Language acquisition concerns how humans learn to understand and represent the world they live in using language. It is a term applied to the first, or native, language learned and not to any subsequent languages learned at an older age. The language can be spoken and written or it can be a manual language such as sign language.
There are three key elements in language acquisition: syntax, phonetics and vocabulary. Syntax concerns how words are put together to form sentences. Phonetics concerns how written letters sound. These sounds can range from different interpretations of the same letter as in the Latin alphabet or to using two letters for the same sound as in the Japanese hiragana and katakana alphabets. The words a person uses and their meanings are called vocabulary.
Yaska and other Sanskrit linguists in the first millennium BC argued about language acquisition. They believed that a baby learns either through an act of God or by listening to those around it. Plato, the Greek philosopher, believed that babies were born with linguistic skills, whether placed there by God or by nature. The two theories, nature and nurture, have led to continued debate throughout the studies of linguistic development.
The social interaction theory strikes a balance between nature and nurture. Lev Vygotsky, in his theories on cognitive development, believed that adult input is vital to a baby’s language acquisition, but not the only element. Ernest L. Moek put the mother as the most important element in a baby’s linguistic development, as the baby would have most contact with her. Overall, they believed that some elements of language are inbuilt, such as syntax and grammar, but others, such as vocabulary, are external.
Relational frame theory (RFT) believes that any language acquisition is by nurture alone and has nothing to do with nature. Based on B. F. Skinner’s behavioral studies, RFT posits that babies learn only through their environment. Noam Chomsky, amongst others, believes this is incorrect. Emergentism is a reaction to this that believes neither nurture nor nature can alone account for the development of languages in humans.
Studies into syntax by the likes of Chomsky have also looked into language acquisition. Most theories on syntax development reflect general theories on language development, being either via nature or nurture. Empiricism posits that evolution cannot be credited with creating a natural syntax parameter in babies. Empiricists, therefore, believe learning is the most important element.
Chomsky leads another theory called generativism, which suggests that babies do actually have an inbuilt set of syntax and grammar rules waiting to be expanded. They believe the human brain is preprogrammed with a limited set of syntax options. The baby makes sense of other people’s words using these basic options until it learns to develop them further. Generativists use the grammar convergence seen in 5-year-olds as evidence of these in-built syntax options.