You Can’t Tickle Yourself, And Scientists Think They Know Why

Dragging fingers across one’s own ribs usually produces pressure or an itch, not the squirming jolt another person can set off with the same move. Researchers have chased the reason for decades, and the leading answer lies in how the brain handles touch it causes itself.

Part of the puzzle is that “tickle” covers two different sensations. One is light, feathery knismesis, the itchy tingle of an insect crawling on the skin, which people can largely produce on themselves. Another is gargalesis, the laughter-inducing tickle from strong, repetitive pressure on places like the armpits, sides and soles of the feet. A 2025 review in Science Advances says that second kind is hard to self-induce.

Four papers published over nearly three decades show how far the leading explanation reaches, and where it still falls short.

Why Can’t People Tickle Themselves?

Most likely because the brain predicts its own touch. When a person moves on purpose, the brain uses a copy of the movement command to forecast where and when touch will land. Researchers call this setup a forward model. Touch that matches the forecast feels weaker, an effect called somatosensory attenuation. Touch the brain didn’t see coming gets no such discount.

An early brain-scanning test came from Sarah-Jayne Blakemore, Daniel Wolpert and Chris Frith in London. In a 1998 Nature Neuroscience study, six healthy volunteers lay in an MRI scanner while a piece of soft foam brushed their left palm. Sometimes they moved the foam themselves with their right hand, and sometimes an experimenter moved it. A main touch-processing area called the somatosensory cortex was more active when someone else did the brushing. Part of the cerebellum, at the back of the brain, quieted down when a participant’s own movement produced the expected touch. It did not quiet down when the same movement touched nothing.

Blakemore’s team read that pattern as a sign that the cerebellum helps predict what movements will feel like. With only six people, the study was small, and it used light foam strokes on the palm. Researchers now class light palm strokes like these as knismesis, not laughter-producing tickling. A brain scan of this kind also cannot show that the cerebellum does the job alone.

Can Practice Make Self-Tickling Work?

Partly, at least in the lab. In a 2019 eLife study, Konstantina Kilteni and colleagues at Karolinska Institutet in Stockholm had 30 participants tap a sensor with their right index finger. Each tap triggered a tap on their left index finger, either right away or 100 milliseconds (a tenth of a second) later. Participants first went through 500 of these trials, then judged how strong the taps felt.

After practicing with the delay, the delayed tap felt weaker and the instant tap felt stronger than after practice with no delay, suggesting participants’ expectation had shifted to the later moment. A follow-up experiment in the same paper found the shift grew with more practice.

A separate group of 30 people tested ticklishness. Each person moved one robot’s arm with their right hand. A second robot copied that motion and stroked their left forearm with a sponge-covered tip, either right away or 150 milliseconds later. After practice with no delay, people picked the delayed stroke as the more ticklish one about 73% of the time on average. After practice with the delay, that fell to about 65%, so the instant stroke now felt relatively more ticklish. That change was modest and only narrowly passed the study’s statistical test.

Kilteni’s team wrote that the result suggests people can learn to tickle themselves. These were robotic strokes and finger taps, not the hands-on tickling that makes people laugh. Researchers also said their data could not show whether the brain adjusted its existing prediction or learned a second one, though they leaned toward the first.

Does Real Tickling Fit The Same Explanation?

Less neatly. A 2022 study in Philosophical Transactions of the Royal Society B, led by Sandra Proelss with Shimpei Ishiyama and Michael Brecht, tested hands-on tickling in 12 adults who came in pairs so that each person knew their tickler. Participants were recruited from the research team and its members’ social circles, and one person’s data were dropped because of recording problems. Each person was tickled on the neck, armpit, side of the trunk and sole of the foot, while cameras, a breathing belt and a microphone tracked reactions and participants rated each tickle.

Reactions came fast. Chest movements and joyful expressions appeared about 300 milliseconds after a tickle began, and laughter followed about 200 milliseconds later. When participants made tickling motions on themselves while their partner tickled them, they rated the tickle as weaker, and their laughter started later and happened less often. Touching their own skin dampened ratings more than making the tickling motion without contact.

Proelss and colleagues suggested that self-tickle suppression may come from a broad dampening of sensory signals that arrive at the same moment, and they questioned whether the precise, timed prediction described above is needed. By their own account, that idea doesn’t fully explain why the no-contact motion also helped. With so few participants, all drawn from one research group’s social circle, the study cannot say how well these results hold across ages, cultures or relationships.

Does The Evidence Explain Self-Tickling?

Partly. In her 2025 Science Advances review, Kilteni writes that researchers broadly agree that dampening predicted self-touch is the most likely reason people can’t tickle themselves. She also points out that every brain-imaging study of self-tickling so far used non-ticklish presses and taps, or light palm strokes that produce knismesis. Experiments with real, laughter-producing tickling are still needed to settle the question.

Lab studies consistently show that self-caused touch feels weaker than touch from someone else, and one lab has shown the brain’s timing forecast can be retrained with practice. Still unproven is whether the same brain machinery explains the squirming, laughing kind of tickle.

By the leading account, a rib poke that produces only pressure is the brain recognizing its own handiwork. Each failed self-tickle offers a small view of the nervous system sorting sensations into self and other, a sorting job science has yet to fully explain for the kind of tickle that makes people laugh.