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A chicken can be hypnotized, or put into a trance, with its head down near the ground, by drawing a line along the ground with a stick or a finger, starting at the beak and extending straight outward in front of the chicken. If the chicken is hypnotized in this manner, it will continue to stare at the line, remaining immobile for as long as 30 minutes. Other methods of inducing this state are also known. Ethologists refer to this state as 'tonic immobility' i.e. a natural state of semi-paralysis that some animals enter when presented with a threat, which is probably a defensive mechanism intended to feign death, albeit rather poorly.
An early reference of this phenomenon was described in 1646 in Ars Magna Lucis et Umbrae by Athanasius Kircher.