I had a strange coincidence today. I was in a newsagents, looking at magazines and, I found a magazine with an article which discusses Julian Jaynes' ideas on the bicameral mind. The article is in 'New Statesman' (26 March- 15 April 2021).It is called, 'The voice in your head', by Sophie McBain. It discusses a psychiatrist, Maurius Romme, who took a particular interest in the work of Jaynes. He had used it as a basis for aiding people who hear voices. Romme was interested in the work of Charles Fernyhough, who focused on the way in which thoughts are processed as inner speech and the role of trauma, which can lead to dissociation of consciousness.
Romme worked with a particular woman, Patsy Hage, a voice hearer, who contributed to Romme's writing. The writer of the article summarises how Patsy Hage,
'found it remarkable how similar the gods were to the voices she heard. They dispensed threats and orders, they bullied and mocked, they provided comfort and advice. The gods were always obeyed, just as she and other voice-hearers often obeyed their voices, finding it hard to know where the voices ended and their true selves began. "We voice-hearers are probably living in the wrong era," she concluded.
Apart from the article, I think another area relevant to your discussion is the way in which hallucinogenics can trigger voices. When I experimented on cannabis biscuits and Lsd at a warehouse rave, I experience voices. I was worrying about all the work I had to do on the course I was doing and I began hearing voices, telling me, ' Its a very life' repeatedly and, also, when I kept hearing voices saying, 'He's eaten skunk cake'. I was not sure if the voices were probably in my head or external, because
boundaries seemed unclear. Perhaps, hallucinogenics trigger a throwback to a bicameral mental state.