The Strange Persistence of First Languages describes how first languages persist, even after they have been (apparently) replaced by a different language. For example, the first language shapes our ability recognize sounds and to understand variations, such as tones, at a very young age. Also, sometimes the first language becomes the (only?) way to communicate specific memories and emotions.

A couple of times I’ve met people who want to speak Spanish with me, even though it would be much easier for both to have the conversation in English. It turns out that they are immigrants (or sons of immigrants) who learned Spanish as their first language, but that they forgot it when they were growing up in the U.S. One of them told me that his father didn’t allow him to speak English at home. Back then, as a teenager, he saw English as a way to distance himself from his father and become independent. He later told me that after his father’s death, he started looking for opportunities to practice his Spanish again.