Illusions of Invisible, alien hands, 3 arms, and shrinking bodies…

I have previously posted about the original ‘rubber hand illusion‘ in which participants are convinced a fake rubber hand is their own. A classic low tech experiment that can help us “understand how sight, touch and “proprioception” the sense of body position, combine to create a convincing feeling of body ownership, one of the foundations of self-consciousness  (Nature 1998, vol 391, p 756 )” Further to this research recent studies have gone on to experimentally induct of out of body experiences or create body swap illusions. [ Henrik Ehrsson and Olaf Blanke http://www.eurekalert.org/pub_releases/2007-08/ucl-foe081407.php ] Between these two experiments, several interesting versions of hand-related experiments also exist which demonstrate the plasticity of our body perception…

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The Alien-Hand Experiment (Nielsen 1963;1978 https://link.springer.com/article/10.1007/s11097-005-5854-4]  

The Alien Hand Experiment first created in the 1960s predates the Rubber hand experiment, seems more ‘trick’ than an experiment, but the element of deception is necessary, participants are asked to draw a straight line while viewing their gloved hand in a mirror. Unbeknown to them, they are viewing the experimenter’s hand mimicking their own actions. This could also relate to the Alien hand syndrome [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4059570/ ] a rare condition in which a person believes their hand is controlled by someone else.

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[Guterstam, Gentile & Ehrsson. 2013. The Invisible Hand Illusion: Multisensory Integration Leads to the Embodiment of a Discrete Volume of Empty Space. J Cogn Neurosci http://dx.doi.org/10.1162/jocn_a_00393 ]
The Invisible Hand Illusion is a version of the Rubber hand illusion which uses no hand at all as the fake hand, sometimes a handless stump, and as a control, a wooden plank. they found that participants could embody a ‘Discrete Volume of Empty Space’ a concept which personally I find too exciting not to try at the next available opportunity.

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[Guterstam, Petkova & Ehrsson. 2011. The Illusion of Owning a Third Arm. PLoS ONE http://dx.doi.org/10.1371/journal.pone.0017208]
This experiment uses a rubber hand placed next to the real hand of the participant. They found participants were able to feel as if they had two hands, as long as they were both the same hand [left or right]

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Stelarc ‘Third Hand’

There is obvious resonance here with the work of Stelarc http://stelarc.org/?catID=20265  whos project ‘Third Hand’ as he explains “A mechanical human-like hand that is attached to my right arm as an additional hand. It is made to the dimensions of my real right hand.”

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[van der Hoort, B., Guterstam, A., & Ehrsson, H. (2011). Being Barbie: The Size of One’s Own Body Determines the Perceived Size of the World 10.1371/journal.pone.0020195 ]
The project “Being Barbie: The Size of One’s Own Body Determines the Perceived Size of the World” Builds on the set up created for the body swap illusion and plays with body scale with fascinating results.

There are more but will have to wait for another post.

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