The talk of the meme-o-sphere recently has been on NPCs (non-player characters), not in video games, but in real life. Originally, "NPC" arose as a term of abuse approximating "normie" or "brainlet", but there have been some who are realizing that it might have more truth to it than anticipated.
For a while now, a post from le Reddit has been circulating from a somewhat disturbed user divulged that he only recently began thinking in language, saying that his life before "mindless" and "soul-less" and described himself as "barely even conscious". One might also be reminded of the quip of James Huneker on Chopin's Étude Op. 25, Num. 11 (better known nowadays by being quoted by Douglass Hofstadter in Gödel, Escher, Bach) that "small-souled men, no matter how agile their fingers, should avoid it". Of course, listeners of the biggest-braned podcast Not Related! will remember in the episode on the Bicameral Mind, we talked on Julian Jaynes's theory of consciousness, in which consciousness is not something inherent to our biological inventory, but a kind of mental habit we develop, partially based on the metaphors of language and our need in society. Different societies and cultures are liable to create different levels of consciousness in people.
There seems to be circumstantial evidence everywhere that the internal worlds of others just are not quite the same as ours. There's a huge scientific and epistemological problem though: how can we empirically and objectively verify the nature consciousness, an aspect of mental life which is by its nature accessible only subjectively?
I dont think this question is answerable in the scientific mindset we currently have. More interesting as a hint would be a deeper understanding, albeit indirect of what other people's inner worlds are like. I'm sort of curious to hear what your inner life is like, and how you experience "thinking" if it's something unique.
I'll do my part and share with others my mental life. I do have internal speech and am not an NPC and am indeed conscious. My internal speech is a little bit different from how I hear others describe theirs. Sometimes, usually when I'm thinking very slowly and deliberately, I think at only slightly faster than enunciated English in real life. Most of the time, the "speech" is quite different: the best way I can describe the experience is as if you "hummed" the intonation of English to yourself without opening your mouth (this is not something I literally do, but how I experience it in my head). This mild humming occurs at a speed significantly faster than normal speech and though it provokes the same "meaning" and cognitive scaffolding as language does. It's not an annoying or abrasive humming, I should say: it's more like if someone is gently (though quickly) talking in the other room. This hummed speech "feels" like English, but when I slow it down because it just gave me a great idea that I want to write down, I realize that there sometimes aren't actually English words or English syntax that directly capture what I was thinking.
I should say, when I say that it "feels" like English, I mean that, as someone who knows a lot of different languages and has an intuitive grasp of etymology, I have distinct, almost synesthetic feelings that correspond to words of different origins. When I experience what linguists call "tip of the tongue phenomena" (when you forgot a word but can remember what it means and how it starts), I also can recall the approximate etymology. What I mean is that this humming speech has the same feeling as English words do.
I'd probably say that most of my mental time does not use this kind of internal speech. It's not that I'm unconscious, but because I usually think about more abstract and non-linear things with interlocking, organic shapes. This is a little closer to how some savants describe their mental life, but I suspect it's a lot more common than that, not just because I have it, but it seems to be the kind of thing that people would take for granted. The typical description is that invisible shapes of different "meanings" come together and connect, or hydraulic organic machinery interacts in such a way to give you the correct answers to math problems or some advanced mental decision whose actual mechanism is opaque to you. The thing is, while I experience this, it's something I'm only an observer of, and while I say that the shapes have "meanings", that's sort of my assumption, because if you could display my cognitive theater on a screen, I couldn't point out what is what with my conscious mind. I think this is some kind of felt vision into the structure of intuition more than anything else.
As a minor detail, I also have no cognitive "me". Or at least not unless I want one. What I mean by that is that people will often describe themselves in their imaginations as seeing in the first person, or seeing themselves in third person (as if watching themselves on TV). These are sometimes called the "I" and "me". I can easily imagine myself, say, taking a walk and seeing myself walking from above, but that's not something I regularly do without prodding. Whenever I imagine myself doing something, I see everything from my own eyes unless deliberately trying to do otherwise.
Anyway, in the future, as I read more of the literature, I might be interested in doing an episode on "NPC" and people's inner lifes. If you have a mental life that is notable or distinct, feel free to email me a brief explanation. I'm curious to see what's out there.