Conference report

For the next trick we will need a beautiful assistant wearing a sequined body-suit [curtsey, radiant smile from Vulnavia]; a table with a kind of drawer or visual shield; and a rubber hand.

Slip your hand into the drawer on the table-top so it is concealed from your view, while I place the rubber hand beside it. From her side of the table, Vulnavia starts tapping or stroking the back of the two hands, slow regular taps, in synchrony.

The neat part is that your mind soon comes to the reasonable conclusion that the in-full-view tapping of the rubber hand must be the same as the sensation of being tapped, and your body image shifts to occupy the fake -- that is, you feel the sensation coming from what you know perfectly well to be a lump of moulded silicone.

One interpretation is that body image is not fixed. Perhaps it is constantly being constructed afresh, much like Highway 1 leading out of Wellington. The illusion affects proprioception (your keeping-track of where each body appendage is currently located) so if you're asked to move your hand behind the visual screen to grasp some object -- STOP THAT VULNAVIA -- you make errors.

While this is happening, the skin temperature of your real hand drops; some researchers use this temperature change as a sign that the illusion has taken hold. In a variant experiment, Vulnavia interrupts the visible stimulation by holding her own hand a few inches away from the rubber dummy, while continuing the hidden taps behind the screen; people report all sorts of "invisible finger" sensations as their mind struggles to accommodate the dissonance.

The hand does not have to be realistic! Such is the MAGIC OF THE MOVIES that people will accept a white cardboard box as a substitute for their hand as long as Vulnavia keeps up tapping it in synchrony with the unseen stimulation to the back of the box real hand; or even the table-top itself according to Armel & Ramachandran (though Tsakiris & Haggard couldn't replicate this).*

Is it working yet?

Very good. Vulnavia, the hammer please. Give us all your money or THE FURNITURE GETS IT!!

* In theory, with the right stimulation, I suppose a guy could be persuaded to accept a sportscar (say) as a proxy or extension of his penis, but LET'S NOT GET RIDICULOUS.