Tuesday, October 29, 2013

Transcendence and Body Maps

The next part of our puzzle concerns the way the mind keeps track of the body and its location with respect to its environment. Here’s how Sandra and Matthew Blakeslee describe it in their book, The Body Has a Mind of Its Own:
Stand up and reach out your arms, fingers extended. Wave them up, down, and sideways. Make big circles from over your head down past your thighs. Swing each leg out as far as you can, and with the tips of your toes trace arcs on the ground around you. Swivel and tilt your head as if you were craning to butt something with your forehead or touch it with your lips and tongue. This invisible volume of space around your body out to arm’s length—what neuroscientists call peripersonal space—is part of you.
This is not a metaphor, but a recently discovered physiological fact. Through a special mapping procedure, your brain annexes this space to your limbs and body, clothing you in it like an extended, ghostly skin. The maps that encode your physical body are connected directly, immediately, personally to a map of every point in that space and also map out your potential to perform actions in that space. Your self does not end where your flesh ends, but suffuses and blends with the world, including other beings. Thus when you ride a horse with confidence and skill, your body maps and the horse’s body maps are blended in a shared space. When you make love, your body maps and your lover’s body maps commingle in mutual passion. [p.4]
A little bit later in the book, they say
Your body schema feels reliable and stable most of the time, so you may be surprised at how mutable it can be under the right circumstances. Using certain tricks you can induce somatic illusions to make parts of your body feel like they are growing, shrinking, bending, embodied in foreign objects, or otherwise displaced in impossible ways. [p.32]
I’ve added emphasis in three spots that are especially relevant. The first two, about blending your self with other beings and mingling body maps with your lover, are obviously relevant, but what about the third point? What do they mean by “embodied in foreign objects”?

Gaining a Hand

The easiest answer is to show you. This is an experiment that you can easily do yourself if you can make or locate the right prop: a life-sized model of a hand. You can buy one at a prop store or mannequin supply store, borrow one from a department store, order one online, or even make one out of plaster or by filling a rubber glove with sand or dirt. Whatever your source, try to get one that is reasonably natural looking, although I have found color and size to be more important than perfect shape.

You will also need:

  • a freestanding divider that is at least a foot tall, such as a cardboard L cut from a box
  • a small table, like a card table or kitchen table
  • two small identical brushes
  • two ice cubes, partly wrapped in paper towels
  • a small towel
  • your partner 

Ideally, the table should be small enough so that you and your partner can sit opposite each other and hold hands across it without stretching.

I’m going to assume that the model hand you have is a left hand. If not, reverse these directions appropriately.

Place your left hand on the table and arrange the divider so you can’t see your left forearm and hand. Place the model hand next to the divider where you can see it. Aside from being offset a bit to the right, the model should be located and oriented just like your real hand. Cover the wrist of the false hand and the place where the forearm would be with the towel.

Now have your partner sit down opposite you and begin stroking both your real left hand and the fake left hand with identical touches, using fingers, the brushes, and the ice cubes in rotation. Your partner needs to try hard to touch exactly the same spots on the two hands in the same way at exactly the same times, so that you see, for example, a brush stroking the fake hand’s ring finger at the same moment that you feel a brush stroking your own ring finger.

After a few minutes, something really strange will start to happen. You will start feeling that the artificial hand is your own hand.

Now close your eyes. After a moment, use your right hand to point to your left hand. Open your eyes and see where you are pointing. Surprised?

(If you can’t do the experiment yourself, or don’t want to take the time, just Google “rubber hand illusion.” You should find several short videos available. Also, for what it’s worth, some people say that you can do this just by tracing your hand on cardboard and cutting out the silhouette. If you do this, omit the ice cube and use glue or double-sided tape to fasten the cardboard hand in place so it doesn’t slide around with every light touch.)

