Hypnotism is a pretty neat party trick—but is it a peculiarly human vulnerability? This video claims to show people hypnotizing a chicken:
This trick often is often called “animal hypnosis,” but, according to Dimitrios Beredimas, an agronomist and blogger at Strange Animals, it’s actually called “tonic immobility" and is quite different from the kind of hypnosis that most of us think of. (No one has yet been able to make the chickens do embarrassing things once they wake up.)
All you have to do is hold the chicken's head down against the ground, and draw a straight line using a stick, a finger, chalk or whatever.
The line should start at the beak and extend straight outward in front of the chicken. If done properly, the chicken -or rooster- will be put into a state of trance and lie still for anywhere between 30 seconds to 30 minutes! To de-hypnotize the chicken just clap your hands or give it a gentle push. It may take a few tries to awaken the bird.
Tonic immobility is what researchers call "a fear-potentiated response” to being restrained. In other words, the chicken (or any other animal that exhibits this response) is convinced that it is going to die and goes into a kind of cationic state. According to Beredimas, farmers have known about this trick at least since 1646, when Athanasius Kircher published "Mirabile Experimentum de Imaginatione Gallinae.” The reaction seems to be most commonly reported in domesticated birds like chickens and quail, but other species seem to demonstrate tonic immobility as well. One study from 1928 looked at the response in lizards. Another watched the brains of rabbits during movement, rest, sleep and tonic immobility.
It's possible that we're susceptible to this reaction, too. Some researchers have suggested that tonic immobility responses might happen during traumatic events like rape. One study looked at whether PTSD patients experience tonic immobility, by asking two groups of patients, one with PTSD and one without, to listen to a script in which they experienced a traumatic event. The researchers watched the patients' posture and brain during the whole thing. It was a small study, but the researchers found that the script did cause the participants some immobility, often at the same time their heart rates sped up, "implying that tonic immobility is preserved in humans as an involuntary defensive strategy."
So, it's not quite right to call this hypnosis—it's not about getting sleeeeepy but about feeling scared.