Quote:
The important question to me being: "Are all modern manifestations of hallucinations vestiges of the bicameral mind?"
For Julian Jaynes evolution was extremely important. It is an important aspect of evolution - i.e., a law of evolution - that all attributes and characteristics of the ancesters are inherited by the newly evolved kind.
When J.J. explains what he means with "consciousness" he first of all emphasizes what is NOT consciousness. And by doing so he only refers to examples of abilities of the modern mind and all those examples belong to the abilities of the subconscious mind (or subconscious soul or subconscious psyche). Implicitly he says therefore: yes, our subconscious soul is alive and active or else we wouldn't be able to play piano.
In my understanding of J.J. I assume that the subconscious mind is identical with the bicameral mind. We have all the abilities of pre-conscious, bicameral beings with the only exception: we have in addition consciousness.
I think the problem with understanding J.J. lies mostly in our inability to become aware that most of our mental abilities are executed by our sunconscious mind. Our consciousness corresponds with our subconscious mind by sending a task and receiving a result. Our conscious mind fights very hard to admit the process between task and result. This process is executed by our subconscious mind.
Back to your question: hallucinated voices are very dramatic vestiges, indicators for the fact that the bicameral mind is active and alive in us modern beings. But they might indicate that the "normal" correspondence between conscious and subconscious mind is somewhat disturbed. Another way to look at this phenomenon: it shows us that the subconscious sole finds a way to make herself heard when she is otherwise - maybe - suppressed. With this "suppression" I mean that the circumstances of life might be such that the consciousness is unable to receive the message. If there is a block of any sort for consciousness to receive this life-protecting message the subconscious soul refers back to the pre-conscious way.
It could be that people who hear voices are afraid of their own subconscious soul and their consciousness suppresses the messages from this unknown area with abstract despotism, caused by anxieties. Therefore, the subconscious soul makes herself to be heard the very old way to reach the conscious mind.
This is just a theory, a speculation.