Grew up bilingual. Dad taught me another language. Learned Spanish from elementary through high school and took it from there since my locale allowed me to talk to native speakers and learn slang/informal talk. I’d love to learn more but what’s the point? Even my Spanish wanes from time to time since I rarely bother talking to people in Spanish out of nowhere with strangers.
Four isn’t bad. Sometimes I’ll write or say something that’s garbled to hell and back because my brain frizzed out.
All of this depends on:
–which languages (and the learner’s native language)
–the circumstances of the learner
–what the new languages are to be used for and how
Saying you “know” or “have learned” a language is kind of meaningless if you don’t stipulate these things.
I have a SIL who worked as a translator in Swedish (her native language), English, Norwegfian, German and Islandic. And I worked with a man who spoke English, Yiddish, Hebrew and Russian fluently.
Can I? No way. Can some other people? Apparently yes. My future son-in-law has mastered 8. (including some ancient ones)
I’ve had more than a few students over the years who were at least bilingual in high school and who added at least one more language for their doctorates. One was fluent in English, Polish and Russian and swotted up French in college.
For that matter, my cousin went through Monterey twice - once for Japanese and once for German. He picked up a fair degree of Arabic during his deployments as well. I, OTOH, still have issues with English.
My roommate in college had a German father and a Norwegian mother. They were both multilingual college professors. I always tried to be nearby when he called home because he talked to them in a pastiche of several languages.