Real or fake? Hard to tail Ingo Arndt/Naturepl.com/Getty

It’s a tale of two tails. Mice can be tricked into thinking fake tails are their own, using the same “rubber hand illusion” that works in people. The illusion helps us understand how our brains create a sense of body ownership and awareness. The discovery that mice fall for the same trick could aid the development of prosthetic limbs and treatments for psychiatric disorders.

In the human version of the trick, a person sits next to a rubber hand and their own hand is hidden. Stroking both hands at the same time tricks the person into feeling that the rubber limb is their own. When the fake hand is attacked, people yell out in fear – as if their own limb were under threat.

Kenji Kansaku at the National Rehabilitation Center for Persons with Disabilities in Tokorozawa, Japan, and his colleagues performed the same trick on mice, hiding their tails and using a fake one.


When the fake and real tails were stroked out of sync, the mice didn’t react to the fake tails being approached. But when their own tail was stroked simultaneously with the fake one, they reacted strongly, twisting as if to pull the fake tail away.

Henrik Ehrsson at the Karolinska Institute in Stockholm, Sweden, was surprised by the result. In people, a brain region called the parietal association cortex is important for body ownership. This region is tiny in mouse brains, he says.

Studying the activity of various brain cells in mice during the illusion – something you can’t do in humans – could offer plenty of insights, says Ehrsson. For example, knowing the precise brain activity involved could shed light on disorders in which body awareness is disrupted, such as schizophrenia, and help with the development of prosthetic limbs that are more easily incorporated into body image.

Journal reference: Journal of Neuroscience, DOI: 10.1523/jneurosci.3006-15.2016