Not sure if nonverbal is the right word for it, but those that who think not as if they’re speaking in their mind, through some other ways like imagery, feelings, or however.
Often the conscience is described as a little voice in one’s mind saying what’s right/wrong to do, but for those that who think differently, how’s that experienced? Good/bad imagery or feelings instead?
Humans very easily process language. If they know a language, I think they’ll have some sort of ‘internal monologue’. Also, pop culture promotes a conscience in that sense. So, I think anyone who’s fluent with a language would probably talk to themselves, and that’s what a bunch of their ‘conscience’ would look like.
But for humans without language, we still have brain areas for processing pleasure, danger, ‘gut feelings’. Like humans with language, their behaviour/conscience would probably be shaped by what’s worked and what not worked in the past, as well as survival instincts. But it’d be more emotional or physical than talking to oneself. That’s my two cents anyway!
Fwiw it’s not so much without a language as it is there are some people who think without an internal monologue from what I’ve read here & there. They can speak and write in a language no problem, but their primary mode of thought is different.
I don’t know all the different forms that may take, nor how prevalent it is, only that it’s not unheard of.