[bluecatswim]

Can confirm. I speak 3 languages (A (English), B (my mother tongue) and C). For most of my life I monologued in some combination of A and B. When I was a NEET for a couple years it was mostly in A because I spent most of my time on the internet. When I got a job my coworkers spoke in C so (as much as I hated it) my mind quickly started to occasionally default to C.

Another thing I noticed very often is when I consume any piece of media (could be a book or a TV show) my mind very quickly picks up the peculiarities of the narrative/spoken language and stays like that for a couple days.

[cogogo]

Native English speaker that learned Spanish at 25 - now in my 40s and speak it with my wife and family. Inner monologue changed pretty quickly depending on context - long before I was fully fluent. Now flips to Spanish when I’m reading or watching something in Spanish or been with people speaking it. The hilarious thing to me is my accent still has the same faults internally and is actually worse. I can’t roll my rs in my head though I can actually do it without effort physically.

Our kids are natively bilingual, they are little but I’ll ask them about it today. Very curious how they say they think.