There are those who do not suffer at all and those who can not be touched in sensitive areas without starting to laugh compulsively. A tickle is a very controversial sensation. Very personal, associated with laughter but also an unpleasant feeling, so much so that we say we “suffer”. Medicine and psychological sciences are still far from having definite answers on this phenomenon, described very correctly by the Encyclopedia Treccani as “a skin and tactile sensation of an unknown nature, with special subjective characters more or less unpleasant, accompanied by often intense defensive reflexes”. Some more progress is emerging in recent years thanks to the tool of functional magnetic resonances, ie those that photograph with different colors, the areas of the brain activated in certain situations. What has been discovered in this sense? We talked about it with Dr. Paolo Amami, neuropsychologist at Humanitas.
In fact, there are two types of tickle: a more intended (gargalesis) in which the intense and repeated solicitation of certain areas of the body provides an automatic response to this type of annoyance/laughter; while another type, induced by a milder stimulation (knismesis), tends to be independent of laughter and is more similar to “itching”. As there are two types of tickle there are also differences between the types of laughter they cause. Tickle laughter is different from fun laughter. The first one also stimulates the hypothalamus, which controls body temperature, hunger, fatigue and sexual behavior. Precisely this part of the brain controls instinctive reactions such as fighting and escaping. The second, on the other hand, involves different areas of the brain.
“According to some evolutionary interpretations – explains Dr. Amami – the duplicity of sensation, that is, associated with both laughter and discomfort, would serve to learn a way of protecting and defending oneself through social play, since childhood teaching the child to protect areas of the body that are particularly vital and ‘defenseless’. It is not by chance that only some parts of the body are sensitive to tickle: armpits, hips at the sides of the ribcage, belly, neck and for some subjects even ears, feet and knee recess.
A primordial defense mechanism
According to the researchers of the University of Tuebingen, the tickle, by activating the part of our brain that anticipates pain, would be the part of a defense mechanism that signals submission as a function of escape. The laughter generated by the tickle would therefore be part of a mechanism of attack or flight. According to this theory, parents tickle their offspring to teach them how to react to danger: a kind of educational game which teaches how to simulate a surrender when our opponent is physically superior to us but actually anticipates a possible and desired escape.
The results of the brain scan
To confirm their thesis, the German researchers have monitored 30 volunteers by connecting them to a special scanner and have submitted them to some questions to understand why the tickle aroused laughter. The participants were first subjected to the vision of some funny scenes that aroused laughter and then exposed to tickle in the most sensitive areas. The laughter in both cases activated the part of the brain called the rolandic region, a region that controls facial movements as well as vocal and emotional reactions. According to another theory, the tickle should be considered in interactive terms, as one of the first means and contexts through which the child learns to consolidate relationships, primarily with the parent. In this sense, the tickle seems to be the evolutionary basis of the following adult humour. In fact, it seems that whoever is more predisposed to tickle is also someone more inclined to humour and smile at daily life.