Funded by the National Institutes of Health–Child Health and Human Development
Language development is universal across human cultures, but languages differ in all aspects of their structure. Thus, language is the ideal medium to study the interaction of nature and nurture in humans.
Those aspects of language that develop similarly across widely different languages reveal universal (possibly innate?) properties of children and language.
Those aspects of language that develop differently across languages show how the child changes/adjusts based on environmental influences. This gives us clues to how the environment influences the child.
Most research comparing language development across languages has looked at what children say. However, parents and caregivers usually believe that toddlers understand more than they can say. Thus, we use comprehension methods that allow us to tap into understanding with little inconvenience to the child or the parent.
Languages We Have Studied (so far):
Two-year-olds learn verbs easily and pay attention to sentence structure when learning both novel verbs and conventional English verbs.
The unique format of prepositions helps French learners with verb acquisition!
Young Spanish learners also pay attention to sentence structure when learning motion verbs, while older children are also sensitive to lexical/typological patterns of Spanish or English. Thus, a novel motion verb is likely to refer to a path-of-motion in Spanish (entrar/enter, bajar/descend) but a manner-of-motion in English (run, skip)
Chinese allows for its nouns to be omitted in regular conversation (e.g. Kids and parents can just say “bring!” without saying who’s the bringer or what’s to be brought). Even so, Chinese moms still distinguish different subclasses of verbs by their sentence forms and Chinese learning children, too, show sensitivity to the sentence structure of verbs. They also seem to learn verbs quicker than English learners!
Turkish, Japanese, and German:
Turkish, Japanese, and German use noun case markers to reveal who did what to whom. Young learners of these languages use both case markers and number of nouns—separately–in sentence comprehension and verb acquisition.