For all the laughter it produces, sometimes being ticklish is just annoying. It has prevented me from truly enjoying pedicures and far too many back massage attempts have ended with me in a fit of giggles. Try as I might to fight it and take the focus off my jumpy nerve endings, the slightest brush against a certain spot is enough to make me squirm and laugh uncontrollably.
Why are we ticklish in the first place? Is it an inherited trait passed down from our ancestors or is it a learned social act? And why is it that we laugh, despite our discomfort?
A Physiological and Social Phenomenon
When it comes to the question of why certain parts of our bodies—feet, chest, lower backs, underarms, etc.—are more sensitive than others, some believe that it’s an evolutionary trait we’ve developed to protect ourselves from small bugs, spiders, and other surprise attackers. The key word here is surprise—the grazing touch usually needs to come unexpectedly to yield laughter. Research has shown that the cerebellum, which registers touch, shows more activity when the touch is a surprise rather than anticipated. If the brain recognizes that the touch is coming, it will make the nerve response less intense, which is why we can’t tickle ourselves successfully.
Why we laugh when tickled is possibly where social cues come into play. Tickling that produces laughter is referred to as gargalesis, a term coined by two psychologists, Arthur Allin and G. Stanley Hall. (They differentiate this type of tickling from knismesis, which is akin to a light itch.) Gargalesis usually only occurs when the tickler and the tickler’s “victim” are familiar and comfortable with each other. A child being tickled by his or her parent, or a person being tickled by a partner or close friend, will often attempt to escape the attack, but will laugh when doing so. However, imagine if a random person on the street or even someone you just met tried to tickle you. The response would probably not be laughter—in fact, it would be downright awkward and creepy. That’s because we learn from a young age that it’s only socially acceptable for those we trust to have that kind of contact with us.
What’s so Funny?
Charles Darwin believed that tickling was the key to creating social bonds between people, such as mother and child or between romantic partners. He saw it as social play, a positive and safe way to stimulate each other. But is tickling actually pleasurable? Even though we laugh along when the right person performs the act, tickling is not often enjoyed. The discomfort makes us wiggle away from the person, yet our laughing encourages the tickler to continue. In one study that examined the physical response to tickling, 70 to 75 percent of participants laughed when stimulated, but most stated afterward that they generally did not enjoy being tickled. If that’s the case, where does the laughter come from?
Theories about the origins of tickling-induced laughter abound. One psychiatrist, Donald W. Black, found that the places on our bodies most prone to feeling ticklish relate to our reflexes, implying a connection between the playful fighting back that occurs during tickle fests and acquiring necessary self-defense skills. According to him, laughing reinforces the act as a safe, non-harmful way of learning how to protect oneself. There are also some personality theorists who postulate that laughing, and even the degree to which we are ticklish, is based on how anxious or jumpy we are as people. They believe that those who are more prone to anxiety tend to have the most uncontrolled reactions to tickling, and that even the anticipation alone can set them off.
However, one study conducted at the University of San Diego challenged these social hypotheses. Researchers created a tickle machine to test whether participants would have the same reaction to a non-human tickling sensation, and many ended up having similar responses—laughing, twitching uncontrollably—to those tickled by another person. Another study also found that rats similarly laugh when tickled, implying that the laughter might be reflexive, at least initially, rather than socially learned.
Our common response to tickling may start out as a physiological reaction to perceived threats, but there is no doubt that it serves a social function as we get older. Despite the fact that tickling makes us cringe, it has a playful connotation. However, anyone who has suffered a merciless tickle attack at the hands of an older sibling knows that it isn’t always about being playful—sometimes it’s just a way to get under someone’s skin. Other times it happens without intention, like during a routine pedicure.
Regardless of the role tickling plays in our lives, whether it protects us or brings us closer to others, we can always count on it as a sure source of laughter—even if we’re not sure why.