Tickling, because you can’t do it yourself

In the next phase of the experiment, the “ticklers” repeated the action of the previous stage, while their partners did they tried to tickle themselves (in the same point but on the opposite side of the body, just next to it or simulating the act without touching the skin).

As expected, attempts to self-tickling had no effect. However, the team noticed something strange: the act it made the other person’s tickle less intense. On average, laughter decreased by 25 percent and was delayed by nearly 700 milliseconds when the same areas were affected. “It was a surprise – explains Brecht -. But it came out very clearly in the data “.

Predictability and inhibition

How can this phenomenon be explained? To answer, we need to go back to the question of why we can’t tickle ourselves. The main theory holds that the tickle causes laughter thanks to a prediction error of the brain, which is confused by an unexpected touch and goes into fibrillation. Attempts to tickle yourself, however, are always predictable.

But Brecht thinks the point is not the ability to predict. The researcher suggests instead that when a person touches their body, the brain sends a message to the whole body by inhibiting the sensitivity to touch. If this were not the case, Brecht argues, we would continually tickle ourselves every time we scratch an armpit or touch our toes.

The theory makes sense, says Sophie Scott – a cognitive neuroscientist at University College London not involved in the research – because the our brain learns to attenuate sensory perceptions when our actions contribute to causing them. The same darkening effect, he continues, occurs with hearing. As we speak, the parts of the brain that other people listen to are suppressed. (That’s why, Scotto continues, “people are unable to judge the volume of their voice”). Kilteni notes that it is not yet clear what exactly happens in the nervous system when a person is tickled, even self-inflicted. However, the neuroscientist is impressed by the data that Brecht’s team was able to collect.

The face does not say everything

The contribution of lab tickling sessions to science goes beyond the fun side. They also clarify little-studied aspects of emotional processing. “People say that we don’t express emotions very intensely with our voice, which is the job of the face Says Scott, who couldn’t disagree more. The voice expresses words, moods, identity, health, age, sex, gender, geographical origins and socioeconomic status: they’re just harder to study than faces“. Scott adds that even the touch is much underestimated. Compassion and affection are expressed much more clearly with touch than with faces or words.

Brecht’s team intends continue studying the game through neuroscience in future studies. Experts have speculated that the level of susceptibility to tickling reflects the perception we have of ourselves regarding our playfulness. While this aspect seems true for other animals – a rat that is in great pain tickle it’s also more playful – it’s more questionable for humans. “My wife is ticklish more – says Brecht -. But I’m very playful! “.

This article originally appeared on Wired US.