Why can’t you tickle yourself?

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Text: Ola Danielsson for Medical Science no.4, 2022

Welcome Constantina KeltiniCan you explain why it’s so hard to tickle yourself?

This is because the brain can anticipate and suppress the sensory effects of body movements. For example, when we reach for something, the brain anticipates how the touch will feel. But if someone else touches us, or if a spider crawls onto our arm, the brain can’t predict what will happen based on its own movements, and so we feel more ticklish.

Why is this phenomenon important to study?

– It gives us access to the mechanism that the brain uses to distinguish between signals from the body and signals that come from outside. It may be clinically interesting, as we know, for example, that people with schizophrenia have difficulty distinguishing between sensations generated by their own body and sensations generated by other people. A possible explanation for the voices some people with schizophrenia hear is that the brain interprets its thoughts as if they were someone else’s. In fact they also find it easier to tickle themselves compared to healthy controls.

you work onTouch and tickleLab. What are you doing there?

– We do experiments with healthy people where they can indicate how intense or sensitive a touch feels depending on whether it comes from the person themselves, a device or another person. For example, we use robots that can generate touch on different parts of the body, and let people describe how they feel compared to if the person was controlling the robot itself. We also do brain imaging studies to find out which parts of the brain differentiate between touch from one’s own body and external touch.

What did you come up with?

We recently discovered that even healthy people with certain personality traits that resemble clinical symptoms of schizophrenia had a reduced ability in our tests to predict what subjective movements would feel like. This could mean an increased risk of schizophrenia, but more research is needed to confirm this.

Why do you laugh when you are tickled? He actually feels completely uncomfortable.

It’s an interesting question that we don’t know the answer to. Usually, the person being tickled tries to move away from the object that is being tickled, while laughing as if in fun. But many people actually find it uncomfortable. It has been said that laughing when tickled is a neurological reaction that differs from laughing when we hear a joke, for example. It’s not entirely clear, but it’s most likely two different reactions.