In the fourth century BCE, Aristotle wrote in Parts of Animals that “the fact that human beings only are susceptible to tickling is due (1) to the fineness of their skin and (2) to their being the only creatures that laugh.” Although this ancient theory misses the mark, it lies at the beginning of a long tradition of philosophers and scientists questioning the nature of tickling. Thinkers such as René Descartes, Baruch Spinoza, Galileo, and Charles Darwin have provided their own theories about this weird autonomic response. Yet despite 2,500 years of investigating the matter, scientists still aren’t sure why it’s impossible to tickle yourself.
A few theories about the nature of tickling have grown out of this legacy of scholarship. One idea is that tickling is a form of parental bonding, while another posits that it’s a warning mechanism to protect sensitive areas of our bodies from potential injury. We’ve also learned that there are actually two types of tickling: knismesis and gargalesis. Knismesis occurs when something light brushes across your skin, which is something you can induce by yourself. However, gargalesis — that uncontrollable funny-but-not-funny tickle — can only be triggered by another person. Why? Well, basically, your brain knows a tickle is coming when you do it to yourself, which in turn suppresses its response. Evidence from brain scans show that the somatosensory cortex and the anterior cingulate cortex, which process touch and happy things, respectively, are more stimulated when tickled by someone else compared to ourselves. The only exception to this biological rule is people with schizophrenia, because they often can’t differentiate between self and external touch. Even though tickling usually induces a smile, just remember that those “happy feelings” during a tickle are actually part of an uncontrollable defense mechanism, not genuine laughter. So please — practice safe and consensual tickling.
Media Release/InterestingFacts.com
