BRAIN'S IDEA

Ideas for brainy people by someone who minds.

Three fun ways to have three hands – for you at home July 31, 2012

Tired of having been born with only two hands?

Jealous of Indian goddesses?

Doubtful about Psychology and Neuroscience’s ability to replicate findings?

Then this set of exercises is for you. No need for any technical equipment. If all goes well you will grow* a hand as part of all this. You will have the strong feeling that you have three hands. You will feel and/or care about the illusory third limb. Let’s get started.
.
1) An additional cheeky hand
Equipment: none
Partners needed: 1
Time: 3 minutes
Success rate: 43% (70% report some sort of self-touch illusion)
Publication: Davies & White (2011)
a) Your partner and you place your hands on the same warm water bottle in order to have equally warm hands.
b) Sit down and close your eyes. Your partner sits opposite you. Her eyes are open.
c) Your partner takes your right hand and makes you stroke and tap yourself lightly on your right cheek. At the same time she herself administers synchronous, identical strokes and taps with her hand to the corresponding location on your face’s left side. Your own left hand simply rests.
d) Vary pressure and frequency of strokes and taps. Mind that on each side of the face timing and pressure have to match. Do so for three minutes.
Davies and White, 2011_cheeky hand illusion

Set-up to add a cheeky hand.

Outcome: The feeling that some sort of third hand, a disconnected one for example, strokes your left cheek.
.
2) Two rubber hands
Equipment: two rubber/plastic/wooden or otherwise somewhat realistic feeling right hands, a table, one double paint brush (see picture), one normal paint brush
Partners needed: 1
Time: 2 minutes
Success rate: not reported
Ehrsson, 2009_two rubber hands

Set-up to induce two rubber hand illusions simultaneously.

Publication: Ehrsson (2009)
a) Sit at a table. Place your right hand underneath the table, e.g., on your leg.
b) Place the rubber hand models of right hands in front of you over the area where your real right hand is. The models should be 10cm apart.
c) Look at the rubber hands. At the same time you partner uses the double paint brush to stroke the rubber hands and the single paint brush to stroke your real hand. These strokes need to be absolutely in synchrony.
Outcome: The feeling that both rubber hands are your right hands.
.
3) An additional rubber hand
Equipment: a rubber/plastic/wooden or otherwise somewhat realistic feeling right hand, a table, two paint brushes, a piece of cloth
Partners needed: 1
Time: unknown
Success rate: unknown
Publication: Guterstam, Petkova, & Ehrsson (2011)

Left: Set-up to add rubber hand to one’s own body. Right: Testing how real the ownership of the rubber hand really is (don’t do this test at home).

a) Sit at a table. Put your real right hand on the table in front of you.
b) Place the rubber hand in a similar position slightly to the left of your real hand, about 12cm apart. Cover the space from your real shoulder to the arm-bit of the rubber hand with the cloth.
c) Look at the rubber hand. At the same time your partner uses the two paint brushes to stroke both your real right hand and the rubber hand simultaneously on the index and middle fingers. She needs to do so absolutely synchronously, matching the strokes in time and speed. It is best to stroke irregularly but still synchronously.
Outcome: The feeling that both the real hand and the rubber hand are your right hands.
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Did these illusions work for you? Let me know!
As a bonus for all those still in for some more, the following two techniques substitute your real hand for a fake one.
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Bonus 1) A rubber hand (with vision)
Equipment: a rubber/plastic/wooden or otherwise somewhat realistic looking hand (it can be a bit bigger – but not smaller – than your real hand and it can also have a different ‘skin’ colour), two identical paint brushes, one standing screen (a big book would do as well), one table
Partners needed: 1
Time: 10 minutes
Success rate: 42%
Publication: Botvinick & Cohen (1998)
a) Sit at a table. Place the screen in front of you and hide your left hand behind it. Be sure you cannot see your left hand.
b) Place the rubber hand model of a left hand in front of you on the table.
c) Look at the rubber hand. At the same time your partner uses the two paint brushes to stroke both your hidden hand and the rubber hand simultaneously. She needs to do so absolutely synchronously, matching the strokes in time.
Outcome: The feeling that the rubber hand is your own hand.
.
Bonus 2) A rubber hand (without vision)
Equipment: a rubber/plastic/wooden or otherwise somewhat realistic feeling hand, three pairs of rubber gloves, a table
Partners needed: 1
Ehrsson et al., 2005: rubber hand illusion without vision

Top: Set-up for inducing rubber hand illusion without vision. Bottom: same in a MRI scanner.

Time:  60 seconds
Success rate: 78%
Publication: Ehrsson, Holmes, & Passingham (2005)
 a) Both you, your partner and the rubber hand need to wear rubber gloves.
b) Sit at a table. Place the rubber hand model of a right hand in front of you on the table. Close your eyes.
c) Your partner takes your left hand and makes you touch the rubber hand’s index finger’s knuckle. At the same time she herself administers synchronous, identical touches with her hand to the corresponding location on your own right index finger’s knuckle.
Outcome: The feeling that you are touching your own hand even though you are touching the rubber hand.
.
Finally, if you now wonder whether scientists have also found a way to make you lose a hand, just watch this video. Unfortunately, the techniqual requirements go beyond what is available in most homes and so your own private replication of this illusion will be rather difficult to implement.
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Aimola Davies, A.M., & White, R.C. (2011). Touching my face with my supernumerary hand: A cheeky illusion Perception, 40, 1245-1247 DOI: 10.1068/p6956

Botvinick, M., & Cohen, J. (1998). Rubber hands ‘feel’ touch that eyes see. Nature, 391 (6669) PMID: 9486643

Ehrsson, H.H. (2009). How many arms make a pair? Perceptual illusion of having an additional limb. Perception, 38 (2), 310-312 PMID: 19400438

Ehrsson, H.H., Holmes, N.P., & Passingham, R.E. (2005). Touching a rubber hand: feeling of body ownership is associated with activity in multisensory brain areas. The Journal of neuroscience : the official journal of the Society for Neuroscience, 25 (45), 10564-10573 PMID: 16280594

Guterstam, A., Petkova, V.I., & Ehrsson, H.H. (2011). The illusion of owning a third arm. PloS one, 6 (2) PMID: 21383847

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images: from respective journal publications

*in a psychological sense

ResearchBlogging.org

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5 Responses to “Three fun ways to have three hands – for you at home”

  1. [...] "CRITEO-300×250", 300, 250); 1 meneos Tres formas caseras para tener tres manos brainsidea.wordpress.com/2012/07/31/three-fun-ways-to-hav…  por SraEspiroqueta hace [...]

  2. Wanted to do a ‘rubber hand’ experiment… but can’t find a suitable rubber hand anywhere! Any suggestions?

    • Ehrsson et al., 2005 simply refer to ‘A rubber, life-size prosthesis of a male or female right hand (gender matched) was placed on the table between the participant’s hands (15 cm to the left of the participant’s right hand).’

      I guess if I were you I’d go for a mannequin hand as used in shop windows.

  3. [...] Three fun ways to have three hands – for you at home [...]


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