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.