How people interpret touch can vary by background, but the areas on the body where people feel ticklish were found to be consistent across cultures.Credit: d3sign/Getty
Ticklishness is a distinct, specialized body sensation, and how people experience it seems to be consistent across cultures, two neuroscientists have found. The study, published on 10 August in Nature Human Behaviour1, lays the groundwork for standardized, systematic research into tickling.
Humans are not the only ticklish animals: other great apes tickle each other, and rats and meerkats (Suricata suricatta) respond to tickling by humans — suggesting that the sensation has been preserved across evolution. Known as gargalesis, the kind of tickling used in the study is associated with play and involves using strong, repetitive pressure to elicit laughter and squirming. A different type of tickling, known as knismesis, uses a feather-light touch and doesn’t trigger laughter. Knismesis has attracted research attention because of its similarity to itching, a feature of several medical conditions, says Ziliang Xiong, a neuroscientist at Radboud University in Nijmegen, the Netherlands, and first author of the study.
But for a long time, gargalesis was taken seriously only by a few scientists, and as a result, it is “really a very poorly understood sensation,” says Michael Brecht, a neuroscientist at Humboldt University in Berlin who studies ticklishness in rats and in humans.
To find out more, Xiong and his Radboud colleague Konstantina Kilteni recruited 448 participants from three distinct cultural backgrounds: Dutch, Greek and Chinese. Each person completed a survey about their experiences and perceptions of tickling. Then, on a computer, each participant coloured in areas of a body model to create maps of where they were ticklish, repeating the exercise for other body sensations, such as pain or pleasurable touch.
Almost all participants (98.4%) reported having experienced tickling, and 95.8% reported having tickled someone else. Experiences were similar across all three cultures tested. This might not sound surprising, but studies suggest that how people interpret touch that is processed emotionally, such as hugging, can differ by cultural background, says Kilteni.
What’s more, ticklish areas were highly consistent between cultures and individuals, featuring the neck, armpits, belly and soles of the feet. Comparisons with maps of other sensations, such as pain or pleasure, suggested that the sensation is decidedly distinct and unique. “Ticklishness seems to be its own class, physiologically and psychologically,” says Xiong. “It doesn’t seem that it is only a by-product or the integration of other body sensations.”
