Isolation tanks have been reported to cause hallucinations in some individuals. One theory is that in the absence of sensory input, the brain makes shit up.
Why don’t blind or deaf people have hallucinations?
Just a guess, but people have hallucinations in that scenario because regions of the brain are starved from the input they expect. For deaf or blind people those processing areas of the brain have already atrophied or been reassigned.
People who are going blind can hallucinate:
I’ve had audio hallucinations. I can’t hear most normal volume sounds and wear hearing aids. Sometimes, usually in the evening after I remove my hearing aids, I will hear voices. They sound like the television is playing. It sounds like voices mumbling but I don’t get any understandable words. I’ve got up to check and see if the TV has turned itself on several times.
Profound hearing loss here.
Not real often, but I have heard things that I know aren’t real. My weirdest (more than once) thing I’ve heard was the sound of a tricycle bell ringing in the distance and very softly. Like ring ring ring ring, then again about 20 minutes later. The first time I heard that it was about 5 o’clock in the afternoon outside, same day, but again at 10 pm inside of my house. It’s been awhile since I’ve heard the ring ring.
PSA.
When a deaf person doesn’t understand what you’re saying, and ask you to repeat what you said, talking in a louder voice doesn’t help. Try Face to face while talking slower.
Related thread I posted a few years ago:
This times a thousand.