One could make the argument that higher-level thought is not the same as awareness of higher-level thought; perhaps language only affords the latter.

It's clear humans have several networks working together. Some Mathematicians report they 'see' the solution, these rely on a visual network *. Others report they prefer to do math symbolically (relying on the language network?).

Perhaps there are also multiple human paths to higher-level thought, with Keller (who lost her sight) using the language facility while others don't have to.

* Given Box 1 contents, the article authors seem unaware of the research on this? e.g.

https://www.youcubed.org/resource/visual-mathematics/

https://www.hilarispublisher.com/open-access/seeing-as-under...

She learned "language" later than most. The primary function for her was as communication with the outside world, not for cognition, which she was already doing from birth.

Keller's early experience of the world differed from typical in dimensions beyond language recognition.