The science of why we are ticklish

HostWe have all been there, someone pokes you in the ribs and suddenly you're a mess of laughs and kicks. It's such a strange thing because it's not always a good time. Sometimes it's actually kind of stressful. Why did we end up with this odd way of acting when someone touches us?

GuestIt's a bit of a puzzle, but we can look at it in two ways. There are actually two different kinds of tickling. One is that light, itchy feeling, like when a bug crawls on your arm. That one is simple. It's a warning to look down and see what's on you so you can brush it off. But the heavy kind, the kind that makes you laugh and squirm when someone pokes your sides, that's much more interesting. It's tied into how we get along with others and how we learn to protect ourselves.

HostBut why can't I do it to myself? I can jab my own ribs as much as I want and I don't feel a thing.

GuestYour brain is basically a machine that tries to guess what's coming next. When you move your own arm to touch your ribs, your brain already knows exactly what's about to happen. It sends a message to the rest of your head saying, don't worry, this is just us. Because it can see the touch coming, it dials down the feeling. It's the same reason you don't notice the weight of your own clothes or the way your feet feel in your shoes. But when someone else does it, it's a total surprise. Your brain can't guess the timing or how hard the poke will be, so it lets the full signal through. That lack of control is what makes the feeling so strong.

HostIf someone is poking a spot that makes me squirm, why am I laughing? It feels like the wrong signal to send if I want them to stop.

GuestThat laugh is a bit of a social trick. Most of the time, the people who tickle us are friends or family. It's a very close, personal thing. By laughing, you're showing that you know it's just a game and you're not being hurt. It's a way to keep the play going without things getting too serious. If you just got angry or hit the person, the friendship might suffer. The laughter keeps the mood light while your body is reacting to a very heavy touch. It's like a sign that says, I'm having fun, but also please be careful.

HostBut it still feels like I'm trying to fight them off. My whole body is trying to block my sides and twist away.

GuestThat's because it's a way to practice. Think about where you're ticklish. It's almost always the soft spots like the neck, the stomach, and the ribs where your most important parts are hidden. In a real fight, those are the spots you have to guard at all costs. When a parent tickles a child, it's like a safe version of a fight. The child learns how to block and move to protect those weak spots. They're building the ways of moving they would need to stay safe in a real scrap, but they're doing it in a way that feels like fun. It's training for life, hidden inside a joke.

HostSome people really hate it, though. For them, it's not a joke at all.

GuestThat's the big catch. Even though we laugh, the body is actually under quite a bit of stress. Your heart beats faster and you can't catch your breath. For some, that loss of control is just too much. Since you can't do it to yourself, you're stuck until the other person decides to stop. If you don't trust the person, the laugh stops being about fun and starts being a way your body just acts that you can't shut off. It's a very thin line between a good time and a bad one because your body is acting like it's under attack even if your head knows you're safe.

HostCan we ever learn to shut it off?

GuestIt's nearly impossible because it's such a deep, old part of how we're made. Even apes do it. Young chimps make a specific panting sound when they play that's just like our laugh. It's a built-in part of being an animal that lives in a group. One thing that sometimes works is to put your own hand on top of the person's hand while they tickle you. It tricks your brain into thinking you're the one doing the moving, which can dial down how much it hits you. But for the most part, you're just stuck with how your brain handles a surprise.

HostIt's wild to think this is a lesson in how to stay alive.

GuestOne big question that's still out there's whether the laugh means we're actually happy or if our bodies are just pulling a fast one on us.

HostThose soft spots on our sides are much more than just a place to get poked during a joke.