Many of us are familiar with the concept of accents. Adults can learn a new language, but no matter how hard they try, they seem to struggle in mastering the language like a native speaker. It is not impossible, but it is challenging. Children, on the other hand, can master new languages and be as fluent as native speakers.
Before explaining the concept of accents, we need to define the term phoneme. Phonemes are the basic units of language. They represent the units of sounds. Humans are born with the ability to learn all phonemes, which means that they have the potential to learn any language they hear (or see! sign language works similarly to spoken language). After a couple of months, they will narrow down those phonemes to the phonemes of their parents’ language. However, they can regain some of the phonemes, but the older they get, the harder the process is, and this is why children can learn languages and master them as well as native speakers.
This made psychologists hypothesize that humans have what is called a sensitive period, during which language acquisition is most efficient. To put it simply, our brains are programmed to receive language during this period, during which the language structure, grammar, and sounds can be mastered. This holds true for first language acquisition. If no language was received during the sensitive period, there is no way to learn any language (and especially grammar) later in life. As for the second language, we can still learn and be fluent in other languages later in life, but it is very challenging to sound like native speakers. So, if you want your children to master different languages, be sure to expose them to these languages as early as possible so they can maintain the phonemes