Why You Can’t Tickle Yourself…

It’s pretty much impossible to tickle yourself and get the reaction one my get from being tickled by someone else and the reason why tells us a lot about how the brain works and about consciousness.

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The question of why we cannot tickle ourselves is intriguing and exciting neuroscientists. It in fact leads to bigger questions about consciousness and self awareness. Every time your body moves it can create confusing sensations that could lead one astray in all types of ways. Imagine the chaos if you assumed that someone was attacking you, each time one of your hands went up against your leg, for example. Being able to tell the difference between your movements and the actions of another person, is therefore a centred part of of our sense of self. In examining these types of traits, you want to be able to find an example that is easily duplicated in a lab. Tickling is an easy example because the contrast between ticklish sensations produced by others and the inability to tickle yourself is very clear.

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Sarah Jayne Blakemore from the University College London was one of the first to investigate how the brain makes these lightening speed decisions and the self and others. Experiments showed, from the resulting brain activity, the conclusion was that whenever we move our limbs, the brain’s cerebellum produces precise predictions of the body’s movements and then sends a second signal that damps down the activity in the somatosensory cortex (where the tactile feelings are processed). This concludes that when we tickle ourselves, we do not get the same sensations with the same intensity as if they had come from another person, and so we remain calm rather than wriggling about in a mixture of pleasure and discomfort.

This perhaps being true, it’s suspected that there could be ways to trick the process and therefore allow people to tickle themselves. An experiment conducted, designed a machine that allowed the subjects to move a stick that gently stroked a piece of foam over their palm, sometimes instantaneously, at others with a delay of up to 200 milliseconds. It showed that the greater the delay, the more ticklish the foam felt, maybe because the cerebellum’s predictions did not match what the person was actually feeling.

Since Sarah Jayne Blakemore’s study, many others have tried to understand ways to trick the brain into ‘tickling itself’. Controlling someone’s foot movements with magnetic brain stimulation so that their hand tickled their foot against their will- seems to do the trick! But is is however one of the few experiments to succeed, other experiments have produced confused and puzzling results.

Other experiments included simulating a type of outer body experience and whilst dreaming and neither of those experiments were very successful in achieving the goal. That all might sound a bit esoteric but there could be practical reasons for picking apart the neural processes behind self tickling. ¬†It’s very interesting that people with schizophrenia can tickle themselves, it is though that this is associated with things like delusion and alien control of the limbs. Attempting to break down that process in a mentally well person could eventually shed some light on the way it malfunctions during periods of mental illness.

Another question lurks- could robots one day be sentient enough to be ticklish?

Robert Provine said: ‘Your inability to tickle yourself suggests neurological based definitions of self and other. Developing a similar machine algorithm may lead to ‘ticklish’ robots whose performance is enhanced by their capacity to distinguish touching from being touched and provocatively may provide a computationally based construct of machine personhood.”

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