Each year, about 40,000 children are adopted across national lines, primarily by families from North America and Western Europe. These joyful occasions mark the growth of new families and also provide the framework for a natural experiment in language development. Although most are infants and toddlers, thousands of older children are also adopted. Typically, these older children loose their birth language rapidly and become fluent speakers of their new language.
Jesse Snedeker of Harvard University believes that these older children can help us understand how infants learn their native language. Early language development follows a predictable series of milestones. Babies initially say one word at a time, and mostly use nouns (“ball”) or social words (“hi”). As they grow older their sentences become longer and more complex, as verbs (“take”) and grammatical words (“about”) begin to appear.
These changes in the infant speech could be due to the child’s increased cognitive abilities or, as Snedeker asserts, they might also simply be side effects of the learning process itself and independent of the child’s age or cognitive abilities. For example, it might be easier for children to learn the meanings of nouns because they often refer to things that we can point to or look at.
The findings, which appear in the January 2007 issue of Psychological Science, indicate that the stages used to characterize infant language development are not solely attributable to cognitive development and maturation. Children who are much older and more mature go through these same stages when they learn a new language via immersion in speech. Snedeker concludes that these stages are side effects of the processes children use to learn words and grammar.