system
A chat on subreddit /r/me_irl
human
Yeah other studies have put this closer to 70 percent with an inner monolouge and 30 percent without. 

But for sure those without are NPCs (jk)

No inner-voice seems to correlate with high extroversion, and also with low levels of education.
gpt
I'd be shocked if it's that. Honestly I thought it was like 99% of people had an inner dialogue and it was fairly rare to not have that.