Did the Bicameral Mind Evolve to Create Modern Human Consciousness?

By: Robert Lamb  | 
God speaks to Moses through a burning bush in this 15th-century German manuscript. According to the controversial theory of psychologist Julian Jaynes, every human tradition that entails prayer or divine voices is an echo of a time in which our bicameral brains simply worked that way. Historica Graphica Collection/Heritage Images/Getty Images

Key Takeaways

  • Julian Jaynes proposed that early humans operated with a "bicameral" or two-chambered mind, with one part of the brain generating commands that another part perceived as the voice of gods.
  • This theory suggests that modern consciousness, characterized by introspection and self-awareness, emerged around 3,000 years ago.
  • While Jaynes' hypothesis remains controversial and unprovable, it has prompted further research into how ancient humans experienced consciousness.

What is consciousness and how did it emerge in human beings?

Great thinkers have pondered these questions for ages – and the subject continues to intrigue us. We know that our mental state sets us apart from other animals. We also know we're a product of evolution. Gradual changes occurred over time to make us what we are today. One of those changes is the emergence of consciousness.


But when exactly did this change take place? When did humans, or perhaps our pre-human ancestors, shift from a life of instinctual existence to a life of reason, reflection and inner complexity? Furthermore, what were we like before the change? How do we imagine humans without a modern consciousness?

Various hypotheses have tackled these mind-blowing questions, entailing everything from the limitations of human attention to quantum theory. The true answer remains elusive. Today, we are going to consider a single, somewhat controversial hypothesis: the bicameral mind.


Bicameralism: What and Who

The bicameralism hypothesis was proposed by American psychologist Julian Jaynes (1920-1997) in his 1976 book "The Origin of Consciousness in the Breakdown of the Bicameral Mind." The book struck a chord with readers at the time and continues to resonate, even if many of its core ideas are ultimately unproveable.

What are those ideas? Well, much of it can be gleaned from the title itself. Jaynes proposed that modern consciousness, as we know it, emerges from the breakdown of a prior form of mentality that he dubbed the bicameral mind – or, quite literally, the mind of two houses.


Jaynes' conclusion was that, until roughly 3,000 years ago, humans were not conscious in the modern sense. He argued that modern consciousness emerged as a cultural invention in Mesopotamia, Greece. To put this in computer terms, modern consciousness was more software than hardware. This new way of thinking spread around the world, eroding and replacing the previous mental order.

And here's where the hypothesis gets even more exciting: That previous mental order, which Jaynes dubbed the bicameral mind, was a world of hallucinated voices. These voices told our ancestors what to do when we encountered novel circumstances or events. These voices, he argued, were the voices that we came to think of as the voices of the gods. In this, every human tradition that entails prayer or divine voices is an echo of a time in which our brains simply worked this way.


Bicameralism: The Unconscious Mind

So, to refresh, Jaynes argued that humans were not conscious beings before roughly 3,000 years ago. But what did he think they were? To understand this, we have to stop and consider exactly what Jaynes meant by conscious and non-conscious existence. Here's what he wrote in his 1976 book:

Consciousness is a much smaller part of our mental life than we are conscious of, because we cannot be conscious of what we are not conscious of. How simple that is to say; how difficult to appreciate! It is like asking a flashlight in a dark room to search around for something that does not have any light shining upon it. The flashlight, since there is light in what-ever direction it turns, would have to conclude that there is light everywhere. And so consciousness can seem to pervade all mentality when actually it does not.

In other words, we act non-consciously all the time – and conscious consideration of our thoughts and actions is a mere interruption to this norm. You likely behave like a kind of robot while unloading the dishwasher. You've done it thousands of times, so you're kind of on autopilot. The autopilot only "turns off" when something unexpected happens. Perhaps you break a glass, drop a fork, or catch yourself putting something in the wrong drawer.


For a bicameral human, life would be a state of autopilot – with the hallucinated voice only manifesting when something novel happened: the dropped fork, the broken glass, etc. A voice that one might interpret as a god or the spirit of an ancestor would tell us how to respond.

How would ancient civilizations have functioned like this? According to Marcel Kuijsten, Founder and Executive Director of the Julian Jaynes Society, we have to remember that people still communicated with each other – and that these societies were highly hierarchical.

"The major societal decisions and direction would have come from the great gods, which were heard by the king or the highest-ranking priests," Kuijsten says in an email interview. "These commands would then be communicated down the hierarchy verbally, just as they would be today. The voices that most individuals heard would have pertained to their own day-to-day lives. If they did hear voices regarding larger issues, it's unlikely that anyone above them in the hierarchy would have listened to them."


Bicameralism: The Split Brain

Now, as interesting as this concept is, you might well wonder how all of this ties together into a hypothesis about the origins of consciousness. What is this bicameral voice anyway and why would it be experienced as an auditory hallucination?

Jaynes argued that the brains of bicameral humans used language to convey experience from the right to the left hemisphere.


As explored in the work of neuroscientists Roger Sperry and Michael Gazzaniga in the 1960s and 70s, the two hemispheres of the brain are quite divided and can act independently, almost as if they are two separate individuals. They explored this via the separation of animal brain hemispheres and by studying humans who had undergone a corpus callosotomy to treat severe epilepsy. Via this surgical procedure, the part of the brain known as the corpus callosum, which connects the two hemispheres and allows communication between them, is severed.

