It is well known that we can't tickle ourselves. But can you tickle yourself if you are fooled into thinking that someone else is tickling you? George Van Doorn, Jakob Hohwy and Mark Symmons decided to test this idea by having people either tickle themselves or having someone else tickle them while simultaneously subjecting people to a body swap illusion. They found that people couldn't tickle themselves even under the influence of the illusion, challenging a widely accepted theory about how our brains work.
Specifically, their findings fail to support those of Blakemore and colleagues. If the brain makes fine-grained predictions based on actual motor commands to figure out when to dampen the tickle response, then those predictions should fail during the illusion, since the command to move doesn't result in the sight of your own hand moving – enabling one to tickle oneself. Van Doorn, Hohwy and Symmons believe that the work lends support to an idea called “active inference”, developed by Karl Friston, which argues that the brain attenuates incoming sensations anytime we make a movement. “[So] you should not be able to tickle yourself, no matter what the context,” says Hohwy.
Read more in New Scientist current edition.