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Ahhh! Where I live, it’s that magical time of year again: Snow is falling!

It’s cold outside. Roads are icy. It’s dark by like mid-afternoon.

I guess now that I think about it, not my fave. But that doesn’t mean there aren’t other reasons to be happy this time of year. Science makes me happy.

Snuggling in and watching videos makes me feel all cozy. So, let’s explore the science of happiness. Let’s start with love and chemistry.

Here’s Michael explaining why Valentine’s Day should be less about hearts and more about your brain. It’s February, which means, at least here in the the U. S, your eyeballs are getting accosted by a barrage of red and pink heart-shaped lovey-dovey stuff.

Now, I don’t want to rain on anyone’s Valentine’s Day, but this is bogus for a few reasons. One, our hearts look nothing like those symbols, and two, our hearts have very little to do with how we actually feel love. So if you want to make a more accurate valentine, I suggest you cut that construction paper into the shape of a brain, or more specifically, the limbic system, or even more specifically, the hypothalamus.

See, the limbic system is the emotional center of your brain. It guides your emotional, motivational, and reward processes, and basically makes you feel all the feels, from pleasure to fear to anger. It also influences some of your biological rhythms, like sex drive.

Nerve receptors all over your body send sensory stimuli, say, the sound of a loved one’s voice, or the feeling of a hug, to the limbic system, where it eventually gets forwarded to the hypothalamus . Perched on top of your brain stem, this small but mighty bit of brain is your body’s visceral ground control, overseeing your entire autonomic nervous system, meaning it’s in charge of processes you don’t consciously control, like blood pressure, digestion, and heart rate. It’s basically the boss of all the bosses: the CEO of your body.

When it comes to love and other feels, the hypothalamus uses those autonomic pathways to cause physical responses to match your emotions, like how the sight of a secret love can leave you sweat-soaked, with a heart that feels like it’s going to jump out of your chest. In the same way, someone who’s heartbroken may experience their emotional stress in a very visceral way, for example, through heartburn, high blood pressure, or changes in sleep and appetite. Guided by your hypothalamus, your autonomic nervous system also influences the skeletal muscle system that lets you pull off facial expressions and posturing.

So when it comes to communicating emotions, from “back off” to “come hither,” that’s your hypothalamus talking. And, it influences your endocrine system, which uses hormones to make your body do and feel all sorts of things, including, probably, love. For one thing, it controls your pituitary, the master gland that then manages most of the other endocrine glands in your body, as well as the hormones they release.

That covers everything from your stress and excitement response to your libido. But the hypothalamus also makes a few special hormones of its own, like oxytocin, the famous “cuddle hormone,” which is involved in social bonding, among other things. So in the end, if you want to get real about love, toss out the heart and start saying “I Hypothalamus You.” I just hypothalamus that guy.

I should tell him that. Better yet, I should show him! If only I had a tail and could wag it to show him he makes me happy.

Maybe I’ll just tell him. But tail wagging, while it can be a sign of happiness, is much more subtle and communicative than I originally thought. Here’s Olivia unpacking some of the research into why dogs wag their tails.

As cute as it would be, dogs can’t talk, and their faces aren’t as expressive as ours, so it’s sometimes hard to tell what they’re thinking. But dogs do communicate in one way we can’t: with their tails. Those fluffy tails are constantly conveying your dog’s mood, but just because she’s wagging it all over the place doesn’t always mean your dog is excited to see you.

A tail wag doesn’t always signal happiness and friendliness. It’s way more complicated than that. The exact behavior can vary depending on the breed of dog, but the general pattern is the same.

If your dog lowers their tail between their legs, it probably means they’re scared, anxious, or submissive. If they hold it up, something has captured their interest, like a squirrel! The higher the tail, the more aggressive the dog is feeling, although the relative height varies between breeds.

Some dogs just naturally hold their tails higher than others. If their tail wags slowly, your dog is maybe a little uncertain about the situation. But if it’s waving energetically from side to side, it’s probably exactly what you think: a happy, enthusiastic hello.

As strange as it sounds, a pair of studies by a group of Italian researchers showed that which direction a dog wags its tail is important, too. In the first experiment, 30 dogs were exposed to four different stimuli: their owners, strange humans, a dominant unfamiliar dog, and a cat. The dogs wagged their tails much more on the ride side of their bodies when they saw their owner, and slightly more on the right when they saw a strange human.

