> we literally don't have the language to figure out how other people perceive things.
you are right, talking about mental processes is difficult.
Nobody knows how exactly other person perceive things, there is no objective way to measure things out.
(Offtopic: describing smell is also difficult)
In this thread, we see that rudimentary language for it exists.
For example: lot of people use sentence like “to hear my own thoughts” and a lot of people understand that fine.