Bicameralism (psychology)
In psychology, bicameralism is a controversial hypothesis which argues that the human brain once assumed a state known as a bicameral mind in which cognitive functions are divided between one part of the brain which appears to be "speaking," and a second part which listens and obeys.
The term was coined by psychologist Julian Jaynes, who presented the idea in the 1976 book The Origin of Consciousness in the Breakdown of the Bicameral Mind, wherein he made the case that the bicameral mentality was the normal state of the human mind everywhere as recently as 3000 years ago. He used governmental bicameralism metaphorically to describe this state, where the stored up experience of the right hemisphere was transmitted to the left hemisphere via auditory hallucinations. This mental model was replaced by the conscious mode of thought, which Jaynes argues is based on metaphorical language. The idea that language is necessary for subjective consciousness or higher forms of thought has been gaining in acceptance in recent years, with proponents such as Daniel Dennett, William Calvin, Merlin Donald, John Limber, Howard Margolis, and Jose Luis Bermudez.

# The case for bicameralism
According to Jaynes, ancient people in the bicameral state would function in a manner similar to that of a modern-day 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 these voices without question. Others have argued that this state of mind is recreated in members of cults.
In his 1976 work The Origin of Consciousness in the Breakdown of the Bicameral Mind, Julian Jaynes proposed that human brains existed in a bicameral state until as recently as 3000 years ago. Jaynes builds a case for this hypothesis by citing evidence from many diverse sources including historical literature. He took an interdisciplinary approach, drawing data from many different fields.
Jaynes asserts 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, Jaynes argued that the bicameral individual was guided by mental commands believed to be issued by external "gods"the commands which were so often recorded in ancient myths, legends and historical accounts; these commands were however emanating from individuals' own minds. This is exemplified not only in the commands given to characters in ancient epics but also the very muses of Greek mythology which "sang" the poems: Jaynes argues that while later interpretations see the muses as a simple personification of creative inspiration, the ancients literally heard muses as the direct source of their music and poetry.
Jaynes inferred that these "voices" came from the right brain counterparts of the left brain language centresspecifically, the counterparts to Wernicke's area and Broca's area. These regions are somewhat dormant in the right brains of most modern humans, but Jaynes noted that some studies show that auditory hallucinations correspond to increased activity in these areas of the brain.
For example, he asserts that, in The Iliad and sections of the Old Testament in The Bible, no mention is made of any kind of cognitive processes such as introspection, and he argues that there is no apparent indication that the writers were self-aware. According to Jaynes, the older portions of the Old Testament (such as the Book of Amos) have little or none of the features of some later books of the Old Testament (such as Ecclesiastes) as well as later works such as The Odyssey, which show indications of a profoundly different kind of mentalityan early form of consciousness.
Jaynes noted that in ancient societies, the corpses of the dead were often treated as though they were still alive (being seated on chairs, dressed in clothing, and even fed food) and he argued that the dead bodies were presumed to be still living and the source of auditory hallucinations (see ancestor worship). This adaptation to the village communities of 100 individuals or more formed the core of religion.  Unlike today's hallucinations, the voices of ancient times were structured by cultural norms to produce a seamlessly functioning society.
In ancient times, Jaynes noted, gods were generally much more numerous and much more anthropomorphic than in modern times, and speculates that this was because each bicameral person had their own "god" who reflected their own desires and experiences.
Even in modern times, Jaynes notes that there is no consensus as to the cause or origins of schizophrenia (the subject is still hotly debated). According to Jaynes, schizophrenia is simply a vestige of humanity's earlier state. Recent evidence shows that many schizophrenics don't just hear random voices but experience "command hallucinations" instructing their behavior or urging them to commit certain acts. As support for Jaynes's argument, these command hallucinations are little different from the commands from gods which feature so prominently in ancient stories. Indirect evidence supporting Jaynes's theory that hallucinations once played an important role in human mentality can be found in the recent book Muses, Madmen, and Prophets: Rethinking the History, Science, and Meaning of Auditory Hallucination by Daniel Smith.

## Breakdown of bicameralism
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 second millennium BC. He speculates that primitive ancient societies tended to collapse periodically (as in Egypt's Old Kingdom and the periodically vanishing cities of the Mayas) due to increased societal complexity that could not be sustained by this bicameral mindset. The mass migrations of the second millennium BC created a rash of unexpected situations and stresses that required ancient minds to become more flexible and creative. Self-awareness, or consciousness, was the culturally evolved solution to this problem. Thus cultural necessity (that of interacting with migrating tribes, or surviving as a member of such) forced humanity to become self-aware or perish. Thus consciousness, like bicamerality, emerged as a neurological adaptation to social complexity.
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. The consultation of special bicamerally operative individuals, or of casting lots and so forth, was a response to this loss, a transitional era depicted for example in the book of 1 Samuel. It was also evidenced in children who could communicate with the gods, but as their neurology was set by language and society they gradually lost that ability. Those who continued prophesying, being bicameral according to Jaynes, could be killed.
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.

