Three case-studies, using longitudinal records of children's spontaneous speech, illustrate what happens when a child's syntax changes. The first, examining acquisition of English verb-particle constructions, shows a near-total absence of commission errors. The second, examining acquisition of prepositional questions in English or Spanish, shows that children (i) may go as long as 9 months producing both direct-object questions and declaratives with prepositional phrases, before first attempting a prepositional question; and (ii) at some point, abrubtly begin producing prepositional questions that are correctly formed for the target language. The third case study shows that in children acquiring English, the onset of verb-particle constructions occurs almost exactly when that child begins using novel noun-noun compounds. After a discussion of the implications for the nature of syntactic knowledge, and for the mechanisms by which it is acquired, two examples are presented of as-yet untested acquisitional predictions of parametric proposals in the syntax literature.

Interface Delay is a theory of syntactic development, which attempts to explain an array of constructions that are slow to develop, which are characterized by being sensitive to discourse-pragmatic considerations of the type associated with the natural semantic class of definites. The theory claims that neither syntax itself, nor the discourse-pragmatic abilities related to executive function and theory of mind themselves are slow to develop. Rather, the claim is that the nexus or interface between the two cognitive domains is slow to develop. We review the development of subjects in child Spanish as an example of this delayed growth trajectory. Further, we review evidence that a delay in the development of tense causes concomitant delays in the seemingly unrelated phenomena of non-nominative case subject pronoun use and un-inverted wh- questions.

The key aim of this special issue is to make developmental theory proposals concrete enough to evaluate with empirical data. With this in mind, I discuss proposals from the “Universal Grammar + statistics” (UG+stats) perspective for learning several morphology and syntax phenomena. I briefly review why UG has traditionally been part of many developmental theories of language, as well as common statistical learning approaches that are part of UG+stats proposals. I then discuss each morphology or syntax phenomenon in turn, giving an overview of relevant UG+stats proposals for that phenomenon, specific predictions made by each proposal, and what we currently know about how those predictions hold up. I conclude by briefly discussing where we seem to be when it comes to how well UG+stats proposals help us understand the development of morphology and syntax knowledge.

The study of language acquisition has a long and contentious history: researchers disagree on what drives this process, the relevant data, and the interesting questions. Here, I outline the Starting Big approach to language learning, which emphasizes the role of multiword units in language, and of coarse-to-fine processes in learning. I outline core predictions and supporting evidence. In short, the approach argues that multiword units are integral building blocks in language; that such units can facilitate mastery of semantically opaque relations between words; and that adults rely on them less than children, which can explain (some of) their difficulty in learning a second language. The Starting Big approach is a theory of how children learn language, how language is represented, and how to explain differences between first and second language learning. I discuss the learning and processing models at the heart of the approach and their cross-linguistic implications.

Constructivist approaches to language acquisition predict that form-function mappings are derived from distributional patterns in the input, and their contextual embedding. This requires a detailed analysis of the input, and the integration of information from different contingencies. Regarding the acquisition of morphology, it is shown which types of information leads to the induction of (lexical) categories, and to paradigm building. Regarding the acquisition of word order, it is shown how languages with fixed or variable word order profit from stable syntactic hyperschemas, but require a more detailed analyses of the form-function contingencies to identify the underlying, more specific semantic, syntactic and morphological patterns. At a theoretical level, it is shown how findings from acquisition and processing converge into new linguistic theories that aim to account for regular as well as irregular phenomena in language.

How do children learn to communicate, and what do they learn? Traditionally, most theories have taken an associative, compositional approach to these questions, supposing children acquire an inventory of form-meaning associations, and procedures for composing / decomposing them; into / from messages in production and comprehension. This paper presents an alternative account of human communication and its acquisition based on the systematic, discriminative approach embodied in psychological and computational models of learning, and formally described by communication theory. It describes how discriminative learning theory offers an alternative perspective on the way that systems of semantic cues are conditioned onto communicative codes, while information theory provides a very different view of the nature of the codes themselves. It shows how the distributional properties of languages satisfy the communicative requirements described in information theory, enabling language learners to align their expectations despite the vastly different levels of experience among language users, and to master communication systems far more abstract than linguistic intuitions traditionally assume. Topics reviewed include morphological development, the acquisition of verb argument structures, and the functions of linguistic systems that have proven to be stumbling blocks for compositional theories: grammatical gender and personal names.

The aim of the present research is to investigate the development of left and right dislocation in child French through a corpus study of three children until age 2;7 from the corpus of Lyon (Demuth & Tremblay, 2008). We extracted a total of 704 dislocations and analysed their syntactic properties. We show that (i) right dislocations are more frequent than left dislocations and (ii) left dislocations are significantly more complete than right dislocations (fewer omissions of verbs or pronouns). We compare these results to the hypothesis of Freudenthal, Pine, Jones & Gobet (2015, 2016) according to which some properties of child language can be explained by a learning mechanism from the right edge of the sentences from the input. We will show that this hypothesis can explain the general trend found in our data, but it is not sufficient to account for the entire development of dislocation in French.

Children's early vocabulary shows sex differences – with boys having smaller vocabularies than age-comparable girls – a pattern that becomes evident in both singletons and twins. Twins also use fewer words than their singleton peers. However, we know relatively less about sex differences in early gesturing in singletons or twins, and also how singletons and twins might differ in their early gesture use. We examine the patterns of speech and gesture production of singleton and twin children, ages 0;10-to-3;4, during structured parent-child play. Boys and girls – singleton or twin – were similar in speech and gesture production, but singletons used a greater amount and diversity of speech and gestures than twins. There was no effect of twin dyad type (boy-boy, girl-girl, boy-girl) on either speech or gesture production. These results confirm earlier research showing close integration between gesture and speech in singletons in early language development, and further extend these patterns to twin children.