While the patients seemingly felt mentally whole afterward, laboratory experiments revealed the subtle ways in which the hemispheres worked independently. This led Gazzaniga to formulate his left-brain interpreter theory, in which the language-centered left hemisphere generates a kind of story explaining why the non-dominate right hemisphere did something. He argued that our sense of self emerges out of this "interpretation."

Gazzaniga's theory concerned the modern human condition, while Jaynes thought that the brain used language to convey experience from one hemisphere to another in ancient humans – what we would today call an auditory hallucination.

Gazzaniga's left-brain interpreter theory, in which the language-centered left hemisphere generates a kind of story explaining why the non-dominate right hemisphere did something, posited that our sense of self emerges out of this "interpretation."

Kuijsten points to studies of modern voice-hearers that show that they often experience what are called "command hallucinations" that direct their behavior, very much like what Jaynes documents in the ancient world. Additionally, while Jaynes died in 1997, subsequent neuroscientific findings strike Kuijsten as supportive.

"By 1999, brain imaging technology had progressed to the point that a study was done that imaged the brain of someone at the exact moment that they were hallucinating," Kuijsten says. "It showed the right/left temporal lobe interaction during auditory verbal hallucinations that Jaynes's neurological model predicted. Since then, this finding has been confirmed by dozens of other studies."

So what, according to Jaynes, changed beginning roughly 3,000 years ago?


Bicameralism: Metaphorical Breakdown

Jaynes argued that the breakdown of the bicameral mind would have stemmed from the use of metaphors. Modern consciousness, he wrote, is a metaphor-based model of reality, based on the way we use language to create metaphors. As this way of speaking and thinking spread again, like software rather than evolved hardware – it would have disrupted the way humans thought.

Jaynes spends a great deal of time in his work drawing evidence for his hypothesis via ancient writings, art, music and architecture – such as divine statues that were, in various traditions, said to on occasion speak to mortals. This would have been the fading bicameral voice coaxed from the recesses of the mind and interpreted as the words of a god.


As for Kuijsten, he is particularly intrigued by the idea of bicameral dreams. "Most people assume that dreams were basically the same in the ancient world as they are today, but surprisingly this is not the case," Kuijsten says. "Dreams in the ancient world were generally what's called 'visitation dreams' – or what we might call 'bicameral dreams.' In these types of dreams, the person experiences themselves asleep in their bed, and they are then visited by a god or dead ancestor that gives them advice or a command. So in the ancient world, the dream experience very much parallels the waking bicameral experience." As consciousness developed, the nature of the dream itself changed.

Bicameralism: Is it True?

The work of Julian Jaynes continues to fascinate readers, but it remains controversial when it comes to scholarly consideration of human consciousness. While he has his fervent supporters, there is much to the hypothesis that cannot be studied in a scientifically verifiable way. As such, it would seem a hypothesis destined to never advance to the theory stage. Jaynes' interpretations of ancient cultures remain just that: interpretations.

Jaynes himself admitted that he focused his work on the cultures and languages that were best known to him. For instance, while he found evidence for bicameralism in Greek culture, he left Chinese culture largely unexplored. Other scholars, such as Sinologist Michael Carr and Tibetologist Todd Gibson, have continued to explore and advance the hypothesis, and have documented evidence for bicameralism in places like China and Tibet.


"While it certainly remains controversial and outside of mainstream psychology, over the years I have seen a gradual increase in interest and acceptance," Kuijsten says. "There is a certain risk for people in academia to be seen as embracing new or controversial ideas, but the more new material we've published on Jaynes's theory – and the more we've cleared up misconceptions – the more we've made it easier for others to openly support it."

More Work to be Done

Some commentators have suggested that there may be some truth in Jaynes' work, but that the reality might be more complicated. The transition to modern consciousness, according to philosopher and cognitive scientist Daniel Dennett, may have been less drastic and entailed multiple features. Kuijsten, however, stresses that Jaynes never claimed to have all the answers, and that he ultimately laid a foundation for others to build upon – much like Darwin's theory of evolution.

"I think generally speaking Jaynes's hypothesis is correct – in my view, the overall pattern of evidence is just too compelling," Kuijsten says. "And there are too many things that would otherwise remain inexplicable."


Still, Kuijsten stresses that more work needs to be done. "We could learn a great deal by reexamining ancient civilizations and retranslating ancient texts through the lens of Jaynes's theory," he says. "For example, I think the transition from bicamerality to consciousness could be much better understood. Exactly when did it occur in various cultures? How long was the transition? Did the different features of consciousness emerge gradually, and did different features emerge differently in different cultures?"

The study and contemplation of consciousness continues, and perhaps one day we'll have a theory that meets the criteria of consensus science. Until then, humans will continue to gaze back on the past and wonder what came before modern consciousness.

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Frequently Asked Questions

How does the bicameral mind theory explain ancient art and architecture?
The bicameral mind theory suggests that ancient art and architecture, such as statues believed to speak to mortals, reflect a time when people experienced hallucinated voices as commands from gods, integral to societal decision-making.
Has modern neuroscience found evidence supporting the bicameral mind theory?
Some modern neuroscience studies, particularly on auditory verbal hallucinations, have shown brain activity patterns that align with Jaynes's predictions.