Why is laughter contagious? Blame your brain.
Popular Science...
I still remember the time I was sitting in class when the teacher asked me to read a passage out loud. Just seconds before, some classmates had started giggling about something, and it was contagious. As I read aloud, I tried to stay serious, but kept dissolving into fits of laughter. I knew our strict, no-nonsense teacher would not be impressed, but I couldn’t stop.
You’ve probably been there, too: laughing when you’re not supposed to, trying to hold it in, and somehow that only making it worse. So why is laughter so hard to control?
Laughter is not completely under your control
Research suggests that there are two kinds of laughs: helpless, involuntary laughter (like the kind I was experiencing in that class) and polite, social laughter (like when your friend tells a joke and you laugh because you like your friend, not because the joke is funny).
Different parts of the brain drive each type of laughter. Voluntary laughter stems from areas of your brain that control movement. When you force yourself to laugh, you are essentially switching on these parts of your brain.
Meanwhile, parts of the brain that deal with emotions, like the amygdala, which are not under conscious control, trigger involuntary laughter. This kind of laughter can start before your thinking brain has time to say, “Wait, this is not a good moment.”
Involuntary laughter shouldn’t be confused with a rare neurological condition called pseudobulbar affect where people suddenly laugh or cry without meaning to. In the 2019 film Joker, this disorder inspires the unexplained laughing fits of the film’s titular character, Arthur Fleck (played by Joaquin Phoenix).
“Ordinary laughter, even when it feels difficult to suppress, is still a normal emotional and social response: It is usually connected to amusement, context, and interaction,” explains Dr. Anne Schacht, a professor of cognition, emotion and behavior at Göttingen University’s Institute of Psychology.
“Pseudobulbar affect, by contrast, is a neurological condition in which people experience sudden, involuntary episodes of laughing or crying that may be exaggerated or may not match how they actually feel.”
What makes laughter “contagious”
Have you noticed that things seem funnier when you’re with friends or family? Scientists say laughter is strongly linked to social situations. In fact, we are about 30 times more likely to laugh when we are with someone else than when we are alone.
A recent study suggests that the socially contagious nature of laughter is one of the reasons why it’s so hard to control. Researchers at the University of Göttingen in Germany investigated how laughter can be controlled. Volunteers listened to jokes while scientists measured tiny movements in their face muscles—movements so small you normally can’t see them. The volunteers tried different tricks to stop laughing, like distracting themselves, keeping a straight face, or telling themselves the joke wasn’t that funny.
Some tricks worked a little, but there was a catch. When the volunteers heard another person laughing, it became much harder to stay serious. The sound of laughter acted like a signal to the brain saying, “Hey, this is funny! Join in!”
“Our research suggests that laughter can feel hard to control because it is not just a deliberate response to something funny,” says study co-author Dr. Schacht. “It is also a fast, partly automatic social reaction that is strongly shaped by other people.”
Laughter feels good, so why stop?
Another reason laughter is hard to stop is that your brain actually rewards you for doing it. Research shows that when people laugh together, the brain releases natural feel-good chemicals called endogenous opioids.
These chemicals—including but not limited to endorphins—have a host of beneficial effects. They reduce pain, create an intense feeling of well-being, help you withstand stress, protect your heart, and also regulate your appetite.
Because laughter feels good, your brain doesn’t like to shut it off once it starts. That’s great at a party, but not so great when you’re supposed to be reading out loud in front of the class.
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Trying not to laugh can make it worse
The results of Dr. Schacht’s study showed that distracting yourself, controlling your facial muscles, and rethinking how funny the joke or situation is can help you hold back laughter. “Yet even these strategies reached their limits in certain social settings,” Dr. Schacht says.
But sometimes forcing yourself to stop laughing can actually backfire.
In another study, people were told to suppress certain thoughts or behaviors. When they tried not to think about something, they ended up thinking about it more later. The same thing happened with laughter. People who tried hard not to laugh often laughed even more afterward. Scientists call this a “rebound effect.”
The bottom line
Your emotions, your brain’s reward system, your muscles, and the people around you all contribute to uncontrollable laughter. It’s a combination of factors working together, “rather than a single switch in the brain,” says Dr. Schacht.
So the next time you start laughing at the wrong moment—during class, in a meeting, or when someone tells you to be quiet—remember: your brain is built this way.
And honestly, that’s probably a good thing. Life would be pretty boring if we could always keep a straight face.
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