One approach to studying how children acquire language is to simulate language acquisition through computational modelling. Computational models implement theories of language acquisition and simulation outcomes can then be tested against existing real-world data or in new empirical research. It is more than ten years ago that Journal of Child Language published a special issue on the topic, edited and introduced by Brian MacWhinney (MacWhinney, 2010). Now is thus a good time to take stock of recent developments by bringing together a collection of articles that explore recent research and insights from computational modelling of child language acquisition.

Previous research on the effects of word-level factors on lexical acquisition has shown that frequency and concreteness are most important. Here, we investigate CDI data from 1,030 Dutch children, collected with the short form of the Dutch CDI, to address (i) how word-level factors predict lexical acquisition, once child-level factors are controlled, (ii) whether effects of these word-level factors vary with word class and age, and (iii) whether any interactions with age are due to differences in receptive vocabulary. Mixed-effects regressions yielded effects of frequency and concreteness, but not of word class and phonological factors (e.g., word length, neighborhood density). The effect of frequency was stronger for nouns than predicates. The effects of frequency and concreteness decreased with age, and were not explained by differences in vocabulary knowledge. These findings extend earlier results to Dutch, and indicate that effects of age are not due to increases in vocabulary knowledge.

Children who are refugees become bilingual in circumstances that are often challenging and that can vary across national contexts. We investigated the second language (L2) syntactic skills of Syrian children aged 6-12 living in Canada (n = 56) and the Netherlands (n = 47). Our goal was to establish the impact of the first language (L1 = Syrian Arabic) skills on L2 (English, Dutch) outcomes and whether L1–L2 interdependence is influenced by the length of L2 exposure. To measure L1 and L2 syntactic skills, cross-linguistic Litmus Sentence Repetition Tasks (Litmus-SRTs) were used. Results showed evidence of L1–L2 interdependence, but interdependence may only surface after sufficient L2 exposure. Maternal education level and refugee camp experiences differed between the two samples. Both variables impacted L2 outcomes in the Canadian but not in the Dutch sample, demonstrating the importance to examine refugee children’s bilingual language development in different national contexts.

Bilingualism as it occurs in current societies is a complex, multidimensional and dynamic phenomenon, calling for new approaches to capture this concept. This study shows the feasibility of a person-centred approach by combining measures of the use of and proficiency in the first and second language from 110 young Turkish–Dutch children at two measurement waves, using two existing datasets. Latent Profile Analysis revealed four profiles, equivalent at age four and six: 1) Dominant L1 use, relatively low L1 and L2 proficiency, 2) Dual L1 and L2 use, around average L1 and L2 proficiency, 3) Dominant L1 use, relatively high L1 and L2 proficiency and 4) Dominant L2 use, relatively high L2 proficiency. Latent Transition Analysis indicated that children changed in profiles over time. Regression analyses showed that profiles were differently related to the family's socioeconomic status and children's nonverbal intelligence at age four. No relations were found at age six.

This study investigates the role of parental input quality on the acquisition of Greek as a heritage language in Western Canada. Focusing on subject use, we tested four groups of Greek speakers: monolingual children, heritage children, and the parents of each one of those groups. Participants completed an elicited production task designed to elicit subject placement in wide focus and embedded interrogative contexts, where postverbal subjects are preferred/required in the monolingual variety. Results gave rise to two main conclusions: first, the parental input received by heritage children may be qualitatively different from the parental input received by monolingual children, in that it contains a higher rate of deviant preverbal subjects. Second, parental input quality in addition to quantity may affect the outcome of heritage language acquisition, in that children producing a higher rate of preverbal subjects had parents whose Greek input was not only quantitatively reduced, but also richer in preverbal subjects.

Previous research has shown that in a minority–majority language context, the quantity of language input at home is more important for the development of the minority language than for the development of the majority language. In the current study, we examined whether the same holds true for the frequency of specific language activities at home. In a group of five- and six-year-old Frisian–Dutch bilingual children (n = 120), we investigated to what extent vocabulary and morphology knowledge were predicted by reading activities, watching TV, and story-telling activities in both languages. The results showed that reading in Frisian predicted both Frisian vocabulary and morphology, while reading in Dutch only predicted Dutch vocabulary. This shows that reading at home is most important for the development of the minority language. This especially holds true for the acquisition of Frisian morphology, a domain that is known to be vulnerable in language acquisition.

