Apprentissage d'une langue chez l'enfant
Let us compare the languages learning abilities of a child and an adult. The people who have learned a second language during the period of childhood have a better chance to speak that language with pronunciation of someone who's that his is mother tongue unlike adults who have a better chance to speak with an incorrect accent when they speak a second language. It seems that the age does not affect the skills of learning the vocabulary of a second language. Regarding grammar there is no unanimous position. An interesting fact states that if the second language learns is close to English, adults may even be more competent than children in the mastery of English grammar. Also the way that children learn a language is different than the way the adults learn it. Children naturally associate movement and action, image and sound, objet and noun. It's the same for the sounds which are perceived differently by adults and children. Indeed children are better to detect the different sounds of a foreign language.
As we've seen children learn more easily a second language than the adults. It is logical to conclude that it is more difficult when they get older. Actually when the child becomes accustomed to his mother tongue he loses his capacity to hear and distinguish the subtlety of the sounds of a foreign language.