You probably take for granted, if your first language is English, that you think in English.
For the most part, if you're working in only one language, you think solely in that language. But if you have more than one language, which one do you think in?
The answer isn't always what you'd expect it to be.
Here were some of those answers.
Dream Dream Dream
I'm fluent in English, Vietnamese is my mother tongue, speak a little French. I mainly think in English since I moved to US but my dreams come in Vietnamese still ...
I was roommates with a girl from Germany for a few weeks while on a group tour of South America. She was fluent in English and German. She talked in her sleep and for the first 2 weeks I would wake up in the middle of the night speaking German to no one. I had no idea what she was saying since I didn't speak the language. After 2 weeks I woke up at 3am to her saying my name, then asking in English if we could get breakfast. She actually figured out in her sleep talking state that if she wanted to converse with me, it had to be in English. It was SO weird.
French when I speak French, English when I speak English. Sometimes English when I speak French. I'm french tho. That's weird.
I took French for about 4 years and got to the point where I was pretty good at speaking it. Never got to the point of thinking in it, but one semester I decided to take Spanish too, and there were quite a few times where I would end up writing in French or responding in French if I wasn't paying attention
I know a guy who has been living in Japan for well over a decade as an English teacher and translator. There are a couple occasions where I will be talking to him in English only for him to slightly bork his English with Japanese grammar since outside of work, he never speaks English
I can think in them all. When I'm speaking a language, I think in that language even if I'm not 100% fluent.
When I'm not speaking, I generally think in one of two languages I'm a native speaker in. I don't consciously control it. Sometimes I'm surrounded by one language and my brain randomly starts thinking in the other but usually I'll think in the language I last used.
First language: Danish
Second language: English
Third language: German
It switches between danish and english.
My first language is Swedish but I'm fluent in English and pretty much only speak English at home. (I can also understand Danish and Norwegian and speak a bit of French).
I mostly think and dream in English unless I've been speaking/reading a lot of Swedish or if I'm doing stuff where my vocabulary is lacking in English.
I started off thinking in English and then translating Spanish into English in my head. It took a lot of effort.
The weirdest thing was when I started knowing words in Spanish that I didn't know in English.
And then it was weird again when I started understanding Spanish words and sentences without having to consciously translate them into English first. It was like I would hear someone say something in Spanish and the understanding of the whole meaning of the sentence would pop into my head the same way as when someone said something in English.
I learned English much much earlier in life, so that's my default, but if I'm hearing Spanish or listening to Spanish music or media(or even sometimes when I'm not), there are a lot of times when I think in Spanish, too.
And honestly, I kind of prefer thinking in Spanish, but I'm not quite sure why. Maybe it's that the music is better?
While I was in seminary at the Southern Baptist Theological Seminary there was a professor there who was very skilled in languages.
For example, he was planning a trip to Turkey to study something, and someone asked him why he was reading a book in German and he said "The best book on [some specific part of] the Turkish language is written in German."
There was a story that might have been urban legend, but one day he was walking across the quad and the [school] president stopped him and said
"Dr. Gentry, how are things going?"
"Because I know 9 languages, but can only think in 5 of them."
None In Particular
I speak Portuguese English Spanish and German. In my house multiple languages were spoken in a mix at all times. Words in sentence weren't exactly from the same language. When I speak with my family like that. I think in no language in particular and it's second nature.
When just speaking a single language at a time, I typically think in that language
When it comes to counting it's mostly german
Nothing And Everything
I consider myself to be fairly fluent in English. My thoughts partially switched to it when I was around seventeen years old (I had been speaking a little English since I was three, but I started "seriously" studying the language only when I turned sixteen).
Currently, my inner monologue is both in English and in my native language. When I'm "giving a speech" in my head, discussing some concept with myself, I usually think in English. On the other hand, my inner voice uses my native language for the most of the mundane things, like "My exams are tomorrow, yet here I am, browsing Reddit." Also, on some rare occasions, I hear nothing and just know what I'm thinking about.