"The bicameral mentality would be non-conscious in its inability to reason and articulate about mental contents through meta-reflection, reacting without explicitly realizing and without the meta-reflective ability to give an account of why one did so. The bicameral mind would thus lack metaconsciousness, autobiographical memory and the capacity for executive "ego functions" such as deliberate mind-wandering and conscious introspection of mental content. When bicamerality as a method of social control was no longer adaptive in complex civilizations, this mental model was replaced by the conscious mode of thought which, Jaynes argued, is grounded in the acquisition of metaphorical language learned by exposure to narrative practice.
According to Jaynes, ancient people in the bicameral state of mind would have experienced the world in a manner that has some similarities to that of a schizophrenic. Rather than making conscious evaluations in novel or unexpected situations, the person would hallucinate a voice or "god" giving admonitory advice or commands and obey without question: one would not be at all conscious of one's own thought processes per se."
"Jaynes asserted that, until roughly the times written about in Homer's Iliad, humans did not generally have the self-awareness characteristic of consciousness as most people experience it today. Rather, the bicameral individual was guided by mental commands believed to be issued by external "gods" — commands which were recorded in ancient myths, legends and historical accounts."
"According to Jaynes, in the Iliad and sections of the Old Testament no mention is made of any kind of cognitive processes such as introspection, and there is no apparent indication that the writers were self-aware. Jaynes suggests, the older portions of the Old Testament (such as the Book of Amos) have few or none of the features of some later books of the Old Testament (such as Ecclesiastes) as well as later works such as Homer's Odyssey, which show indications of a profoundly different kind of mentality — an early form of consciousness."
"Jaynes notes that even in modern times there is no consensus as to the cause or origins of schizophrenia. Jaynes argues that schizophrenia is a vestige of humanity's earlier bicameral state."
"Jaynes theorized that a shift from bicameralism marked the beginning of introspection and consciousness as we know it today. According to Jaynes, this bicameral mentality began malfunctioning or "breaking down" during the 2nd millennium BCE. He speculates that primitive ancient societies tended to collapse periodically (e.g., Egypt's Intermediate Periods, as well as the periodically vanishing cities of the Mayas) as changes in the environment strained the socio-cultural equilibria sustained by this bicameral mindset. The Bronze age collapse of the 2nd millennium BCE led to mass migrations and created a rash of unexpected situations and stresses which required ancient minds to become more flexible and creative. Self-awareness, or consciousness, was the culturally evolved solution to this problem. This necessity of communicating commonly observed phenomena among individuals who shared no common language or cultural upbringing encouraged those communities to become self-aware to survive in a new environment. Thus consciousness, like bicamerality, emerged as a neurological adaptation to social complexity in a changing world.
Jaynes further argues that divination, prayer, and oracles arose during this breakdown period, in an attempt to summon instructions from the "gods" whose voices could no longer be heard. [..] Leftovers of the bicameral mind today, according to Jaynes, include religion, hypnosis, possession, schizophrenia, and the general sense of need for external authority in decision-making"