While age of acquisition effects have been researched extensively in adult second language (L2) acquisition, there is less research focused on examining age of acquisition effects in child language learners. Importantly, for child learners, delays in exposure to language can occur not only for a second but also for a first language (L1). In regard to delays in exposure, it is a widespread assumption that these are detrimental to language outcomes, and that younger is always better for successful language learning. One of the aims of this special issue was to take a closer look at the evidence for this assumption with respect to language learning within the childhood years, both for delayed L1 and L2 exposure.

In this study, age of onset (AoO) was investigated in five- and six-year-old bilingual Frisian–Dutch children. AoO to Dutch ranged between zero and four and had a positive effect on Dutch receptive vocabulary size, but hardly influenced the children's accurate use of Dutch inflection. The influence of AoO on vocabulary was more prominent than the influence of exposure. Regarding inflection, the reverse was found. Accuracy at using Frisian inflection emerged as a significant predictor; this transfer effect was modulated by lexical overlap between the two languages. This study shows that ‘the sooner the better’ does not necessarily hold for language development. In fact, for the correct use of inflection, it does not matter whether children start at age zero or four. For rapidly learning words in a new language it may be helpful to first build a substantial vocabulary in the first language before learning a new language.

This study investigated the role of age-of-acquisition in determining whether young bilingual children show a pattern of L2/nonnative English, precocious BE acquisition, or whether they show the L1/native English pattern of synchronous acquisition of BE and inflectional morphology. Two groups of children with age-of-acquisition before or after 4;0 and equivalent exposure to L2 English were given production and grammaticality-judgement tasks. The children in both age-of-acquisition groups showed the precocious BE pattern, regardless of L1 background and on both tasks. We conclude that, for this aspect of morphosyntax, bilingual children who begin to learn English after age 3;0 are best characterized as child L2 rather than bilingual L1 learners.

The present study compared production and on-line comprehension of definite articles and third person direct object clitic pronouns in Greek-speaking typically developing, sequential bilingual (L2-TD) children and monolingual children with specific language impairment (L1-SLI). Twenty Turkish Greek L2-TD children, 16 Greek L1-SLI children, and 31 L1-TD Greek children participated in a production task examining definite articles and clitic pronouns and, in an on-line comprehension task, involving grammatical sentences with definite articles and clitics and sentences with grammatical violations induced by omitted articles and clitics. The results showed that the L2-TD children were sensitive to the grammatical violations despite low production. In contrast, the children with SLI were not sensitive to clitic omission in the on-line task, despite high production. These results support a dissociation between production and on-line comprehension in L2 children and for impaired grammatical representations and lack of automaticity in children with SLI. They also suggest that on-line comprehension tasks may complement production tasks by differentiating between the language profiles of L2-TD children and children with SLI.

The goal of this study was to investigate whether individual difference factors influence the second language (L2) learning of children with specific language impairment (SLI) and children with typical development (TD) differently. The study focuses on tense inflection development in English L2 children. The roles of age of L2 acquisition, length of L2 exposure, and first language (L1) were examined. Twenty-four pairs of 4- and 5-year-old English L2 children with SLI and English L2 children with TD participated in the study. Children's responses on the third person singular and regular past tense probes of the Test of Early Grammatical Impairment (Rice & Wexler, 2001) were analyzed using logistic mixed regression modeling and classification procedures. For all children, those who started learning English later performed better than children who started learning English earlier, but the advantage of an older age of acquisition was particularly present in the L2 with SLI group. For children in the L2 group with TD, their accuracy with tense inflection clearly increased with longer L2 exposure, but this was not found for the L2 children with SLI. Finally, L2 children with TD were better able to transfer L1 knowledge than L2 children with SLI.

It has been argued that children learning a second language (L2) omit agreement inflection because of communication demands. The conclusion of these studies is that L2 children know the morphological and syntactic properties of agreement inflection, but sometimes insert an inflectional default form (i.e., the bare verb) in production. The present study focuses on factors that explain errors with subject–verb agreement in the speech of children learning Dutch as their L2. Analyses of experimentally obtained production data from 4- to 9-year-old L2 children reveal that verb form, sentence position, home language, and L2 proficiency determine accuracy with subject–verb agreement in the L2. Most errors were omissions of inflection, in line with the above hypothesis. However, in more exceptional contexts, the children also substituted verb forms, which is more difficult to reconcile with the claim that L2 children's errors reflect insertion of a default form.