Parents of toddlers master a patois spoken by a population of one. We come to understand the various mixtures of missing consonants or inappropriate vowels. Then repeat back to the one the correct pronunciation.
A section of the brain is devoted to tracking how they use the phonemes. Then mapping that to meaning. Basically it is like learning an almost foreign language. The usage is similar. The grammar is simpler though growing more complex over time.
Polymath Parent 