In the first test, they placed subjects in an MRI and found that fewer areas of the brain were activated, and at a lower intensity, during self touch than when experimenters touched the subjects. In the second test, they asked subjects to touch their own arms and simultaneously poked them with a plastic filament. Then, researchers asked the subjects whether they perceived the filament and where they felt their own touch most—in the hand doing the touching or the arm receiving the touching. In the third test, experimenters placed an electrode on subjects’ thumbs and used it to track how quickly the brain processes information from self touch and touch by others.

They found that the perception of self touch was lower priority for the brains of their test subjects than the perception of touch by other people. That wasn’t too surprising. What did come as a surprise was the level of difference between the touch signal from others and from self touch. “This extreme difference was not something I expected,” Böhme says.

This study demonstrated that test subjects’ brains clearly understood the difference between self-touch and touch by others, and weighted those two experiences differently. “Me” versus “not me” is defined by touch.