The cognate facilitation effect, a classic example of cross-language interaction in the bilingual lexicon, has mostly been studied in adults. We examined the extent to which such effects occurred in simultaneous bilingual children’s word processing, to what extent these were modulated by language dominance, and to what extent this differed between comprehension and production tasks. Simultaneous bilingual Dutch-Greek children, ranging from Dutch-dominant to Greek-dominant, performed auditory lexical decision and picture-naming tasks in an online experiment. Cognate facilitation effects emerged in both tasks but manifested themselves differently. In lexical decision, there was an interaction effect with language dominance in accuracy, while in picture naming there was a main effect in reaction times. These findings suggest that, similar to what has been found for adults, simultaneous bilingual children have an integrated lexicon, in which both languages are interactively connected. Effects may differ as a combined result of factors such as comprehension versus production and individual differences in language dominance. Importantly, despite such differences, our results show that cognate effects emerge across tasks and across a range of individual children’s language dominance, indicating that shared representations within the bilingual lexicon are accessed during both word comprehension and production.

As a result of the Covid-19 pandemic, public life in many countries ground to a halt in early 2020. The aims of this study were (i) to uncover the language practices of multilingual families during the pandemic, in general and especially regarding homeschooling; and (ii) to determine to what extent the changes in circumstance caused by the pandemic impacted children’s language use and proficiency, and family well-being. Parents from 587 families completed an online survey for 1051 children. Data were analysed using ordinal logistic regression. Our results showed that for most children, there were no changes in language use, proficiency or well-being. When there were changes, these were more likely for (families with) preschool children. Using the heritage language for homeschooling (some or all of the time) did not have a negative impact on Dutch language proficiency, but it did have a positive impact on the heritage language proficiency.

When speaking or writing, people tend to re-use the syntactic structures they recently encountered (structural priming). Individuals differ in the extent to which they are primed (primeability). Previous research has suggested that perspective-taking, that is, the ability to imagine the feelings, thoughts and perceptions of others, predicts the magnitude of priming in adults. The present study investigates if this also holds for monolingual and bilingual children. We primed the possessive structure in monolingual Dutch children and bilingual children with varying L2s. There was individual variation in children’s primeability in both groups. For both monolinguals and bilinguals, we found that the better children were at perspective-taking, the more likely they were to be primed. Dutch language proficiency also influenced children’s primeability: higher language proficiency resulted in more priming in both groups. The findings suggest that structural priming serves a social function which is mediated by perspective-taking abilities.

In a between-language lexical priming study, we examined to what extent the two languages in a simultaneous bilingual child's lexicon interact, while taking individual differences in language exposure into account. Primary-school-aged Dutch–Greek bilinguals performed a primed picture selection task combined with eye-tracking. They matched pictures to auditorily presented Dutch target words preceded by Greek prime words. Their reaction times and eye movements were recorded. We tested for effects of between-language phonological priming, translation priming, and phonological priming through translation. Priming effects emerged in reaction times and eye movements in all three conditions, at different stages of processing, and unaffected by language exposure. These results extend previous findings for bilingual toddlers and bilingual adults. Processing similarities between these populations indicate that, across different stages of development, bilinguals have an integrated lexicon that is accessed in a language-nonselective way and is susceptible to interactions within and between different types of lexical representation.

Paradis’ keynote article provides a comprehensive overview of factors influencing bilingual children’s dual language abilities. It includes the ‘usual suspects’, such as input quantity, and also highlights areas requiring further investigation, such as cognitive abilities. As such, it will no doubt serve as a valuable basis for the field as we move forward. Paradis quite rightly points out that whilst some of these factors may be unidirectionally related to language abilities, suggesting causality, for many others such relations are bi- or multidirectional and as such, caution is required in interpreting them. In order to pinpoint the nature and direction of these relations (currently absent from Figure 1 in the keynote), more complex analytic techniques are needed, as Paradis herself notes: “The relations among attitudes/identity, input and interaction, and perhaps social adjustment and wellbeing, are likely to be complex; therefore, more complex analytic techniques are needed to understand the path(s) between family attitudes about the HL on one hand, and children’s HL outcomes on the other.” (Paradis, 2023: 19). In this commentary, we provide an illustration of how the complex relationships between the variables discussed in Paradis’s keynote article could be conceptualised within a causal inference approach. We offer a modest starting point by summarising key features of causal inference modelling and by illustrating how it might help us better understand what causes what.

While most investigations of bilingualism document participants’ language background, there is an absence of consensus on how to quantify bilingualism. The high number of different language background questionnaires used by researchers and practitioners jeopardises data comparability and cross-pollination between research and practice. Using the Delphi consensus survey method, we asked 132 panellists (researchers, speech and language therapists, teachers) from 29 countries to rate 124 statements on a 5-point agreement scale. Consensus was pre-defined as 75% agreement threshold. After two survey rounds, 79% of statements reached consensus. The need for common measures to quantify bilingualism was acknowledged by 96% of respondents. Agreement was reached to document: language exposure and use, language difficulties, proficiency (when it cannot be assessed directly), education and literacy, input quality, language mixing practices, and attitudes (towards languages and language mixing). We discuss the implications of these findings for the creation of a new tool to quantify bilingual experience.

