In psychology, bicameralism is a 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 his 1976 book The Origin of Consciousness in the Breakdown of the Bicameral Mind, wherein he made the case that a bicameral mentality, that is to say a mental state in which there are two distinct sections of consciousness, was the normal and ubiquitous state of the human mind as recently as 3000 years ago. He used governmental bicameralism to metaphorically describe such a state, in which the experiences and memories of the right hemisphere of the brain are transmitted to the left hemisphere via auditory hallucinations. This mental model was replaced by the conscious mode of thought, which Jaynes argues is grounded in the acquisition of metaphorical language. The idea that language is a necessary component of subjective consciousness and more abstract forms of thinking has been gaining acceptance in recent years, with proponents such as Daniel Dennett, William H. Calvin, Merlin Donald, John Limber, Howard Margolis, Peter Carruthers, and Jose Luis Bermudez.