Most people find this really spooky because the hand is so obviously fake, yet it feels so real. To see just how strong the illusion is, the original experimenters wired subjects with sensors before doing the experiment, and at the end of the experiment they suddenly smashed the fake hand with a mallet or stabbed it with a knife! In each case, the subjects gasped and flinched away, and their heart rate and galvanic response changed in exactly the way they would if you threatened their real hand with harm.

Even more weird: your real hand’s temperature falls while you are feeling the fake hand as your own. Apparently your brain “disowns” your real hand and stops regulating its temperature!

By every way that can be measured, this illusion does not fool your conscious mind – you know quite well that the hand is fake – but it does change your brain in such a way that it temporarily incorporates the fake hand into your body image. As the Blakeslees said, “Your body schema feels reliable and stable most of the time, so you may be surprised at how mutable it can be…”

Body Transfers

The creators of the rubber hand illusion, Matthew Botvinick and Jonathan Cohen, have since demonstrated that we can also “adopt” a third arm that is placed in front of us, even when the other two arms are still visible.

Other scientists have been inspired by these results to come up with many more illusions, including an extremely convincing full-body transfer to a life-sized mannequin or another person. In an experiment designed by Henrik Ehrsson and Valeria Petkova, subjects who feel like they are inhabiting another person’s body are asked to shake hands with themselves. When they do this, they report feeling the handshake independently through both arms and both bodies.

Similar results can be achieved with a virtual reality simulation. Note that in the next case, changing gender did not inhibit the body swap in any way:
One of the ways in which body transfer illusion has been studied is through virtual reality simulation where a first person perspective of a life-sized virtual human female body has appeared to substitute the male subjects' own body. This was demonstrated subjectively by questionnaire and physiologically through heart-rate deceleration in response to a threat to the virtual body. The results support the notion that bottom-up perceptual mechanisms, such as those involving the premotor cortex and cerebellum, can temporarily override top down knowledge, therefore resulting in a radical illusion of transfer of body ownership.  [Emphasis added.]
Reviewers who received advance models of the Oculus Rift headset almost immediately used them to create videos of the body swap illusion.  However, as you have probably guessed, I’m going to argue that Tantra does the same thing, more slowly, but better.

Putting the Pieces Together

Let's start with the experiment in which a subject who feels like he is inhabiting the other person’s body shakes hands with his own real body. This provides us with three important clues to what happens in Tantra. First, it demonstrates that these so-called “body swap” illusions do not really “swap” or replace the sense of one body with the other; instead, the subject is “in” both bodies at once. Second, it shows that the gender of the other body is not an issue. Third, it demonstrates conclusively that feeling contact through both bodies at once does not ruin the illusion.

This last point should not be terribly surprising. After all, we are all familiar with what it feels like when we touch one part of our body with another part. When you touch your finger to your nose, you feel both sides of the touch. When you touch the same finger to your genitals, it feels different from both sides, but it isn’t confusing. We are, in fact, quite well prepared to experience touch from both sides simultaneously.

What happens during Tantra, if we know our partners, their bodies, and their responsiveness to our touch extremely well, is that our mirror neurons supply our partner’s side of each touch so convincingly that it can trigger an exceptionally effective body-sharing illusion. Our minds extend our somatic maps and incorporate our partners’ bodies, just as they do during the rubber hand illusion – except that this is a living, breathing, full-sized person, not an inanimate object!

We know that this can happen even in other circumstances, because the phenomenon has also been described by many people who knew nothing about Tantra. Prolonged, intense physical pleasure and sexual euphoria are apparently enough to trigger this state. Most of us take descriptions of union with the beloved as merely a poetic image, but it occurs in too many different cultures and times, from Genesis and Aristotle to ancient Hindu, Persian, and Chinese writings, right up to modern times. Once you have experienced it yourself, it is clear that most of these writers are describing the same subjective reality.

What seems to be special about Tantra is that it stacks the deck so heavily in favor of something that is normally quite rare. Think about it. Almost all of the couples I interviewed undergo a profound body-sharing experience at least occasionally, and more than half experience it routinely. We must be doing something right!

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