A little unrelated, but I remember hearing that going up at the end of a sentence when talking to a baby (doing a baby voice) is almost universal, but there’s one or two places on earth where that’s who you talk to people who are extremely senior or important. I think the one example cited was an island nation without much contact with the wider world.

Here’s a source (I think without the counter example): https://www.npr.org/2022/07/23/1113206642/baby-talk-parenting-language-research