zlacker

A concept in every human culture - i.e., created in every culture, not passed from one to some others - is mentalese [0]: "A universal non-verbal system of concepts, etc., conceived of as an innate representational system resembling language, which is the medium of thought and underlies the ability to learn and use a language." [1]

If you look up 'mentalese' you can find a bunch written about it. There's an in-depth article by Daniel Gregory and Peter Langland-Hassan, in the incredible Stanford Encyclopedia of Philosophy, on Inner Speech (admittedly, I'm taking a leap to think they mean precisely the same thing). [2]

[0] Steven Pinker, The Blank Slate: The Modern Denial of Human Nature (2002)

[1] Oxford English Dictionary

[2] https://plato.stanford.edu/entries/inner-speech/