So obviously we all know how the placebo effect can make people perceive what they are hearing differently, and that it actually does not alter the real frequency response of the person's ear.
Now what I would like to know, is how mood, or perhaps certain hormones might affect that same perception. This question came to mind when I was researching hyperacusis, which is basically hypersensitivity to sound. This also led to another google of seratonin, which some say affect our hearing.
Additionally, I heard, but have not found through google, that some aes panelist did some experiments that produced results where patients were able to hear things louder than two weeks before. To me, that is very interesting, as it implies we are able to change how we hear things at a fundamental level.
I don't know much in the way psychoacoustics, nor do I know how I could learn more of it, which is why I'm asking now, but I think it would be in the interest of all of us (much more than we think) if we could somehow improve sound quality not just through the building of better equipment.