In any event, I'm baffled that a devout Catholic like you views contacting demons as BS when the Catholic church is infamously known for its legendary exorcisms.
Exorcism is not communication.
What's the point of God creating an immaterial soul that does the same thing as the brain? Why the duplication?
Not necessarily duplication but enhancement. And the process is broken we don't know exactly how it meant to be. Probably it was not meant to be any duplication in the original plan.
How are you able to distinguish what your brain does from what your immaterial soul does?
The first step is to check out the animal behaviour in other species and see differences and similarities.
Non human animals don't have immortal souls.