs of everyone who wants to know more about the problem of language acquisition in general and/or about language acquisition in specific contexts.

Across Europe there is increasing concern that children from migrant families frequently under-perform in state school systems. The situation makes high demands on nursery and primary teachers whose initial and continuing professional development requires appropriate re-evaluation. The Socrates-Comenius project TESSLA with experts in Estonia, France, Germany, Sweden, Turkey and the UK presents courses that comprise the relevant subject areas: bilingual language acquisition, intercultural and language awareness, language assessment, literacy development and parental involvement. Teacher educators are also provided with a discussion of appropriate methodologies, including problem-based and online learning.

How and why do all children learn language? Why do some have difficulties while others are early language learners? What are the consequences of early bilingualism? Is it possible to reach native-like competence in a foreign language? Although we still cannot fully answer these questions, research during the last two decades has begun to solve some pieces of the puzzle. This book proposes an interdisciplinary collection of writings from some of the best specialists across several fields in cognitive science, offering a wide sample of recent advances in the study of first language acquisition, bilingualism, second language acquisition, and disorders of oral language. It is addressed to all researchers and students interested in language acquisition, as well as to teachers, clinicians and parents, who will find therein many new findings and varied methodological approaches, as well as challenging questions that are still debated and in need of further research.

This book is perhaps the most stunning available demonstration of the explanatory power of the parametric approach to linguistic theory. It is akin, not to a deductive proof, but to the discovery of a footprint in a far-off place which leaves an archeologist elated. The book is full of intricate reasoning, but the stunning aspect is that the reasoning moves between not only complex syntax and diverse languages, but it makes predictions about what two-year-old children will assume about the jumble of linguistic input that confronts them. Those predictions, Hyams shows, are supported by a discriminating analysis of acquisition data in English and Italian. Let us examine the linguistic context for a moment before we discuss her theory. The ultimate issue in linguistic theory is the explanation of how a child can acquire any human language. To capture this fact we must posit an innate mechanism which meets two opposite constraints: it must be broad enough to account for the diversity of human language, and narrow enough so that the child does not make irrelevant hypotheses about his own language, particularly ones from which there is no recovery. That is, a child must not posit a grammar which permits all of the sentences of a language as well as other sentences which are not in the language. In a word, the child must not create a language in which one cannot make adult discriminations between grammatical and ungrammatical.

This book presents a comprehensive, state-of-the-art treatment of the acquisition of Indo- and Non-Indo-European languages in various contexts, such as L1, L2, L3/Ln, bi/multilingual, heritage languages, pathology as well as language impairment, and sign language acquisition. The book explores a broad mix of methodologies and issues in contemporary research. The text presents original research from several different perspectives, and provides a basis for dialogue between researchers working on diverse projects with the aim of furthering our understanding of how languages are acquired. The book proposes and refines new theoretical constructs, e.g. regarding the complexity of linguistic features as a relevant factor forming children’s, adults’ and bilingual individuals’ acquisition of morphological, syntactic, discursive, pragmatic, lexical and phonological structures. It appeals to students, researchers, and professionals in the field.

While most research on language acquisition continues to consider the individual primarily in closed-system terms, Ecology of Language Acquisition emphasizes the emergence of linguistic development through children's and learners' interactions with their environment - spatial, social, cultural, educational, and so on - bringing to light commonalities between primary language development, child and adult second-language learning, and language acquisition by robots. Such a situated, context-responsive perspective on acquisition is able to interrelate insights from a variety of paradigms and disciplines while avoiding unjustifiable appeals to normativity. The theoretical and empirical studies presented here challenge a number of dominant ideas in language acquisition theory and mark an important new research orientation. This work should be of interest to language acquisition researchers and professionals in a wide range of specialisms.