Tickling can be a fun game, a temporary annoyance, or a deeply unpleasant experience, depending on a person’s tickle response.
People vary in how sensitive they are to tickling. Some people are only ticklish sometimes, while others are not ticklish at all.
Scientists have discussed the tickle response for hundreds of years, yet researchers are only just beginning to understand why some people are ticklish, and what purpose this strange response might serve.
Researchers do not fully understand why people are ticklish and what evolutionary benefit tickling might offer, although there are several possible explanations.
There are two types of tickling, with different causes:
- Knismesis is when a light skin irritation, such as a bug walking on the skin, triggers an urge to brush it away. Some believe this response may protect against insect bites. A person can tickle themselves in this way.
- Gargalesis is more intense tickling, the kind that causes people to laugh when someone repeatedly touches a sensitive area of the body. People cannot tickle themselves in this way.
Some people believe that the tickle response might be protective. The most ticklish body parts are also the most vulnerable, such as the abdomen and throat. An automatic reflex-like response to push away the cause of the tickle could help protect these sensitive areas.
Tickling may be a reflexive response. Some people do not enjoy being tickled, but it can still cause a laughter reflex. However, in the same way that a person may cry when cutting onions without necessarily feeling sad, laughter does not always indicate enjoyment.
In 2013, a group of scientists placed people in a brain scanner and then tickled their feet. They found that an area of the brain related to involuntary responses (the hypothalamus) was active when tickling generated laughter. This suggests that the tickle response is involuntary.
The authors also noticed that the brain might process tickling as a painful experience. It might explain why some people recoil in response to tickling, and why many tickling games involve chasing someone who is trying to get away.
Another 2013 fMRI study found that the brain responded differently depending on whether laughter resulted from tickling or from joking with friends. This supports the idea that ticklishness is a reflex-like response.
People are more ticklish when the tickling catches them by surprise. This might explain why people cannot tickle themselves.
A person’s awareness of their ticklishness might, therefore, affect how ticklish they are.
The tickle response partly depends on a person’s mood. People are often less ticklish if they are feeling sad or angry.
A person’s ticklishness also depends on who is tickling them. The tickling of a trusted friend is likely to elicit a stronger tickle response than that of a stranger.
Researchers do not know why some people are more ticklish than others. Some speculate that ticklishness might be genetic, but there is no conclusive research to support this theory.
Some people may be ticklish on certain parts of the body but not others. For instance, one person could be very ticklish on their feet, but not under their armpits.
Some people are more sensitive to touch than others, so skin sensitivity can play a role in how ticklish a person is. A person with a loss of feeling in a particular part of the body, or with desensitized nerves, would be less likely to experience the tickling response.
Tickling is not unique to humans, which indicates that it evolved to benefit both humans and other animals.
Other mammals, including apes and mice, also show signs of being ticklish. Apes play tickle games with one another and mice will chirp on tickling.
Babies do not respond to tickling with laughter until they are around 6 months old. Some researchers believe that babies only become ticklish when they learn that tickling should be funny.
However, laughter does not always indicate pleasure, and early research suggests that even when babies do not see tickling causing laughter in others, they still eventually laugh as a result of tickling.
If being ticklish is a reflex, there might not be much a person can do to prevent the sensation.
Tickling is more intense when it comes as a surprise, so people could place their hands on those of the tickler to try to reduce ticklishness. This would allow them to predict what the tickler is doing, and might even trick their brain into thinking they are tickling themselves.
Some people believe that they can desensitize themselves to tickling through repetition. People who are very ticklish can get people to tickle them for practice.
However, scientific research has not uncovered a specific strategy that will help people become less ticklish.
Though it is a nearly universal human experience, researchers still do not fully understand the tickle response. It does not seem to link to particular personality traits or physical attributes, although people with nerve damage or a decreased sensitivity to pain may not be ticklish.
People who suddenly lose their tickling reflex should see a doctor. A significant change in nervous system response could indicate a problem relating to the nerves.
Different people experience tickling in different ways, so while tickling can be fun for one person, it may be unpleasant for another, even if they still laugh as a reflex. Always ask a person for their consent before tickling them.