This study examines correlations between the prosody of infant-directed speech (IDS) and children’s vocabulary size. We collected longitudinal speech data and vocabulary information from Dutch mother-child dyads with children aged 18 (N = 49) and 24 (N = 27) months old. We took speech context into consideration and distinguished between prosody when mothers introduce familiar vs. unfamiliar words to their children. The results show that IDS mean pitch predicts children’s vocabulary growth between 18 and 24 months. In addition, the degree of prosodic modification when mothers introduce unfamiliar words to their children correlates with children’s vocabulary growth during this period. These findings suggest that the prosody of IDS, especially in word-learning contexts, may serve linguistic purposes.

We introduce the blueprint of the Ontogenesis Model of the L2 Lexical Representation (OM) that focuses on the development of lexical representations. The OM has three dimensions: linguistic domains (phonological, orthographic, and semantic), mappings between domains, and networks of lexical representations. The model assumes that fuzziness is a pervasive property of the L2 lexicon: most L2 lexical representations are low resolution and the ontogenetic curve of their development does not reach the optimum (i.e., the ultimate stage of their attainment with optimal encoding) in one or more dimensions. We review the findings on lexical processing and vocabulary training to show that the OM has a potential to provide an interpretation for the results that have been treated separately and to move us forward in building a comprehensive model of L2 lexical acquisition and processing.

A critical question in the study of language development is to understand lexical and syntactic acquisition, which play different roles in speech to the extent it would be natural to surmise they are acquired differently. As measured through the comprehension and production of closed-class words, syntactic ability emerges at roughly the 400-word mark. However, a significant proportion of the developmental work uses a coarse combination of function and content words on the MacArthur-Bates Communicative Development Inventory (MB-CDI). Using the MB-CDI Wordbank database, we implemented a factor analytic approach to distinguish between lexical and syntactic development from the Words and Sentences (WS) form that involves both function words and the explicit categorizations. Although the Words and Gestures (WG) form did not share the factor structure, common WG/WS elements recapitulate the expected age-related changes. This parsing of the MB-CDI may prove simple, yet fruitful in subsequent investigation.

Bilingual children may choose to reply to utterances in one language with another language. This behavior, which we call interspeaker code-switching, reportedly varies in frequency across children yet the sources of such variation are not well understood. While its use has been linked to variation in proficiency both concurrently and longitudinally, quantitative analyses of this relationship are limited. Here we measure frequency of interspeaker code-switching in a new population, French–English bilinguals in France (ages 5–8), using parental report and relate it to children’s self-reported language attitudes and perceptions of dominance, English receptive and expressive vocabulary, and sentence repetition ability. These children use interspeaker code-switching infrequently and nearly exclusively in the direction of French. Use is predicted by children’s expressive lexical and grammatical proficiency but not their attitudes toward English and French and exhibits only a marginally significant relationship with self-reported dominance. It shows a closer relationship with proficiency than other more well studied experience variables such as current exposure and output, especially for children with lesser English use. These results support a strong link between interspeaker code-switching and proficiency but not for children’s attitudes in a context where they are generally favorable.

This study investigated conceptual transfer and lexical development for spatial adjectives using participant judgments, reaction times, and eye-tracking measures. The study focused on the Japanese adjective semai and its partially equivalent English translation narrow. The study presented participants with images depicting two rooms with slight differences in height and width and asked them to identify which room was narrower. The only variation was the language in which the instructions were given: native language (L1) instructions for two L1 control groups, second language (L2) instructions for the experimental group (L1 Japanese speakers of L2 English). The results showed fundamental differences in processing between the control groups in respect to the judgments and reaction times, but not for the eye-tracking measures. Furthermore, the experimental group’s behavior indicated a conceptual understanding of narrow that was in line with developments in proficiency, but also limited to the judgment and reaction time measures. Based on these findings, we conclude that (a) conceptual transfer affects processing on receptive language tasks, and (b) L2 conceptual representations come to resemble those of native speakers as learners develop their lexical knowledge. However, we also suggest that (c) although conceptualizations likely affect cognitive functions, our eye-tracking data were too crude to capture this.

Onomatopoeia appear in high quantities in many infants’ earliest words, yet there is minimal research in this area. Instead, findings from the wider iconicity literature are generalised to include onomatopoeia, leading to the assumption that their iconic status makes them inherently learnable, thereby prompting their early production. In this review we bring together the literature on onomatopoeia specifically and iconicity more generally to consider infants’ acquisition from three perspectives: perception, production, and interaction. We consider these findings in relation to Imai and Kita’s (2014) ‘sound symbolism bootstrapping hypothesis’ to determine whether their framework can account for onomatopoeia alongside other iconic forms.

This study aimed to investigate concerns of validity and reliability in subjective ratings of age-of-acquisition (AoA), through exploring characteristics of the individual rater. An additional aim was to validate the obtained AoA ratings against two corpora – one of child speech and one of adult speech – specifically exploring whether words over-represented in the child-speech corpus are rated with lower AoA than words characteristic of the adult-speech corpus. The results show that less than one-third of participating informants’ ratings are valid and reliable. However, individuals with high familiarity with preschool-aged children provide more valid and reliable ratings, compared to individuals who do not work with or have children of their own. The results further show a significant, age-adjacent difference in rated AoA for words from the two different corpora, thus strengthening their validity. The study provides AoA data, of high specificity, for 100 child-specific and 100 adult-specific Swedish words.

In lexical development, the specificity of phonological representations is important. The ability to build phonologically specific lexical representations predicts the number of words a child knows (vocabulary breadth), but it is not clear if it also fosters how well words are known (vocabulary depth). Sixty-six children were studied in kindergarten (age 5;7) and first grade (age 6;8). The predictive value of the ability to learn phonologically similar new words, phoneme discrimination ability, and phonological awareness on vocabulary breadth and depth were assessed using hierarchical regression. Word learning explained unique variance in kindergarten and first-grade vocabulary depth, over the other phonological factors. It did not explain unique variance in vocabulary breadth. Furthermore, even after controlling for kindergarten vocabulary breadth, kindergarten word learning still explained unique variance in first-grade vocabulary depth. Skill in learning phonologically similar words appears to predict knowledge children have about what words mean.

Naturalistic data are a useful source for language acquisition research. Recently, the emphasis has been placed on using denser corpora, in order to capture a more accurate picture of child language development. However, working with large amounts of data raises resource issues, since it is time-consuming to record and to transcribe. In this article, I focus on what would be the ideal duration of a naturalistic recording for it to be considered a representative enough sample of children's linguistic behaviours to observe the acquisition of words and sounds. Some of the results suggest that 30 minutes of recording may be enough to capture these specific developments, but these results are discussed in the perspective of what an ideal session could be.

In a preferential looking paradigm, we studied how children's looking behavior and pupillary response were modulated by the degree of phonological mismatch between the correct label of a target referent and its manipulated form. We manipulated degree of mismatch by introducing one or more featural changes to the target label. Both looking behavior and pupillary response were sensitive to degree of mismatch, corroborating previous studies that found differential responses in one or the other measure. Using time-course analyses, we present for the first time results demonstrating full separability among conditions (detecting difference not only between one vs. more, but also between two and three featural changes). Furthermore, the correct labels and small featural changes were associated with stable target preference, while large featural changes were associated with oscillating looking behavior, suggesting significant shifts in looking preference over time. These findings further support and extend the notion that early words are represented in great detail, containing subphonemic information.