Dr. J. Allan Hobson, a psychiatrist and sleep researcher at Harvard, argues that dreaming is a parallel state of consciousness that is continually running but normally suppressed during waking. This is supported by research on lucid dreaming, which has been found to have elements of both rapid-eye-movement (REM) sleep and of waking.

Hobson argues that the main function of REM, when most dreaming occurs, is physiological: the brain is warming its circuits, anticipating the sights and sounds and emotions of waking.

He also suggests that the flights of imagination in schizophrenia may be related to an abnormal activation of a dreaming consciousness.