## Responses
Jaynes's hypothesis lacked discussion by mainstream academics. This can be attributed to four primary reasons:
- The broad nature of the theory, with many feeling unqualified to comment on aspects of the theory that fell outside of their area of expertise,
- Many simply pre-judged Jaynes's ideas on consciousness without actually reading his theory; in other words, they judged Jaynes's ideas on a recent development of consciousness based on their own more broad (and some would say incorrect) understanding of the term consciousness, not Jaynes's more precise definition. Others read his discussion of consciousness but clearly still misunderstood it.
- A certain amount of dogmatism exists in academia  and especially in psychology  such that advocating controversial ideas is often difficult for those purusing tenure at a major university.
- Many informed, open-minded scientists considered Jayne's hypothesis to lack sufficient confirmatory evidence to warrant further investigation.
His proposals generated great controversy when first published, and provided impetus for many other scientists and philosophers to investigate the matters it discussed in detail in order to attempt to refute its arguments
Some theorists, such as the philosopher Daniel Dennett, consider bicameralism to be quite intriguing but probably incorrect in some aspects. In a 1987 letter to the American Journal of Psychiatry, Dr. H. Steven Moffic questioned why Jaynes's theory was left out of a discussion on auditory hallucinations by Drs. Assad and Shapiro. In response, Drs. Assad and Shapiro wrote, "...Jaynes' hypothesis makes for interesting reading and stimulates much thought in the receptive reader. It does not, however, adequately explain one of the central mysteries of madness: hallucination." However, Drs. Assad and Shapiro's comment that there is no evidence for involvement of the right temporal lobe in auditory hallucination was incorrect even at that time. A number of more recent studies provide additional evidence to right hemisphere involvement in auditory hallucinations.
Recent neuroimaging studies provide new evidence for Jaynes's neurological model, i.e. auditory hallucinations arising in the right temporal-parietal lobe and being transmitted to the left temporal-parietal lobe. This was pointed out by Dr. Robert Olin in Lancet and Dr. Leo Sher in the Journal of Psychiatry and Neuroscience, and further discussed in the book Reflections on the Dawn of Consciousness.
Another proponent of Jaynes's theory is Gregory Cochran, adjunct professor of anthropology at the University of Utah and an expert in genetics and human evolution. Cochran writes: "Genes affecting personality, reproductive strategies, cognition, are all able to change significantly over few-millennia time scales if the environment favors such change  and this includes the new environments we have made for ourselves, things like new ways of making a living and new social structures. ... There is evidence that such change has occurred. ... On first reading, Breakdown seemed one of the craziest books ever written, but Jaynes may have been on to something."  Author and historian of science Morris Berman writes, " description of this new consciousness is one of the best I have come across." Danish science writer Tor Nrretranders discusses Jaynes's theory favorably in his book The User Illusion: Cutting Consciousness Down to Size.
Some argue that Jaynes's recent dating of the development of consciousness is contradicted by cave paintings that are 30,000 or more years old. Mainstream theorists often cite cave art as evidence for the emergence of the modern mind. However, recent discussion by psychologist Nicholas Humphrey of an autistic child named Nadia who was capable of cave-art like drawings at the age of 3 calls this into question.
Evidence taken to contradict Jaynes's proposed date of the transition from bicameralism is the Gilgamesh Epic: although the story of Gilgamesh was recorded centuries before the Old Testament, and though its setting is contemporaneous or earlier than the Old Testament stories, the Gilgamesh story describes such features as introspection. Jaynes himself, noting that the most complete version of the Gilgamesh epic dates to post-bicameral times (7th century BC), dismisses these instances of introspection as the result of rewriting and expansion by later conscious scribes, and points to differences between the more recent version of Gilgamesh and surviving fragments of earlier versions. ("The most interesting comparison is in Tablet X." - detailed in The Origin of Consciousness, 1982 edition, p. 252f.) Others, such as science fiction author Neal Stephenson, have since conjectured that heroic epics and myths may be rooted in isolated individuals who became self-aware early and could accordingly outmatch and manipulate their fellows.
Richard Dawkins discusses Jaynes's theory in his recent book The God Delusion. In his chapter on the roots of religion, Dawkins writes: "It is one of those books that is either complete rubbish or a work of consummate genius, nothing in between!"
Many others consider Jaynes's hypothesis worthy and offer conditional support, arguing the notion deserves further study. Some scholars suggest that the hypothesis describes a real event, but that Jaynes provides the wrong date. One hypothesis about pre-historic cave paintings, for example, is that they offer us a window into a time when consciousness was emerging, perhaps through the breakdown of bicameralism.
A collection of Jaynes's essays on bicameralism combined with those of contemporary scholars was published in 2007, in a book entitled Reflections on the Dawn of Consciousness: Julian Jaynes's Bicameral Mind Theory Revisited. Included in this book is new support for Jaynes's theory by Marcel Kuijsten, psychological anthropologist Brian J. McVeigh, psychologists John Limber and Scott Greer, clinical psychologist John Hamilton, philosophers Jan Sleutels and David Stove, and an expert in ancient Chinese customs and linguistics, Michael Carr. The book also contains an extensive biography of Julian Jaynes by historian of psychology William Woodward and June Tower, and a Foreword by neuroscientist Michael J. Persinger.
Additional essays on Jaynes's theory can be found in The Jaynesian, the newsletter of the Julian Jaynes Society.

