When a person is tickled, his nervous system responds to the tickle with body reflexes such as laughter. Scientists today explain this mechanism primarily through what is known as the relief theory. When pathological tickling episodes occur, there is usually a sensitivity disorder.
What is tickling?
When a person is tickled, his or her nervous system responds to the tickle with body reflexes such as laughter. Light touch can trigger a reflex in the form of involuntary laughter or crying. This reflex provocation is also called tickling. Scientists distinguish between knismesis and gargelesis in this context. The former phenomenon involves gentle provocation by light touch. Gargelesis, on the other hand, means the provocation of an almost painful tickle attack. In this case, light to heavy pressure is applied to sensitive areas of the body. Within the human community, tickling is a form of social interaction. In the vast majority of cases, people only respond to tickling when someone else tickles them. The word tickle is a popular part for composites in the German language. For example, Germans speak of nervenkitzel when something excites them enormously. In the case of nervenkitzel, the person moves between fear and enjoyment of that fear, just as in the case of tickling, the person presumably moves between fear of unexpected threat and enjoyment.
Function and task
The origin of tickle reflexes remains controversial to this day. Medical experts such as Leuba refer to the reflexes as purely protective reflexes. The body reacts with such protective reflexes to external stimuli that could be dangerous to humans. The mechanoreceptors on the human skin, for example, react to touch. On some areas of the skin, such as under the armpits, on the neck or on the feet, gentle touch is rarely if ever encountered in everyday life. Particularly in these areas, the touch receptors react violently to the tickle, as they are not used to this form of touch from everyday life. Pressure receptors in particular are activated when tickled. As a result, they send action potentials to the cerebellum, the anterior cingulate cortex, and the somatosensory cortex. The anterior cingulate cortex is responsible for processing pleasant information. The somatosensory cortex, in turn, processes all touch information. In the course of stimulus transmission, the neurotransmitter dopamine is released, which regulates feelings of happiness in particular. The tickling sensation therefore originates in the brain instead of on the skin. The action potentials of the skin sensory cells are answered by the brain at the end of the chain with the initiation of a weakening body reflex. Possibly, laughter in this context is an embarrassment gesture to appease the tickler. This theory is supported by the observation that people can tickle themselves only in very rare cases and in very few places. Other scientists assume a relief effect. Already Darwin’s theory to the tickling represented this assumption. So the unexpected touch would be equal to a big fright, because the brain does not know to estimate it at first. As soon as it turns out to be unthreatening, the relief effect occurs and in connection with it the laugh reflex. In studies, scientists used magnetic resonance imaging to observe the brain activity of tickled people and, based on the observational results, argued in favor of the relief theory. On the other hand, prolonged tickling can also be perceived as torture. Therefore, in the Middle Ages, the feet of various people were tickled at the pillory as part of a torture technique. Some people also integrate tickling into their sex life. The goal of these practices is then usually the inhibition reduction in the tickled partner or simply the joy of laughing together through close touches.
Diseases and ailments
Tickle attacks can cause complaints in extreme cases. Especially lung and muscle pain sometimes occur as a result of convulsive laughter attacks. In extreme cases, convulsions and choking can also occur. Sometimes victims of extreme tickle attacks also complain of muscle ache-like symptoms the day after. If tickle attacks occur independently of tickle attacks, then various diseases may be responsible. Especially tickle attacks caused by irritated mechanoreceptors of the nose can occur in the course of persistent colds or even more frequently in the context of hay fever and other allergies.On the skin, irritations such as those caused by certain items of clothing or detergents are sometimes responsible for tickling sensations. In this case, however, the laugh reflex is usually absent and those affected would possibly rather speak of itching. The tickling sensation can be prevented in the context of damage to the central nervous system. Damaged mechanoreceptors then no longer report touch stimuli, for example, and tickle attacks can thus no longer be triggered. In the case of damage to the brain or the conduction pathways, the tickle stimulus may sometimes no longer be transmitted to consciousness or may be transmitted only slowly. In such a case, there may be talk of a sensitivity disorder. These complaints may be due to mental illnesses. However, they can also be associated with diseases of the nervous system, such as multiple sclerosis. Hypersensitive mechanoreceptors can also have disease value. For example, tickling could be experienced as severe pain. Possibly, in this context, the mere air on the skin also tickles. In this context, there is also talk of a sensitivity disorder.