It’s been about 40 years since I read Julian Jayne’s book about his bicameral mind hypothesis, so my memory is more than a little fuzzy. Don’t ask me about the details! So I appreciated this summary by someone who supports the theory.

Imagine a theoretical framework that solves a long list of mysteries: the origin of religion and its concomitant features—supernatural visitations, ancestor worship, monumental mortuary architecture, divination, oracles, spirit possession, and the vestiges of archaic spirituality still visible in churches, temples, and mosques. This approach also explains otherwise inexplicable phenomena, such as hallucinations, hypnosis, glossolalia, and children’s imaginary companions. Moreover, this theoretical approach has clinical value: its argument about the originally nonpathological, adaptive nature of hallucinations helped establish an intellectual climate conducive to the Hearing Voices Network, which regards voice-hearing as a meaningful experience. Moreover, this framework comes with hypotheses waiting to be tested.

Such a framework can be found in The Origin of Consciousness in the Breakdown of the Bicameral Mind (1976) by Julian Jaynes (1920–1997). He theorized that until about three thousand years ago (with some geographic variation) humans possessed a “bicameral” (“two-chambered”) mentality in which the right hemisphere communicated with the left hemisphere using command hallucinations. These were interpreted as the voices of gods, ancestors, or godlike rulers. But population expansion and social complexity put pressure on this dual psychological system of supernatural superior and mortal subordinate. During the late second millennium BCE, this two-tier neurocultural arrangement collapsed. In response, languages—by developing metaphoric “mind words”—upgraded psychological processes. Jaynes identified the new mentality as “consciousness” (or in a wordier rendering, subjective introspectable self-awareness). Jaynesian consciousness is neither an innate, biologically fixed trait, nor something identified with sensation, thinking, or being awake. It is a learned cultural innovation.

That first paragraph claims the theory has explanatory power, but I fail to see how a hypothesis about the ancient duality of the mind explains a diverse and complex phenomenon like religion. I also don’t see the clinical value of a vague claim about hallucinations. I agree that hallucinations are real, and shouldn’t necessarily be pathologized, but where is the virtue in clinical practice to treating them as something more than a consequence of the problem of consciousness? I don’t think that splitting consciousness in two helps, because now you’ve created two equally big problems from a single problem.

You know, Wilhelm Fliess came up with an explanation of neurosis that involved a mysterious connection between the nose and the genitals, and even came up with surgical interventions to treat depression and psychosis. Did it work? No. I’m as convinced that the bicameral framework is effective in doing anything as I am about a hack chopping up turbinate bones.

The second paragraph is a silly claim about history — that there was a revolution in how the brain works 4,000 years ago, based on a hypothetical separation of mind functions before that transition, which Jaynes cannot demonstrate existed, except by his interpretation of old myths. Sure, people weren’t writing introspective psychological novels in the bronze age, but they were creating great works of art and building systems of laws and expressing themselves in poetry and music. They don’t seem fundamentally different from modern humans in that sense.

I dismissed it all as baseless fluff when I read it all those years ago, and that was before I started a research career looking at the development of cross-connections in the brains of fish and insects. The brain is full of commissures and decussations! Even your eyes split their output, with each eye sending information to both hemispheres, and the earliest neuronal pathways tend to innervate the contralateral side of the nervous system. Jaynes has to postulate that we had this massive cross-connection, but that people didn’t notice and incorporate into their ways of thinking until there was a “learned cultural innovation.”

I can well believe that there have been major cultural revolutions in our history. I just don’t see any evidence that somehow our minds were split into two chambers once upon a time.