In science fiction and fantasy tales, there is a long running fascination with the idea of dramatically diminishing or growing in stature. In the 1989 classic, Honey, I Shrunk the Kids, Rick Moranis invents a device which accidentally shrinks both his own and the neighbor’s children down to a quarter-of-an-inch tall. Preceding this by more than 100 years, Lewis Carroll wrote about a little girl who, after tumbling down a rabbit hole, nibbles on some cake and then grows to massive proportions. Nearly 300 years ago, Jonathan Swift described the adventures of Gulliver while on the island of Lilliputan, on which he is a giant, and then on the island of Brobdingnag, where everyone else is a giant.
These kinds of experiences, however, have been limited to the world of fictional stories. The world around us does not actually change in size. Nor, with the exception of too many late-night Chinese deliveries, do our bodies become appreciably larger or smaller.
Or at least, they were mythical until recently. A research group at the Karolinska Institute in Sweden has managed to make people feel as though they actually inhabited bodies of vastly different size – either that of dolls or of giants. The researchers showed that this fundamentally changed the way people perceived the physical world. Those in smaller bodies felt as though they were in a world populated by giant hands and pencils the size of trees, while those in giant bodies felt the same objects to be tiny, toy-sized versions of the real thing.
In order to accomplish this trick of self-displacement, participants in the experiments lay on a bed and wore a head-mounted display connected to two video cameras. These cameras faced a fake body lying on a bed next to the participant; thus, when participants looked down toward their own bodies, they instead saw artificial bodies where their own should have been. These artificial bodies were either huge (a 13-foot form made of chicken wire) or very small (a Barbie Doll).
In order to make participants feel ownership over these false bodies, researchers employed a technique well known to those interested in body perception. Participants would place their hands out of view, perhaps under a table, while an artificial hand sat atop of the table. The experimenter then stroked both the obscured real hand and the visible fake hand synchronously. As a result, participants would witness a hand in roughly the same position as their own being touched in precisely the manner that they felt themselves to be touched. This had the effect of making the majority of participants feel the false hand to be their own. This method has been shown to work with whole bodies – it even allows a participant to feel as though he or she is sitting in another person’s body, shaking hands with their self!
For this set of experiments, after demonstrating that people could experience an extremely large or small body as their own, the researchers then investigated the consequences. Specifically, do participants feel as though they are actually living at a different size? Or do they feel body size to remain constant, while the size of the world around them changes?
The researchers used a number of measures to answer this question. They had participants estimate their distance from a box on the ground, and had them open their hand to the width of the box as if they were going to grasp it. Participants in small bodies consistently estimated the box to be farther away, and tended to use a wider grip, as if preparing to pick up a box much larger in size. Conversely, participants in large bodies estimated the box to be much closer, and used a much smaller grip, as if the box had actually shrunk. Thus, in addition to showing that people can feel ownership over differently sized bodies, this research is also another empirical example that our perceptions of the world and our perceptions of our bodies are closely linked.
Though to some, these experiments may seem to be no more than glorified parlor tricks, findings from this line of research have a very useful application. The same principles behind this body-swapping illusion were recently established to be an effective treatment for arthritis pain, since they allow sufferers to feel as though their cramped fingers are being stretched to impossible lengths, thus providing relief from their pain.
This research also adds to a growing body of literature that demonstrates that the world we perceive is not an identical copy of the physical world. Hills appear steeper when we are wearing heavy backpacks, objects appear closer when we desire them, and, as shown here, the world appears larger when we are in a smaller body. Although the world does not actually physically change in these ways, our mind seems to be constructed in such a way that allows a surprising degree of flexibility in perceiving the physical nature of the world. As scientists work to determining the limits and uses of this flexibility, we will likely be treated to an assortment of findings which may seem to come straight out of fiction.
Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook, a Pulitzer prize-winning journalist at the Boston Globe. He can be reached at garethideas AT gmail.com or Twitter @garethideas.