Up to about the 19th century, poltergeists were routinely blamed on the Devil, demons, witches, and the ghosts of the dead. In more modern timesm, poltergeists are widely believed to be an involuntary or unconscious type of psychkinesis (PK) on the part of the living, the so-called "agent". The agent is believed to exercise unconscious thought processes that produce the disturbance.
Physical assaults - bitings, spittings, pinchings, punchings, and sexual molestations - continue to be reported in a small percentage of cases.