## Similar ideas
The neuroscientist Michael Persinger studies the role of the right temporal lobe in the feeling of a sensed presence and god beliefs. The neuroscientist V.S. Ramachandran discusses cases of hyper religiousity in patients with temporal lobe epilepsy. Other theorists have also made the claim that consciousness is a social construction, including Lev Vygotsky, Rom Harre, and George Herbert Mead. Cognitive psychologist David R. Olson has written on the impact of reading and writing to cognition and the mind.  Lloyd deMause and the  psychohistorians have advanced a model that aims to understand the ubiquity of the schizoid personality in the Old World. The main difference between psychohistorians and Julian Jaynes is that psychohistorians focus on childrearing modes as the main cause of the schizoid personality.

# Bicameralism in popular culture
The ideas set forth in Jaynes' book have been great fodder for cyberpunk authors; Neal Stephenson's first several books (The Big U, Zodiac, Snow Crash) involve the bicameral mind theory, as does Bruce Sterling's Distraction. The book has been highly influential in a neo-objectivist philosophy called Neo-Tech. Jaynes' hypothesis is referenced, at least in passing, in the cyberpunk comic Transmetropolitan.
Bicameralism is central to the plot of Sebastian Faulks' novel Human Traces, and is referred to in the novel's appendices. The Origin of Consciousness in the Breakdown of the Bicameral Mind plays a role in Paul Levinson's 2002 novel The Consciousness Plague, appears in the Recommended Reading section of Robert J. Sawyer's 2005 novel Mindscan, and was mentioned as reading material by Leopold Cain, shortly before his kidnap in NBC-TV's Kidnapped, in the September 2006 premier broadcast of the series. The Beast, Henry McCoy, can be seen reading a copy of The Origin in issue 134 of the Uncanny X-men, during the heart of what was to become known as The Dark Phoenix Saga.  In 50 Degrees Below, one of Kim Stanley Robinson's characters states that they don't play disc golf, but rather "the gods play through us," and another character describes him as being "pre-breakdown of the bicameral mind." Bicameralism is also briefly mentioned in From Hell by Alan Moore as well as American Gods by Neil Gaiman, although it is never refered to by name in either work (although Moore's lengthy annotations to Fromm Hell do specifically credit Jaynes' book).
"Your Bicameral Mind... Mind Your Bicameral." is etched into onto the 7" vinyl pressing of David Bowie's 1979 single, 'Boys Keep Swinging'.

# Editions
The Origin of Consciousness was financially successful, and has been reprinted several times. The book was originally published in 1976 (ISBN 0-395-20729-0) and was nominated for the National Book Award in 1978.  It has since been reissued (ISBN 0-618-05707-2). A new edition, with an afterword that addressed some criticisms and restated the main themes, was published in the US in 1990. This version was published in the UK by Penguin Books in 1993 (ISBN 0-14-017491-5). It has been translated into Italian, Spanish, German, and French.

# Critical quotations
- If we are going to use this top-down approach, we are going to have to be bold. We are going to have to be speculative, but there is good and bad speculation, and this is not an unparalleled activity in science.  Those scientists who have no taste for this sort of speculative enterprise will just have to stay in the trenches and do without it, while the rest of us risk embarrassing mistakes and have a lot of fun.