Child-level factors associated with Spanish-English bilingual toddlers' productive vocabulary growth.

This longitudinal study-conducted in the Midwestern United States-examines the child-level factors that promote Spanish-English bilingual toddlers' (n = 47; Mage = 18.80 months; SDage = 0.57) productive vocabulary skills from 18 to 30 months of age. At 6-month intervals, caregivers reported on toddlers' Spanish and English words produced as well as their language exposure at home. Video recordings at child age 18 months yielded estimates of toddlers' speech output (word tokens per minute). In addition, at child age 18 months, caregivers reported on toddlers' linguistic skills (comprehension), demographic background (gender, household income), and nonverbal behaviors (gesture production). Results showed that toddlers were exposed to both English and Spanish and received more Spanish than English from primary caregivers; there were no significant primary caregiver input differences across time. Growth modeling revealed linear growth rates for Spanish and conceptual (Spanish, English combined) vocabulary and a curvilinear trajectory for English vocabulary. Furthermore, toddlers' Spanish and conceptual vocabularies were positively associated with their higher frequencies of token use, greater production of gesture, and greater comprehension skills, even after controlling for input. Moreover, Spanish and conceptual growth rates were positively associated with higher token use. In terms of English, toddlers' vocabulary at child age 18 months was positively associated with their comprehension skills. Toddlers' use of more gestures and tokens as well as gender (boys) influenced their English acceleration rates over time. Findings indicate that unique trajectories exist for each of a bilingual's languages and these trajectories are differentially influenced by child-level factors, including their speech output, not only exposure to language. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Spanish-English bilingual toddlers' vocabulary skills: The role of caregiver language input and warmth.

There is a well-documented link between bilingual language development and the relative amounts of exposure to each language. Less is known about the role of quality indicators of caregiver-child interactions in bilingual homes, including caregiver input diversity, warmth and sensitivity. This longitudinal study examines the relation between caregiver input (lexical diversity, amount), warmth and sensitivity and bilingual toddlers' subsequent vocabulary outcomes. We video-recorded caregiver-child interactions in Spanish-English Latino homes when toddlers (n = 47) were 18 months of age (M = 18.32 months; SD = 1.02 months). At the 24-month follow-up, we measured children's vocabulary as total vocabulary (English, Spanish combined) as well as within language (Spanish, English). Results revealed that Spanish lexical diversity exposure at 18 months from caregivers was positively associated with children's Spanish and total vocabulary scores at 24 months, while English lexical diversity was positively associated with children's English scores; lexical diversity and amount were highly correlated. Additionally, caregivers' warmth was positively associated with children's Spanish, English and total vocabulary scores. Together, these factors accounted for substantial variance (30-40%) in vocabulary outcomes. Notably, caregiver input accounted for more variance in single language outcomes than did caregiver warmth, whereas caregiver warmth uniquely accounted for more variance in total vocabulary scores. Our findings extend prior research findings by suggesting that children's dual language development may depend on their exposure to a diverse set of words, not only amount of language exposure, as well as warm interactions with caregivers. A video abstract of this article can be viewed at https://youtu.be/q1V_7fz5wog HIGHLIGHTS: Video-recorded observations of caregiver-child interactions revealed warmth and high sensitivity from Latino caregivers. Linguistically-detailed analyses of caregiver input revealed wide variation in the diversity of Spanish and English directed at 18-month-old bilingual toddlers. Bilingual toddlers' vocabulary (single language, total) was positively associated with caregivers' diverse input and warmth, thus extending prior findings on bilinguals' amount of language exposure. Findings suggest that caregivers' lexical diversity explains more variance in bilingual toddlers' single language outcomes, whereas warmth explains more variance in total vocabulary scores.