The boundary effect, namely the infants' failures to compare small and large numerosities, is well documented in studies using visual stimuli. The prevailing explanation is that the numerical system used to process sets up to 3 is incompatible with the system employed for numbers >3. This study investigates the boundary effect in 10-month-old…

Very large numbers words such as "hundred," "thousand," "million," "billion," and "trillion" pose a learning problem for children because they are sparse in everyday speech and children's experience with extremely large quantities is scarce. In this study, we examine when children acquire the…

Although vocabulary size is thought to index children's language abilities, an increasing body of work suggests that regularities in children's vocabulary composition, particularly the proportion of shape-based nouns (e.g., cup), support language development. Here we examine initial vocabulary composition in children with hearing loss following…

Early vocabulary development benefits from diverse lexical exposures within children's language environment. However, the influence of lexical diversity on children as they enter middle childhood and are exposed to multimodal language inputs remains unclear. This study evaluates global and local aspects of lexical diversity in three…

Infants experience language in rich multisensory environments. For example, they may first be exposed to the word applesauce while touching, tasting, smelling, and seeing applesauce. In three experiments using different methods we asked whether the number of distinct senses linked with the semantic features of objects would impact word recognition…

Executive functions (EFs) emerge in the first years of life and are essential for many areas of child development. However, intraindividual developmental trajectories of EF during toddlerhood and their associations with ongoing development of language skills remain poorly understood. The present three-wave study examined these trajectories and…

Psycholinguistic research on children's early language environments has revealed many potential challenges for language acquisition. One is that in many cases, referents of linguistic expressions are hard to identify without prior knowledge of the language. Likewise, the speech signal itself varies substantially in clarity, with some productions…

When infants hear sentences containing unfamiliar words, are some language-world links (such as noun-object) more readily formed than others (verb-predicate)? We examined English learning 14-15-month-olds' capacity for linking referents in scenes with bisyllabic nonce utterances. Each of the two syllables referred either to the object's identity,…

Code-switching occurs regularly in the input to bilingual children. Yet, the effect of code-switched input on language development is unclear. To test whether word learning would be affected by code-switching, Spanish-English bilingual children (N = 45, 19 boys, Mean[subscript Age] = 5.05 years; ethnicity: 37 Hispanic/Latino, six…

Most research on early language learning focuses on the objects that infants see and the words they hear in their daily lives, although growing evidence suggests that motor development is also closely tied to language development. To study the real-time behaviors required for learning new words during free-flowing toy play, we measured infants'…

Children learn language by listening to speech from caregivers around them. However, the type and quantity of speech input that children are exposed to change throughout early childhood in ways that are poorly understood due to the small samples (few participants, limited hours of observation) typically available in developmental psychology. Here…

Pacifier use during childhood has been hypothesized to interfere with language processing, but, to date, there is limited evidence revealing detrimental effects of prolonged pacifier use on infant vocabulary learning. In the present study, parents of 12- and 24-month-old infants were recruited in Oslo (Norway). The sample included 1187 monolingual…

Blind adults display language-specificity in their packaging and ordering of events in speech. These differences affect the representation of events in "co-speech gesture"--gesturing with speech--but not in "silent gesture"--gesturing without speech. Here we examine when in development blind children begin to show adult-like…

How do children infer the meaning of a novel verb? One prominent proposal is that children rely on syntactic information in the linguistic context, a phenomenon known as "syntactic bootstrapping". For example, given the sentence "The bunny is gorping the duck," a child could use knowledge of English syntactic roles to infer…

Do mono- and bilingual children differ in the way they learn novel words in ambiguous settings? Listeners may resolve referential ambiguity by assuming that novel words refer to unknown, rather than known, objects--a response known as the "mutual exclusivity effect." Past research suggested that mono- and bilinguals differ with regard to…