Ask anyone and they can attest to the fact that of all the things we feel like doing when someone tickles us, laughing is probably one of the last on the list. Even if you don’t find being tickled downright unpleasant, you probably still feel that the sensation gets old pretty quick. Yet, tickles make us squeal and giggle in a parody of actual enjoyment – why?
First, let’s talk about what tickling is. There are two kinds of tickling: gargalesis and knismesis. Gargalesis is rough tickling that results in outbursts of laughter, and is usually centralized to ticklish areas like the feet and armpits. Knismesis is a lighter sensation and doesn’t tend to result in laughter, but rather produces an itchy sensation.
Your skin is full of nerve endings that are highly sensitive; they need to be, in order for you to be able to survive without constantly hurting yourself. When these nerve endings are stimulated, signals shoot from the nerve endings up to your brain. fMRI scans have helped researchers learn that tickling activates two main centers of the brain: the somatosensory cortex and the anterior cingulated cortex. The former analyzes touch, while the latter is responsible for feelings of pleasure.
When you start laughing as a result of tickling, the Rolandic Operculum is activated; this same area is also activated when you’re laughing at a funny joke. The Rolandic Operculum operates a bevy of functions like emotional reactions, vocal reactions, and facial expressions. However, laughter that is caused by being tickled also causes the hypothalamus to kick in – the hypothalamus is your adrenaline center, the home of the flight-or-fight response. It’s also associated with pain anticipation, when your body prepares to experience physical pain.
The involvement of the hypothalamus is probably the most interesting lead in the great tickling mystery; it’s possible that laughing while being tickled is actually a way to signal that you are submissive to an attacker – this also provides a neat explanation as to why we sometimes burst out laughing before our tickler has even touched us. But, according to some neuroscientists like Robert Provine, tickling is also an important bonding activity that grows the bond between mothers and their offspring. Furthermore, humans aren’t the only animals to engage in tickling and who laugh at being tickled: both great apes and rats are known to giggle when being tickled.
Fun fact: it’s impossible to tickle yourself; because your brain is too smart to surprise itself.