Doppelgänger

"Arzy and his colleagues suggest that the left temporoparietal junction of the brain evokes the sensation of self image—body location, position, posture etc. When the left temporoparietal junction is disturbed, the sensation of self-attribution is broken and may be replaced by the sensation of a foreign presence or copy of oneself displaced nearby. This copy mirrors the real person's body posture, location and position. Arzy and his colleagues suggest that the phenomenon they created is seen in certain mental illnesses, such as schizophrenia, particularly when accompanied by paranoia, delusions of persecution and of alien control. Nevertheless, the effects reported are highly reminiscent of the doppelgänger phenomenon. Accordingly, some reports of doppelgängers may well be due to failure of the left temporoparietal junction."