When touch turns to tickle
Touch is a powerful sensation that can trigger both physical and emotional reactions. One such reaction to touch is the tickling sensation. The word tickling actually refers to two different phenomena, knismesis and gargalesis. Both of these are communicated to the brain by the millions of nerve endings that sit beneath our skin.
Knismesis and Gargalesis
Knismesis is the tickling feeling you get when something is lightly touching your skin causing an itchy sensation. Take for example a bug crawling on your skin, you feel a tickle and as a reflex itch the area. Knismesis makes sense, it’s a protective reflex to stop you from being bitten by bugs and spiders. It is widespread in mammals; horses whip their tail when they feel a fly on their back and a dog will twitch its ears if it feels a light touch.
Gargalesis, on the other hand, is the type of ticklishness that makes you involuntarily LOL- laugh out loud. It’s the type you thought about when you read the title, the type that makes you twist and squirm and contort your body to avoid. Unlike knismesis this type of ticklishness is experienced in very few animals; when you tickle a chimp, they exhibit laugh like breathing, rats, penguins, owls and meerkats also exhibit a laugh like response to being tickled. This type of tickling is caused by light to moderate pressure being applied to certain sensitive areas such as the neck, ribs, inner thighs or feet. Anyone who has been tickled can attest to the fact that too much pressure causes it to go from pleasurable to painful. A group in Germany studied the difference between ticklish laughter and voluntary laughter using fMRI imaging, only tickling laughter activated the hypothalamus (responsible for involuntary reactions) and areas of the brain that are responsible for pain anticipation.
Why do we laugh when we are tickled?
These aforementioned sensitive areas are those that are vulnerable if we were being attacked. This has led to the theory that tickling may be an evolutionary mechanism for teaching us how to protect ourselves, just like puppies play fight, being tickled allows us to learn to protect ourselves as we squirm and kick to try and evade the person tickling us. This also explains why we can’ tickle ourselves. You can’t ‘attack’ yourself as you would be able to predict it. Activity in the cerebellum in fMRI studies supports this idea. The cerebellum is responsible for a process known as sensory attenuation; whereby the brain filters out irrelevant information to concentrate on the more important stuff. The cerebellum can anticipate the tickling touch and so when you try to tickle yourself you can’t. Interestingly, some people with schizophrenia can tickle themselves, believed to be due to brain changes that disable their ability to differentiate self-initiated actions. But this still doesn’t tell us why we laugh when we are tickled. Well, imagine if you tickled someone and they started crying and screaming, most people wouldn’t continue, so the theory has come about that the laughing is to encourage tickling and the self-defence training that comes with it.
Is there a way to stop yourself from laughing? Some people believe that you can utilise your bodies sensory attenuation ability by simply placing your hands on top of those who are tickling you. This will help your brain anticipate the tickle and hence better suppress the tickle response, that or you scream and cry and hope the person stops. Either way, the urge is pretty hard to suppress, best to embrace it and take it as training for any future zombie apocalypses