Why can’t you tickle yourself?

Stop what you’re doing and try and tickle yourself - it’s impossible, right? This might seem strange considering the lightest touch from someone else, for example on the back of the arm, can have you in fits of laughter, but scientists have proven that the brain simply will not allow for ‘self-tickling’.

Scientists say it is the cerebellum that prevents humans from having the ability to tickle themselves. The cerebellum is the part of the brain that’s located at the back of the skull, which coordinates and regulates muscular activity and monitors our movements. It can distinguish expected sensations from unexpected sensations

Sarah-Jayne Blakemore, a neuroscientist from University College London, was one of the first to investigate the way the brain makes decisions regarding tickling. 

In a study led by Blakemore, 16 participants had their brains scanned to record cerebral reactions when they were tickled by someone else and when they attempted to tickle themselves. 

Blakemore explains that there are two parts of the brain that are responsible for how we process the action of being tickled. These are: the somatosensory cortex, which is responsible for perceiving touch, and the anterior cingulate cortex, which processes pleasure. These two brain regions work together to trigger the nervous system when someone or something is tickling you. 

There are actually two types of tickles - gargalesis and knismesis. Gargalesis is the type of tickling that causes laughter and uncontrollable body movement, while knismesis is when something tickles you slightly, causing you to flinch.

Participants involved in the study had the palms of their hands tickled and then were asked to  attempt to tickle their own hand. The study found that when someone attempts to tickle themselves, the cerebellum ‘predicts’ the upcoming action, which cancels out the tickle before the sensation can take over. The results also showed that the the somatosensory cortex and anterior cingulate cortex are much less active when someone is trying to tickle themselves. 

Blakemore explained: “Our studies at University College London have shown that the cerebellum can predict sensations when your own movement causes them but not when someone else does, this is why it is not possible to tickle yourself.”

The researchers have found  a way to ‘trick’ the brain, with the assistance of the robot tickler. The team of scientists came up with the idea of designing and building a robot to allow people to, in a way, tickle themselves. 

"Further studies using robots showed that the presence of a small delay between your own movement and the resulting tickle can make the sensation feel tickly. The longer the delay, the more ticklish it feels. So it might be possible to tickle yourself if you are willing to invest in a couple of robots!, Blakemore added.

Tickling is essentially an alert telling you that something is touching sensitive areas of your body - for example, your back, feet, or armpits - this means your brain doesn’t bother to signal when it knows where the source is coming from, which is why it’s not possible to tickle yourself. 

Continue reading