Neuroscientists Suggest Why We Can’t Tickle Ourselves

Tickles are the only kind of touch that can make you laugh. Despite this, the mechanisms involved in this behavior are not well known – why we can’t tickle ourselves was an example. A study published last month, however, tried to unravel this mystery.

The authors suggest that when the individual tries to tickle himself, the body decreases sensory perception, that is, it becomes less sensitive to touch. Which explains why we don’t feel ticklish while showering or changing clothes.

“Not being able to tickle yourself is a phenomenon linked to something called sensory expectation” says Altay Lino de Souza, researcher at the psychobiology department at Unifesp (Federal University of São Paulo) and creator of the Naruhodo science podcast.

When the tickle is provoked by the other, the body does not know exactly where and how this touch will be and this generates an apprehension, which causes an inspiration and is relieved with a laugh (exhalation). When the individual tries to tickle himself, this apprehension does not exist.

It is not news that an individual cannot tickle himself. Since 1897, researchers have presented this conclusion. What the new study shows is that tickling provoked by the other is also suppressed if the individual is trying to tickle themselves at the same time.

The work, published by German researchers in the scientific journal Philosophical Transactions of the Royal Society B: Biological Sciences, had six pairs of participants and was divided into two stages.

In the first, an individual was seated in a chair and the other was instructed to tickle the first. The facial and chest movements were analyzed, as well as the sounds emitted. In addition, the individual rated the level of tickling. In the second stage, the tickling was done only in the regions where the individual was more sensitive, but now he also tried to provoke laughter in himself.

In addition to trying to clarify the mechanism of tickle suppression, the article shows that there is a correlation between subjective perception and the intensity of laughter. That is, the more ticklish the individual feels, the faster, louder and sharper the laugh.

For Diego Andrés Laplagne, biologist and researcher at the Instituto do Cérebro at UFRN (Federal University of Rio Grande do Norte), this is the most interesting finding of the article, because it manages to measure something that is subjective – the perception of tickling – reliably and quantitative.

According to the biologist, having a study that shows the relationship between what is measured quantitatively and what the individual is actually feeling is a great advance.

The work also indicates that vocalization takes longer to appear than scientists believed. While the movement of the face and chest occurs about 0.3 seconds after the touch that triggers the tickle, the sound of laughter does not appear until about half a second after the touch.

This response time is longer than for a typical ringtone. When the researchers asked subjects to notify when they felt contact on the shoulder, for example, the average time between touch and voice was 0.3 seconds.

Laplagne claims that this is because these two responses come in different ways. Although laughter is an unconscious response, it is more complex and involves the movement of other parts of the body, while the common touch response, even if conscious, needs fewer neurons to activate.

Due to this unconscious characteristic of laughter, the researchers caution that care must be taken. Even if there is no physical danger for excessive tickling, if not for the momentary shortness of breath, the fact that the other is laughing does not mean that they are necessarily feeling pleasure – especially in the case of children.