To assess the presence of cross-linguistic influence, this study compared the processing of Dutch sentences by English–Dutch and German–Dutch bilingual and Dutch monolingual children in a self-paced listening task. We combined insights from studies on child bilingualism and adult second language acquisition. Sentence structures showing partial overlap between languages were investigated (long passives), as well as structures with complete or no overlap (verb second and verb third sentences). We found evidence for syntactic co-activation of overlapping structures in the form of inhibition during listening. Syntactic, and possibly lexical, overlap between languages, and language dominance modulated effects. In particular, online cross-linguistic influence was visible only in the German–Dutch group. Furthermore, effects were most pronounced when structures partially overlapped and were absent in non-overlapping structures. Effects of online cross-linguistic influence became stronger the more German-dominant children were. Our results indicate that syntactic co-activation across languages affects sentence processing in bilingual children.

Questionnaires documenting children's bilingual experience have been used frequently in research on language and cognitive development. However, there has been little investigation of the comparability between these tools. In this review, we (i) provide a list of available questionnaires used to quantify bilingual experience in children; (ii) identify the components of bilingual experience documented across questionnaires; and (iii) discuss the comparability of the measures used to operationalise these components. In doing so, we review 48 questionnaires and identify 32 overarching constructs, manifested as 194 components, and we calculate the frequency with which they are documented. Finally, by focusing on a subset of overarching constructs (language exposure and use, activities, and current language skills), we observe high variability in how they are operationalised across tools. These findings highlight the need for greater transparency in how we document bilingualism and for more comparable measures.

Although cross-linguistic influence at the level of morphosyntax is one of the most intensively studied topics in child bilingualism, the circumstances under which it occurs remain unclear. In this meta-analysis, we measured the effect size of cross-linguistic influence and systematically assessed its predictors in 750 simultaneous and early sequential bilingual children in 17 unique language combinations across 26 experimental studies. We found a significant small to moderate average effect size of cross-linguistic influence, indicating that cross-linguistic influence is part and parcel of bilingual development. Language dominance, operationalized as societal language, was a significant predictor of cross-linguistic influence, whereas surface overlap, language domain and age were not. Perhaps an even more important finding was that definitions and operationalisations of cross-linguistic influence and its predictors varied considerably between studies. This could explain the absence of a comprehensive theory in the field. To solve this issue, we argue for a more uniform method of studying cross-linguistic influence.

Previous research has suggested that the language development of bilingual children benefits from more exposure and opportunities for language use. Typically, this research has used aggregated measures of exposure and use. The role of specific interlocutors and in particular older siblings has received comparatively little attention. In this study, we examine the impact of having an older sibling on the language environment and language development of a group of 31 bilingual Greek–Dutch toddlers aged 16 to 30 months growing up in the Netherlands. Approximately half (n = 14) of the toddlers had an older sibling. With respect to language environment, toddlers with older siblings were in general found to hear and use more Dutch at home than their first-born peers. There were however no differences between the two groups of toddlers in terms of parental language use. With respect to language development, toddlers with older siblings were found to score higher than first-born peers on measures of Dutch receptive vocabulary, productive vocabulary, and morphosyntactic complexity. For Greek, no such differences were observed. The findings are discussed in light of factors including family constellation, parental language proficiency, bilingual parenting strategies, and the wider sociolinguistic context.

The Cross-linguistic Lexical Task (CLT; Haman, Łuniewska & Pomiechowska, 2015) is a vocabulary task designed to enable cross-linguistic comparisons both across and within (bilingual) children. In this paper we assessed the validity of the CLT as a measure of language proficiency in bilingual children, by determining the extent to which (i) age-matched, monolingual Spanish-speaking and Dutch-speaking children obtained similar scores, (ii) the CLT correlated with other measures of language proficiency in monolingual and bilingual children, and (iii) whether the factors underlying the CLT's construction, i.e., target words’ estimated Age of Acquisition and Complexity Index, were predictive of children's scores. Our results showed that, while the CLT correlated with other measures and is therefore a valid means of tapping into language proficiency, caution is required when using it to compare children's language proficiency cross-linguistically, as scores for Dutch-speaking and Spanish-speaking monolinguals sometimes differed.

