The first stage of combinatorial speech is better described as variable than uniform. Talk of variants obscures two different aspects of language (knowledge and use) and two different aspects of language development -- acquisition of the grammar (competence) and deployment of the grammar in speaking and listening (performance). Null subjects and…

How does linguistic structure affect children's developing cardinal number knowledge? The bootstrapping theory proposes that children might use syntactic information provided by known words such as quantifiers to bootstrap the meanings of unfamiliar words such as number words. Prior studies of numeral and quantifier development have indicated that…

Vulnerability of morphosyntactic production, including grammatical aspect, has been identified in at least some children with autism spectrum disorder (ASD) exposed to typologically different languages. However, Tovar et al. (2015) found strengths in comprehending grammatical aspect in English-exposed children with ASD, suggesting that the…

Using a large sample of longitudinal assessment data from children in publicly funded infant/toddler care, preschool, and kindergarten (analytic N = 453,468), this study modeled language and literacy trajectories from early infancy through kindergarten for dual language learners (DLLs) from homes representing many different languages and their…

Previous research indicates that infant-directed speech (IDS) is usually slower than adult-directed speech (ADS) and mothers prefer placing a focused word in isolation or utterance-final position in (English) IDS, which may benefit word learning. This study investigated the speaking rate and word position of IDS in two typologically-distinct…

We investigated age-related decline in adult learning of Dutch as an additional language (Ln) in speaking, writing, listening, and reading proficiency test scores for 56,024 adult immigrants with 50 L1s who came to the Netherlands for study or work. Performance for all four language skills turned out to decline monotonically after an age of…

It is a common finding across languages that young children have problems in understanding patient-initial sentences. We used Tagalog, a verb-initial language with a reliable voice-marking system and highly frequent patient voice constructions, to test the predictions of several accounts that have been proposed to explain this difficulty: the…

Heritage language speakers struggle in European classrooms with insufficient material provided for second language (SL) learning and assessment. Considering the amount of instruments and pertinent studies in English SL, immigrant students are better prepared than their peers in Romance language settings. This study investigates how factors such as…

Given that this special issue is devoted to the acquisition and processing of inflectional morphology by second language (L2) learners, the question in the title may appear redundant. However, recent research on first language (L1) and L2 morphological processing has challenged basic assumptions about the status of inflectional morphology in…