Whether we grow up with one, two, or several languages during our early years of life, many of us will learn a second, foreign, or heritage language in later years. The field of Second language acquisition (SLA, for short) investigates the human capacity to learn additional languages in late childhood, adolescence, or adulthood, after the first language --in the case of monolinguals-- or languages --in the case of bilinguals-- have already been acquired. Understanding Second Language Acquisit...