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A contentious issue in contemporary psycholinguistics is whether bilingualism enhances executive functions. Here, we report a meta-analysis of 80 studies (253 effect sizes) comparing performance of monolinguals and bilinguals on non-verbal interferencecontrol tasks, while examining potential moderators of effects on two dependent variables (DVs): global reaction time (RT) and interference cost. We used a multiverse approach to determine how robust conclusions were to several dataset construction and analysis decisions. In our "preferred" analysis, using a broad definition of bilinguals and standard versions of interference-control tasks, there was a very small but significant bilingual advantage for global RT (g =.13), which became non-significant once corrected for publication bias. For interference cost, there was a very small but significant bilingual advantage (g =.11). Effects were not significantly moderated by task or participant age, but were moderated by an interaction between age of second language acquisition (AoA) and the DV. Unexpectedly, larger effect sizes for interference cost were observed for studies involving bilinguals with late as opposed to early AoA. The multiverse analysis produced results largely consistent with the preferred analysis, confirming our conclusion that evidence for a bilingual advantage on interference-control tasks is weak.

Dosing intervals up to 8 weeks 5 days did not diminish effectiveness of NTZ therapy. Further monitoring is ongoing to evaluate if the risk of PML is reduced in patients on EID.

A developmental relationship between symbolic play and language has been long proposed, going as far back as the writings of Piaget and Vygotsky. In the current paper we build on recent qualitative reviews of the literature by reporting the first quantitative analysis of the relationship. We conducted a three-level meta-analysis of past studies that have investigated the relationship between symbolic play and language acquisition. Thirty-five studies (N = 6848) met the criteria for inclusion. Overall, we observed a significant small-to-medium association between the two domains (r = .35). Several moderating variables were included in the analyses, including: (i) study design (longitudinal, concurrent), (ii) the manner in which language was measured (comprehension, production), and (iii) the age at which this relationship is measured. The effect was weakly moderated by these three variables, but overall the association was robust, suggesting that symbolic play and language are closely related in development.

Children acquire language embedded within the rich social context of interaction. This paper reports on a longitudinal study investigating the developmental relationship between conversational turn-taking and vocabulary growth in English-acquiring children (N = 122) followed between 9 and 24 months. Daylong audio recordings obtained every 3 months provided several indices of the language environment, including the number of adult words children heard in their environment and their number of conversational turns. Vocabulary was measured independently via parental report. Growth curve analyses revealed a bidirectional relationship between conversational turns and vocabulary growth, controlling for the amount of words in children's environments. The results are consistent with theoretical approaches that identify social interaction as a core component of early language acquisition.

Humans vary in almost every dimension imaginable, and language is no exception. In this article, we review the past research that has focused on individual differences (IDs) in first language acquisition. We first consider how different theoretical traditions in language acquisition treat IDs, and we argue that a focus on IDs is important given its potential to reveal the developmental dynamics and architectural constraints of the linguistic system. We then review IDs research that has examined variation in children's linguistic input, early speech perception, and vocabulary and grammatical development. In each case, we observe systematic and meaningful variation, such that variation in one domain (e.g., early auditory and speech processing) has meaningful developmental consequences for development in higher-order domains (e.g., vocabulary). The research suggests a high degree of integration across the linguistic system, in which development across multiple linguistic domains is tightly coupled.

When engaged in conversation, both parents and children tend to re-use words that their partner has just said. This study explored whether proportions of maternal and/or child utterances that overlapped in content with what their partner had just said contributed to growth in mean length of utterance (MLU), developmental sentence score, and vocabulary diversity over time. We analyzed the New England longitudinal corpus from the CHILDES database, comprising transcripts of mother-child conversations at 14, 20, and 32 months, using the CHIP command to compute proportions of utterances with overlapping content. Rates of maternal overlap, but not child overlap, at earlier time-points predicted child language outcomes at later time-points, after controlling for earlier child MLU. We suggest that maternal overlap plays a formative role in child language development by providing content that is immediately relevant to what the child has in mind.

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