Before the beginning of the Journal of Child Language in 1974 three technological innovations had set the stage for a fundamental expansion and revision of our understanding of the processes of child language acquisition. Portable audio and video recorders changed both the quantity and quality of data. Computers made it possible to store and search large corpora, to rapidly carry out statistical analyses of the distribution of linguistic forms and their changes over time, and to simulate models of acquisition. This essay is a personal and historical overview of the unexpected consequences of those technological innovations for the study of child language. In looking to the future, another tool, linguistic typology, is essential for building models of language acquisition.

Perusing early issues of this Journal from nearly forty years ago, we find many topics on the contents lists that could appear in a current issue. But the resources available to contributors for addressing questions of interest have changed dramatically, not least in the public availability of data. Here we look briefly at two assets which have accrued to the field in the intervening decades, and at the contributions they make. CHILDES provides a level playing field on which debates about the import of language sample data, especially longitudinal data, can be played out. The MBCDI and its offspring encourage the collection of data from large samples of individuals and so promote the exploration of factors that may explain individual differences. Both have been major contributions to the field.

Major large-scale research projects in the early years of developmental psycholinguistics were English-based, yet even then numerous studies were available or under way in a range of different languages (Ferguson & Slobin, 1973). Since then, the field of cross-linguistic child language research has burgeoned in several directions. First, rich information is now available on the acquisition of dozens of languages from around the world in numerous language families, spearheaded by the five-volume series edited by Slobin (1985–1997) and complemented by in-depth examination of specific constructions – e.g. causative alternation, motion verbs, passive voice, subject elision, noun compounding – in various languages, culminating in an in-depth examination of the acquisition of ergativity in over a dozen languages (Bavin & Stoll, 2013). A second fruitful direction is the application of carefully comparable designs targeting a range of issues among children acquiring different languages, including: production of early lexico-grammatical constructions (Slobin, 1982), sentence processing comprehension (MacWhinney & Bates, 1989), expression of spatial relations (Bowerman, 2011), discourse construction of oral narratives based on short picture series (Hickmann, 2003) and longer storybooks (Berman & Slobin, 1994), and extended texts in different genres (Berman, 2008). Taken together, research motivated by the question of what is particular and what universal in child language highlights the marked, and early, impact of ambient language typology on processes of language acquisition. The challenge remains to operationalize such insights by means of psychologically sound and linguistically well-motivated measures for evaluating the interplay between the variables of developmental level, linguistic domain, and ambient language typology.

Children with specific language impairment (SLI) are distinguishable from typically developing children primarily in the pace and course of their language development. For this reason, they are appropriate candidates for inclusion in any theory of language acquisition. In this paper, the areas of overlap between children with SLI and those developing in typical fashion are discussed, along with how the joint study of these two populations can enhance our understanding of the language development process. In particular, evidence from children with SLI can provide important information concerning the role of language typology in language development, the optimal ages for acquiring particular linguistic details, the robustness of the bilingual advantage for children, the role of input in children's acquisition of grammatical details, the unintended influence of processing demands during language assessment, the contributions of treatment designs to the study of typically developing children, and the study of individual differences in language development.

I first outline three major developments in child language research over the past forty years: the use of computational modelling to reveal the structure of information in the input; the focus on quantifying productivity and abstraction; and developments in the explanation of systematic errors. Next, I turn to what I consider to be major outstanding issues: how the network of constructions builds up and the relationship between social and cognitive development and language learning. Finally, I briefly consider a number of other areas of importance to a psychologically realistic understanding of children's language development.

Young children are skilled language learners. They apply their skills to the language input they receive from their parents and, in this way, derive patterns that are statistically related to their input. But being an excellent statistical learner does not explain why children who are not exposed to usable linguistic input nevertheless communicate using systems containing the fundamental properties of language. Nor does it explain why learners sometimes alter the linguistic input to which they are exposed (input from either a natural or an artificial language). These observations suggest that children are prepared to learn language. Our task now, as it was in 1974, is to figure out what they are prepared with – to identify properties of language that are relatively easy to learn, the resilient properties, as well as properties of language that are more difficult to learn, the fragile properties. The new tools and paradigms for describing and explaining language learning that have been introduced into the field since 1974 offer great promise for accomplishing this task.

This paper lays out the components of a language acquisition model, the interconnections among the components, and the differing stances of nativism and empiricism about syntax. After demonstrating that parsimony cannot decide between the two stances, the paper analyzes nine examples of evidence that have been used to argue for or against nativism, concluding that most pieces of evidence are either irrelevant or suggest that language is special but need not invoke innate ideas. Two pieces of evidence – the development of home sign languages and the acquisition of Determiners – do show not just that language is special but that the child has innate syntactic content. The existential claim that nativism makes – there is at least one innate syntactic idea – is an easier claim to verify than the universal claim that empiricism makes – there are no innate syntactic ideas.

The entry into language via first words and, the acquisition of word meanings is considered from the perspective of publications in the Journal of Child Language over the past forty years. Problems in achieving word meanings include the disparate and sparse concepts available to the child from past prelanguage experience. Variability in beginning word learning and in its progress along a number of dimensions suggests the problems that children may encounter, as well as the strategies and styles they adopt to make progress. Social context and adult practices are vitally involved in the success of this process. Whereas much headway has been made over the past decades, much remains to be revealed through dynamic systems theory and developmental semiotic analyses, as well as laboratory research aimed at social context conditions.

Recent research has highlighted several areas where pragmatics plays a central role in the process of acquiring a first language. In talking with their children, adults display their uses of language in each context, and offer extensive feedback on form, meaning, and usage, within their conversational exchanges. These interactions depend critically on joint attention, physical co-presence, and conversational co-presence – essential factors that help children assign meanings, establish reference, and add to common ground. For young children, getting their meaning across also depends on realizing language is conventional, that words contrast in meaning, and that they need to observe Grice's cooperative principle in conversation. Adults make use of the same pragmatic principles as they solicit repairs to what children say, and thereby offer feedback on both what the language is and how to use it.

In the early years of the Journal of Child Language, there was considerable disagreement about the role of language input or adult–child interaction in children's language acquisition. The view that quantity and quality of input to language-learning children is relevant to their language development has now become widely accepted as a principle guiding advice to parents and the design of early childhood education programs, even if it is not yet uncontested in the field of language development. The focus on variation in the language input to children acquires particular educational relevance when we consider variation in access to academic language – features of language particularly valued in school and related to success in reading and writing. Just as many children benefit from language environments that are intentionally designed to ensure adequate quantity and quality of input, even more probably need explicit instruction in the features of language that characterize its use for academic purposes