The Scientific Reason Humans Laugh

A chuckle, a chortle, a guffaw, a titter, a gut-buster — yep, we sure have lots of words for different types of laughs. There's the anxious, forced laugh deliberately employed to reduce tension in awkward or embarrassing situations. There's the piggish snort that makes others laugh, in turn. There's the villainous "mwah ha ha" laugh, preferably in an evil lair while stroking a purring white cat. With so many nuanced shades of laughter, it's safe to say that laughter isn't just an integral part of human life across the globe, but one that serves a lot more functions than a mere reaction to a humorous situation or statement.   

Babies, for instance, laugh before they can utter a single word. But babies aren't laughing at the clever wordplay of a politically-oriented talk show host; for them, it's endless peekaboo and tickling. As Upworthy says, there are even scientists whose entire field revolves around observing laughing babies. Some people think painful accidents are hilarious, like when somewhen falls off a skateboard. And if black-and-white movies are to be believed, physical gags like a pie in the face were once the height of comedy. 

With so many causes of laughter, how can we pinpoint a specific biological purpose? Animals might hold the clue. NPR reports that 65 species of animals exhibit laughter, including various birds and our close primate brethren, gorillas, chimpanzees, and orangutans. All of these animals are social by nature, and often exhibit laughter as a form of play.

The ultimate social glue

Taking into account all the myriad reasons why a person might laugh, personal tastes in comedy, and cultural differences in humor, there's one ultimate no-brainer reason that people laugh: to maintain social bonds. How Stuff Works cites anthropologist Mahadev Apte describing a "bonding-laughter-bonding" group dynamic that occurs amongst strangers and friends alike, where people laugh and grow closer, and then because they're closer laugh more. This kind of pattern becomes reinforced through peer pressure and social norms, as folks don't want to be left out of the group. In fact, laughter is so tied to group behavior that people are 30 times more likely to laugh when in a group, as WebMD cites Robert R. Provine, Ph.D., a behavioral neurobiologist at the University of Maryland. Smiling and talking, by contrast, only happen six and four times more in a group.

For animals as social as humans, many researchers believe that laughter is our lynchpin social behavior, like barking to a dog or singing to a bird. Most critically, it extinguishes the fight-or-flight response. Imagine roving through a natural habitat and coming across a band of other people. How do you know they're safe to deal with? Friendliness and laughter. It's almost impossible to laugh and feel aggressive at the same time. As anyone who's been in an argument can tell you, laughter turns rigid, tense bodies to mush. And for those who've passed through dangerous situations, it's a way to calm down and give the all-clear.

Spotting a fake

If laughter developed as a way to diffuse tense situations amongst early humans, that means that laughter exists more to tacitly control others than to cheer oneself up. On How Stuff Works, Dr. Robert R. Provine says that laughter is deployed by group leaders to regulate the emotional tenor of the group. In fact, socially dominant individuals — like a supervisor in the modern world — use laughter more than members of lower social rank. This means that laughter is also a way for individuals to signify status. Further to the point, speakers laugh a whopping 46% more than listeners, as Scientific American says. This indicates that laughter is less of a response to others and more of an attempt to direct the behavior of others from the top down. 

And yet, not any laughter will do. The best laughter is authentic laughter. In an article published by the Proceedings of the National Academy of Sciences (PNAS), researchers found that people can accurately tell just by listening which laughter comes from close friends rather than people who've just met; no body language, no visual cues, no conversation — just the laughter. This means that laughter is also a way to learn about the relationships of others in a group, and spot which individuals aren't totally integrated. That means it's an excellent way to spot a fake. It also means that people are more adept at discerning fake laughter than they are fake words.

Involuntary and voluntary laughter

Things get a bit more complicated when figuring out why humans laugh in a physiological and neurological sense. For such a seemingly simple and commonplace action, there's quite a bit going on in the brain that produces laughter as an output. Science ABC tells us that there are actually two types of laughter: involuntary and voluntary. Involuntary laughter involves a simple, reflexive reaction like a baby responding to being tickled. Sensory information only passes through the most basic parts of the brain: the thalamus (an information relay center), the amygdala (related to emotional processing), and the brain stem (connected to automatic response). By contrast, voluntary laughter activates the temporal lobe related to the intake and processing of information. This happens when your mind is deciding in the moment, more or less, whether or not to respond to stimuli with laughter.

But whether involuntary or voluntary, there's no denying that humans are built to laugh. Besides all the aforementioned psychological and neurological causes of laughter, and all the social complications underpinning laughter, people also laugh because people like doing what feels good. The simple act of laughing is enough to make someone want to laugh more. To the point, Mayo Clinic says that laughter released endorphins, stimulates the flow of oxygen and blood through the body, reduces one's heart rate, decreases blood pressure, and over time improves the immune system, elevates mood, and even reduces pain. Isn't that enough of a reason to laugh?