Scientists trick the brain into Barbie-doll size

May 25, 2011, Public Library of Science
Henrik Ehrsson and Björn van der Hoort conducting an experiment. Photo: Staffan Larsson

(Medical Xpress) -- Imagine shrinking to the size of a doll in your sleep. When you wake up, will you perceive yourself as tiny or the world as being populated by giants? Researchers at Karolinska Institutet in Sweden may have found the answer.

According to the textbooks, our of size and distance is a product of how the brain interprets different visual cues, such as the size of an object on the and its movement across the visual field. Some researchers have claimed that our bodies also influence our perception of the world, so that the taller you are, the shorter distances appear to be. However, there has been no way of testing this experimentally – until now.

Henrik Ehrsson and his colleagues at Karolinska Institutet have already managed to create the of body-swapping with other people or mannequins(Now they have used the same techniques to create the illusion of having a very small doll-sized body or a very large, 13-foot tall body. Their results, published in the online open access journal PLoS ONE, show for the first time that the size of our bodies has a profound effect on how we perceive the space around us.

"Tiny bodies perceive the world as huge, and vice versa," says study leader Henrik Ehrsson.

The altered perception of space was assessed by having subjects estimate the size of different blocks and then walk over to the blocks with their eyes shut. The illusion of having a small body caused an overestimation of size and distance, an effect that was reversed for large bodies.

One strategy that the uses to judge size is through comparison – if a person stands beside a tree it computes the of both. However, the sensed own body seems to serve as a fundamental reference that affects this and other visual mechanisms.

"Even though we know just how large people are, the illusion makes us perceive other people as giants; it's a very weird experience," says Dr Ehrsson, who also tried the experiment on himself.

The study also shows that it is perfectly possible to create an illusion of body-swapping with extremely small or large artificial bodies; an effect that Dr Ehrsson believes has considerable potential practical applications.

"It's possible, in theory, to produce an illusion of being a microscopic robot that can carry out operations in the human body, or a giant robot repairing a nuclear power plant after an accident," he says.

More information: van der Hoort B, Guterstam A, Ehrsson HH (2011) Being Barbie: The Size of One's Own Body Determines the Perceived Size of the World. PLoS ONE 6(5): e20195. doi:10.1371/journal.pone.0020195

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2 / 5 (3) May 25, 2011
This can be used for good or for evil.

Good - giving people the illusion that they are the size and shape of a robot cleaning up nuclear waste, or some other relevant task. They could work more efficiently and safely.

Evil - This could be the next e-doser, and you could have a wave of perception junkies walking down the street, freaking out over every crack and pebble in the sidewalk, afraid that they can't climb over it.

Ok, maybe the second part is ridiculous, but that's just how the news works (see e-doser news articles/news reports)

That said, I really want to try this. The article needs more info, and instructions.
5 / 5 (3) May 25, 2011
That said, I really want to try this. The article needs more info, and instructions.

The linked paper ( has the entire experiment described in detail with figures and images of the setup. You don't even have to pay to access this one.
2.8 / 5 (4) May 25, 2011
I know people who don't have to be tricked into having Barbie sized brains.
not rated yet May 25, 2011
Folklore Adages:
When on edge, everything looks further away. (Both meanings)
Little things for little minds (Dispelled by particle physics)
Unit of measure determines length (Mandelbrot)
Prospective is everything (Unknown)
No brainer (Unknown)
1 / 5 (1) May 25, 2011
Scientists trick the brain into Barbie-doll size
Can they trick people into believing they have Barbie's body and cool wardrobe as well?
not rated yet May 25, 2011
Only your hairdresser knows for sure.

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