I had an interesting discussion about language acquisition with the father of one of my younger students. He explained to me how he discovered at the age of twenty-two that he could speak fluent Italian.
He was born and grew up in southwest France, near Agen. His father’s family immigrated from Italy when his father was a very small child, so his father grew up speaking Italian at home and French in school and was perfectly bilingual. He went back to their native village for a bride. When she arrived in France, she spoke only her Italian dialect. The couple spoke Italian at home and the first child, a boy, grew up bilingual. The man I met was the second child. By the time he was born the mother had learned to speak French
Since everyone in the family spoke French and the second son heard only French outside of his home, his first words were in French. As a toddler, he sometimes heard his parents speaking to each other in Italian, but when he tried to speak Italian, they laughed at him, saying he had a French accent. He felt humiliated by their laughter and he stopped making any effort to speak Italian. Because his parents considered their Italian dialect substandard, they did not encourage the children to speak it. He told me, “It wasn’t the Italian they taught in schools.”
He went to Italy a few times as a child with his parents, who acted as interpreters for him when they visited relatives. Having grown up in a home where Italian was spoken, he understood the conversations around him, but, being shy, he never found it necessary to speak for himself. He was convinced he didn’t know how to speak Italian because he had never practiced it.
Years later, he took his French bride to Italy on a honeymoon and found that there was no one in the village who could interpret for him. So, out of necessity, he tried to communicate and quickly found the language “spilling out of his mouth”. Without ever having practiced speaking or studied conjugations, he told me that he was able to speak fluently within about three days. His wife was present and assured me that after the first couple of days he spoke easily without any hesitations. He says now that he has a slight accent and makes a few mistakes with gender but otherwise his language is grammatically correct.
This case study seems to support the view that comprehensible input is sufficient for acquisition.