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 perception of size and distance is a product of how the brain interprets different visual cues, such as the size of an object on the retina 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 hypothesis experimentally - until now.
Henrik Ehrsson and his colleagues at Karolinska Institutet have already managed to create the illusion 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 brain uses to judge size is through comparison - if a person stands beside a tree it computes the size 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.
Citation: 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
Funding: This work was supported financially by the European Research Council, the Swedish Foundation for Strategic Research, the Human Frontier Science Programme, the James S. McDonnell Foundation, and the So¨ derbergska Stiftelsen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Disclaimer: This press release refers to upcoming articles in PLoS ONE. The releases have been provided by the article authors and/or journal staff. Any opinions expressed in these are the personal views of the contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the release and article and your use of such information.
About PLoS ONE
PLoS ONE is the first journal of primary research from all areas of science to employ a combination of peer review and post-publication rating and commenting, to maximize the impact of every report it publishes. PLoS ONE is published by the Public Library of Science (PLoS), the open-access publisher whose goal is to make the world's scientific and medical literature a public resource.