How do children construct a concept of natural numbers? Past research addressing this question has mainly focused on understanding how children come to acquire the cardinality principle. However, at that point children already understand the first number words and have a rudimentary natural number concept in place. The question therefore remains;…

Associative word learning, i.e., associating a word with an object, is an important building block of early word learning for TD infants. This study investigated the development of word-I object associations by TD infants and infants and toddlers with Williams syndrome (WS), a rare genetic disorder associated with delayed language and cognitive…

What aspects of infants' prelinguistic communication are most valuable for learning to speak, and why? We test whether early vocalizations and gestures drive the transition to word use because, in addition to indicating motoric readiness, they (a) are early instances of intentional communication and (b) elicit verbal responses from caregivers. In…

To what extent do toddlers have shared vocabularies? We examined CDI data collected from 14,607 infants and toddlers in five countries and measured the amount of variability between individual lexicons during development for both comprehension and production. Early lexicons are highly overlapping. However, beyond 100 words, toddlers share more…

In many low- and middle-income countries, young children learn a mother tongue or indigenous language at home before entering the formal education system where they will need to understand and speak a country's official language(s). Thus, assessments of children before school age, conducted in a nation's official language, may not fully reflect a…

We investigated whether fine motor and expressive language skills are related in the later-born siblings of children with autism (heightened-risk, HR infants) who are at increased risk for language delays. We observed 34 HR infants longitudinally from 12 to 36 months. We used parent report and standardized observation measures to assess fine motor…

We examined gestural and verbal interactions in 226 mother-infant pairs from Mexican, Dominican, and African American backgrounds when infants were 14 months and 2 years of age, and related these interactions to infants' emerging skills. At both ages, dyads were video-recorded as they shared a wordless number book, a wordless emotion book, and…