While numerous studies have recently shown that variation in input quantity predicts children’s rate of acquisition across a range of language skills, comparatively little is known about the impact of variation in input quality on (bilingual) children’s language development. This study investigated the relation between specific quality-oriented properties of bilingual children’s input and measures of children’s language development across a number of skills while at the same time taking family constellation into account. Participants were bilingual preschoolers (n = 50) acquiring Dutch alongside another language. Preschoolers’ receptive and productive vocabulary and morphosyntax in Dutch were assessed. Parental questionnaires were used to derive estimates of input quality. Family constellation was first operationalized as presence of a native-speaker parent and subsequently in terms of patterns of parental language use. Results showed that proportion of native input and having a native-speaker parent were never significant predictors of children’s language skills, whereas the degree of non-nativeness in the input, family constellation in terms of parental language use, and language richness were. This study shows that what matters is not how much exposure bilingual children have to native rather than non-native speakers, but how proficient any non-native speakers are.

This paper explores whether there is evidence for age and/or input effects in child L2 acquisition across three different linguistic domains, namely morphosyntax, vocabulary, and syntax–semantics. More specifically, it compares data from English-speaking children whose age of onset to L2 Dutch was between one and three years with data from children whose age of onset was between four and seven years in their acquisition of verb morphology, verb placement, vocabulary, and direct object scrambling. The main findings were that there were no significant differences between the two groups in any of these areas and, with the exception of scrambling, current amount of exposure was the only factor significantly related to children's scores. The paper discusses the theoretical significance of these findings with respect to the role of input in the language acquisition process and the claim that there is a critical period ending within (early) childhood.

Multilingual first language acquisition refers to the language development of children exposed to two or more languages from birth or shortly thereafter. Much of the research on this topic adopts a comparative approach. Bilinguals are thus compared with their monolingual peers, and trilinguals with both bilinguals and monolinguals; within children, comparisons are made between a child's two (or more) languages, and between different domains within those languages. The goal of such comparisons is to determine the extent to which language development proceeds along similar paths and/or at a similar rate across groups, languages, and domains, in order to elaborate upon the question of whether these different groups acquire language in the same way, and to evaluate how language development in multilingual settings is influenced by environmental factors. The answers to these questions have both theoretical and practical implications.

The goal of this article is to discuss the results of some of this recent research on multilingual first language acquisition by reviewing (a) properties of the developing linguistic system in a variety of linguistic domains and (b) some of the characteristics of multilingual first language acquisition that have attracted attention over the past five years, including cross-linguistic influence, dominance, and input quantity/quality. Trilingual first language acquisition is covered in a dedicated section.

The focus of this study is the acquisition of grammatical gender in Greek and Dutch by bilingual children whose other language is English. Although grammatical gender languages share the property of noun classification in terms of grammatical gender, there are important differences between the languages under investigation here in terms of both the morphological cues for gender marking available to the child and the developmental path followed by monolingual children. Dutch offers limited input cues for grammatical gender, but Greek shows consistent and regular patterns of morphological gender marking on all members of the nominal paradigm. This difference is associated with the precocious pattern of gender acquisition in Greek and the attested delay in monolingual Dutch development. We explore the development of gender in Dutch and Greek with the aim of disentangling input from age of onset effects in bilingual children who vary in the age of first exposure to Dutch or Greek. Our findings suggest that although bilingual Greek children encounter fewer difficulties in gender acquisition compared to bilingual Dutch children, amount of input constitutes a predictive factor for the pattern attested in both cases. Age of onset effects could be partly responsible for differences between simultaneous and successive bilinguals in Greek, but this is clearly not the case for Dutch. Our findings are also addressed from the more general perspective of the status of “early” and “late” phenomena in monolingual acquisition and the advantages of investigating these from the bilingual perspective.

This paper investigates the role of amount of current and cumulative exposure in bilingual development and ultimate attainment by exploring the extent to which simultaneous bilingual children's knowledge of grammatical gender is affected by current and previous amount of exposure, including in the early years. Elicited production and grammaticality judgement data collected from 136 English–Dutch-speaking bilingual children aged between three and 17 years are used to examine the lexical and grammatical aspects of Dutch gender, viz. definite determiners and adjectival inflection. It is argued that the results are more consistent with a rule-based than a piecemeal approach to acquisition (Blom, Polišenskà & Weerman, 2008a; Gathercole & Thomas, 2005, 2009), and that non-target performance on the production task can be explained by the Missing Surface Inflection Hypothesis (Haznedar & Schwartz, 1997; Prévost & White, 2000; Weerman, Duijnmeijer & Orgassa, 2011).

In her very interesting Keynote Article, Johanne Paradis gives a clear overview of recent research at the interface of bilingual development and child language disorders, and highlights its theoretical and clinical implications. She raises the challenging question of “whether bilingualism can be viewed as a kind of ‘therapy’ for SLI.” At first sight, this is perhaps a surprising question, because one of the predominant views in the literature is that bilingual children with specific language impairment (SLI) will exhibit difficulties and perhaps a “double delay.” It is this challenging question that we consider in more detail here.