This is fascinating to me, and it makes me wonder if the presence of these voices can in some ways be beneficial to people living in cultures in which they have more positive messages. This also brings to mind a certain Terence McKenna talk in which he discusses schizophrenia and how it might be useful to cultures in which shamanism is practiced. How much is mental illness due to biomechanical malfunctioning of the brain, and how much does it arise due to an inability of certain personality types to function in a society that simply isn't designed to accommodate their existence? I'm curious if it'll ever be possible to draw a clear line here.