I think most research on the topic is pretty vague, but from personal experience, after learning my 3 languages, adding more isn't much of a hassle (although, t

I think most research on the topic is pretty vague, but from personal experience, after learning my 3 languages, adding more isn't much of a hassle (although, to be fair, I live in a bilingual city). The 3rd language was Bulgarian, spoked by probably less than 10 million people worldwide, but it also helps to understand many similar Slavic languages. I have become much more open and exposed to other cultures, feel more comfortable traveling alone off the track (I have hitchhiked in Syria before the war, amongst other places), and I can watch news or movies in a bunch of language (from those 3, I picked up basics of other languages, and from combinations, it can be enough to manage with a lot of situations).