I could be wrong here, but it seems to me that a common aspect amongst all languages is the tendency to raise the pitch of your voice slightly when asking a question. Especially at the end of a question sentence.
If I’m wrong about this raised pitch being common amongst all languages, at the very least do all languages change their tone slightly to indicate that a question is being asked?
I guess there needs to be some way to indicate what is and isn’t a question. Perhaps a higher pitched voice reflects uncertainty. Is this something deep rooted in humans, or just an arbitrary choice when language developed?
I was expecting Mandarin to be an exception, since the language uses pitch to encode different words; apparently it isn’t, the speakers simply “abstract” the phonemic vs. phrasal pitch variations as two different things, when interpreting the sentence. Check figure 6.
And while there is a particle overtly conveying “this is a question”, ⟨吗⟩ /ma⁰/ (the “0” indicates neutral tone), it seems that you can couple it with an assertive phrasal pitch to convey rhetorical questions. And other languages (like e.g. German and English, that overtly mark questions with verb fronting) show a similar pattern.
I also found some literature claiming that it might be cross-linguistically consistent
The article also lays out some potential explanations for this. The basic gist of it is, nobody knows why but everyone has a guess.
EDIT: as another user (ABCDE) correctly pointed out, keep in mind that this works differently for open-ended vs. yes/no questions.
Thanks for providing these studies; that’s all quite fascinating