Why Are People Ticklish? Interesting Theories Behind the Sensation

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Why Are We Ticklish? A Scientific Explanation filadendron - Getty Images

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Remember having knock-down-drag-out tickle fights as a kid? At the time, they seemed like a normal part of play. But for most adults, the thought of being tickled is annoying at best. And yet, it’s near impossible not to crack a smile if a perpetrator dares to enter tickle territory. This dichotomy helps researchers understand what little they know about ticklishness.

Meet the Expert: Xinzhong Dong, Ph.D., an assistant professor of neuroscience at the John Hopkins University School of Medicine whose research specializes in gentle touch, itch, and nerve injury.

Below, we get into the details that help answer the question: Why are we ticklish?

The two types of ticklishness

For research purposes, tickling is characterized by the action of tickling and the reaction it elicits. As established by psychologist G. Stanley Hall, there are two types: knismesis, a light, feathery touch likened to hair brushed over the skin, which rarely prompts laughter, and gargalesis, the heavy tickling responsible for a guttural, visceral tickle reaction.

According to Xinzhong Dong, Ph.D., an assistant professor of neuroscience at the John Hopkins University School of Medicine whose research specializes in gentle touch, itch, and nerve injury, both types of tickling are “mainly mediated by sensory nerves,” he says, which perceive the tickles and signal the brain to react. However, research shows that the intensity of said reaction is dependent on the ticklee’s mood. If they’re upset or anxious, they’re less likely to respond with laughter.

Why are we ticklish?

It’s difficult to pinpoint a purpose for ticklishness. “I don’t think people have a real conclusion,” Dong says. But there are quite a few, albeit incomplete, theories on why ticklishness exists.

It’s a defense mechanism

One theory says that the tickling response is evolutionary, because a version of it has been observed in primates. With that in mind, there’s thought that tickling could be used by caregivers to help children develop defense skills for survival. Children could be taught to portray laughter, rather than discomfort, as not to display weakness.

Another way of seeing it: Think of the feeling you get when you *think* a bug is crawling on your arm, Dong says. Fight or flight instantly sets in as a form of self-defense.

It’s used as social bonding

Tickling may help facilitate the bond between parent and child, because it usually involves both parties smiling and connecting, which creates a positive social interaction. However, this theory fails to explain why so many adults hate being tickled.

It helps us understand humor

Researchers Alan Fridlund and Jennifer Loftis proposed that the tickle reflex may be many babies’ first training in humor; that they mirror the laughter and smiles seen in the faces of ticklers. This may train them to laugh at other similar stimuli and develop their understanding for what’s considered funny.

It’s reflexive

Like Ivan Pavlov’s dogs, who salivated at the sound of a bell that was associated with food, humans may be conditioned to laugh when tickled because the tickler is always laughing. This may also explain why some people laugh and squirm preemptively at the threat of being tickled, before they’re ever even touched.

Why are there ticklish spots?

Both Dong and studies concur that the most common ticklish spots in humans are the soles of the feet, armpits, and ribcage, likely because there’s a higher density of sensory nerves in those areas, Dong says, making the stimulation more easily detected. But more research is needed to confirm that.

Why some people are more ticklish than others

Some people are physically more sensitive than others, or as Dong puts it: “Everyone has different nerve density.” He adds that genetics could also play a part in ticklishness.

Dong does, however, believe you can train yourself to be less ticklish. Essentially, it takes a concerted, in-the-moment effort. “Remain relaxed, focused, and controlled,” he recommends. And deep breathing through it can help, too, he adds.

Why we can’t tickle ourselves

It may seem obvious, but we can’t tickle ourselves because when we do, it’s predictable. And when we can foresee the sensation, it cancels out the laugh reaction, Dong says.

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