What is hilarious to do to others, unbearable when they do it to you and you cannot do to yourself? Give yourself a gold star if you guessed ‘tickle’. 

Most of us, from a very early age, are familiar with tickling but from the beginning of human history scientific minds from ancient Greek philosopher Aristotle to modern day researchers have been challenged with the question: Why are we ticklish?

There are actually two types of tickles: 

Knismesis is the sensation you get on your skin similar to when you feel a feather run along your arm. This irritating feeling makes you want to brush away whatever is touching you. 

Gargalesis is the type of tickling that happens when someone digs their fingers into your ribs or other ticklish spot and makes you laugh uncontrollably. 

Most of us cannot tickle ourselves because our brains anticipate the sensation. Scientists believe people with schizophrenic traits can tickle themselves, as it is unlikely they can tell the action is voluntary.

Tickling may have initially played a part in human evolution as a tool to teach children to defend themselves. Our ticklish spots tend to be our most vulnerable ones, like our stomachs or necks. When someone tickles us we are compelled to protect those areas as if we are facing a threat. In fact, when scientists look at the brain of someone being tickled they see that the hypothalamus, the part of the brain that is responsible for our ‘fight or flight’ response, is stimulated. 

So why laugh if we are under attack? Some researchers have suggested that laughter acts as a defense mechanism. It indicates to the ‘attacker’ that we submit to the tickling in an effort to stop any further tickles.

Laughter might also be a learned response. Tickling is a form of social bonding and one of the earliest interactions between parent and child. Happy play between the two often involves smiling and laughter and when tickling is introduced the child associates the activity with the response. This social development is taken one step further as it becomes a way that children play and interact with each other. 

This theory is also backed up by the fact that tickling is mood-dependent. Biologist Charles Darwin observed that children tickled by a stranger would scream rather than laugh.

Regardless of why we are we are ticklish for most of us tickling is actually physically rewarding. It causes laughter for both the tickled and the tickler and laughter releases a chemical called dopamine that produces feelings of happiness. Laughter truly is the best medicine.

Research into the science of tickling is not limited to human subjects. Primates, such as chimpanzees, have aided in the study of laughter. When engaged in the rough and tumble play associated with tickling, the chimps vocalized with a panting sound or ‘ha-ha’ that indicated they were playing and not attacking. Even rats have served as good study participants. In one such study rats recognized the big tickling hand as a playmate and ‘giggled’ as they chased it.

Article originally published in Brainspace Magazine Spring 2018