It's true — laughter is the best medicine. In an instant it can improve mood, increase energy, decrease pain and reduce stress. Yet for such a powerful healing tool, scientists know very little about it. Neuroscientist Sophie Scott from the University College London’s Institute of Cognitive Neuroscience has spent a good deal of her career studying laughter and has come to the conclusion that much of what we think we know about laughter is wrong.

In a recent TED talk, "Why We Laugh," Scott often gets the giggles when she explains the science of laughter and fills us in on what's really happening with each chuckle and guffaw. Here are some fun facts from the video and from her many interviews that you probably never knew about laughter.

1. Couples who laugh together stay together.

In her TED talk, Scott describes an experiment conducted by psychophysiologist Robert Levinsen in which the scientist brought married couples into the lab and monitored their physical responses to stressful conversations, Levinsen found that the couples who managed that stress with laughter immediately became less stressed as indicated by their physical responses. The couples who laughed together were also more likely to report high levels of satisfaction with each other and stay together longer.

2. Laughter may increase your threshold for pain.

Anthropologist and psychologist Robin Dunbar conducted a number of experiments both in the lab and in the field and found that a person's pain tolerance is higher after laughter than it was before or in the absence of laughter. He suggests that the body's release of endorphins during laughter may help create an "opiate effect," that decreases the sensation of pain. So the next time you find yourself inappropriately laughing at those treadmill fail videos, just console yourself with the knowledge that you are actually trying to help those hapless souls feel less pain.

3. Real laughter never comes through the nose

Man laughing hysterically When you get the serious giggles, it's not something you can control. (Photo: Sergey Furtaev/Shutterstock)

Scott describes two kinds of laughter — involuntary laughter and posed, or social laughter. As its name implies, involuntary laughter is not something you choose to do but is rather a helpless response to a situation. Involuntary laughter is longer and higher-pitched than voluntary laughter and it comes from the belly and not the nose. Posed or social laughter is something that we choose to do as a way to communicate with someone that we like them or maybe even love them. It's more controlled, but it's still laughter. And both are important tools that humans use to communicate.

4. Laughter is the most universally recognized emotion around the world.

Scott conducted an experiment in Namibia in which she asked indigenous Namibians and English people living in the country to listen to recordings of people expressing various moods — fear, anger, surprise, disgust, sadness, happiness, relief, triumph, and contentment, and rate the emotion. She found that laughter — and thus happiness — was the most easily recognizable emotion of the lot. "Almost immediately, it started to look different from the other positive emotions," Scott said in an interview with BBC News.

5. Laughter is a measure of the strength of a relationship.

It's not just couples who benefit from laughter. Scott found that all relationships in a social network benefit from the giggles. That backs up studies that found that laughter in the workplace builds a happier work environment, boosting a company's bottom line. Researchers noted when coworkers regularly share laughs, team performance increases both immediately and several years later.

6. You are 30 times more likely to laugh if you're with someone else.

Laughter is contagious — quite possibly the most contagious human emotion. That's why you laugh at a joke when your friends are laughing, even if you missed the punch line. Or why that comedy seemed so much funnier when you watched it in a crowded theater than when you watched it by yourself at home. It's also why it's hard to keep a straight face when you simply hear others laughing, even if you have no idea what they are laughing about. (And if you haven't seen a group of babies contagiously laughing, well, there isn't a sound quite like it. Check out the video above.)

7. Laughter is more like an animal call than speech.

Researchers used to think that laughter was a strictly human activity, but Scott notes that all mammals laugh. Sometimes the laughter is associated with tickling and sometimes it's associated with play, but it's almost always associated with social interactions. Scott suggests that laughter is more closely related to animals calls than it is to human speech. She describes laughter as an ancient evolutionary tactic utilized by mammals that helps improve mood and strengthen social bonds.