Maybe not exactly the same thing you were talking about, but did you see this in the Guardian today?

https://www.theguardian.com/books/2020/apr/27/majority-of-authors-hear-their-characters-speak-finds-study?CMP=Share_AndroidApp_Slack

The study has more to do with writing fiction, but I find it to be true. When I write fictional stories, my characters definitely take on voices and agency of their own.

I think to a certain extent that crosses over into non-fiction, that ability to tap into an inner life, to plumb depths of experience and write from the inside out.