They also tended to wag on the right when they saw a cat, but the movements were smaller and more insecure. But when they saw a dominant, strange dog, they wagged more on the left side of their bodies. According to the scientists, this means they wagged on the right when they saw things they’d like to approach, and on the left when they saw things they’d want to avoid.

See, the two sides of dogs’ brains have different specialties. The researchers suggested that one side handles approach responses, like when a dog greets its owner, and the other side handles withdraw responses. And which way the tail waved seemed to depend on which half of the brain was being activated.

A follow-up study with about 40 dogs showed that other dogs could actually pick up on this. When they saw a video of another dog wagging its tail on the left, they got anxious, and their heart rates went up. But when they watched a video of a dog wagging its tail on the right, they stayed relaxed.

It’s possible that this is a way dogs communicate with each other, since many of them have easily-visible tails. So if you want to become an expert dog whisperer, keep a close eye on that tail. It could be telling you more than you’ve ever realized!

What a cool job: to be a researcher who studies what dogs’ tails are telling us. Another fun job would be a gelotologist, someone who studies laughing. Just like tail wags, our laughter can be a lot more complicated than just thinking something is funny.

In this video, Hank explains the physiology, psychology, and sociology of why we laugh. Hey, you know what’s funny? Why people laugh.

Laughter is a physiological response that involves at least fifteen facial muscles, the respiratory system, the brain’s limbic system, and, if the joke is really good, even your tear ducts. But laughter doesn’t always indicate happy times. It can actually be a sign that something is seriously wrong with your brain.

Gelastic seizures, or uncontrollable and random laughter or crying, can indicate the presence of brain tumors, or other conditions like pseudobulbar affect, a neurological syndrome that can affect stroke and brain-trauma survivors and M. S. patients. These conditions are sometimes called emotional incontinence because the sufferer can’t control these outbursts, which often have no root in how they’re actually feeling.

And how we feel, especially in groups, seems to be what laughing is all about. Some laugh researchers, and yes they are things, known as gelotologists, think much of our laughter is rooted in strengthening social bonds. We’re much more likely to laugh in a group than we are alone, and we tend to laugh more easily around friends and family.

That shared experience brings us closer, makes us feel part of a group. We also laugh to express relief, or to ease our nerves in stressful moments. Researchers theorize that there are a few specific reasons for laughing.

First there’s the incongruity theory, which maintains that it’s the element of surprise that triggers laughter, whether it’s an unexpected punch line or your friend tripping on a throw rug. Say you’ve been watching people walk through a room all day. Your brain registers this as predictable and boring behavior.

Then your friend walks in, trips on a rug, and drops a big box of ping pong balls. Once you’re sure your friend hasn’t, say, fallen on a bag of rusty knives, you find the fall hilarious because it was sudden and unexpected, and incongruous to the string of people you’d seen safely walking by. And because: ping pong balls.

Babies and little kids go for this kind of laughter a lot. They think really simple, unexpected things are funny, like playing peak-a-boo for five consecutive hours or pretending a banana is a telephone. Now, if you are the one who just tripped on the throw rug, you’re much more likely to laugh in surprise if you see your friend laughing with you.

This goes back to that shared laughter as social bonding thing. You’re probably feeling pretty embarrassed and tense, but are also relieved you aren’t hurt. That is where the relief theory comes in.

Because laughing is like a mental mini-break. Your brain is constantly working, taking in all sorts of information and ordering the body around. Sometimes it just needs a happy surprise.

This is particularly handy in stressful moments. The whole Hollywood wisecrack in the middle of suspenseful scene phenomenon is predicated on this idea. When Han Solo is in mortal danger, he cracks a joke to lighten the mood.

He needs it, Chewie needs it, the audience at the edge of their seats need it. Humor helps us cope with stressful situations. It sort of recharges our brains to face the task at hand.

Scientists call this releasing cognitive energy. The rest of us call it comic relief. But, back to you tripping on that throw rug… if everyone in the room is laughing at you, and none of them are your friends, they may be proving the superiority theory of laughter.

It means they’re laughing at your misfortune, and it probably means they’re a bunch of jerkfaces. Superiority laughter still promotes bonding, in an us versus them kind of way, but it doesn’t show much good will. Teens make fun of their parents and lots of other people. (Okay….so do lots of adults… ) But our teen years are usually awkward and confusing, and superiority laughter may help ease some of that pain.

So simply put, we laugh hardest at what we know best, and at what stresses us out the most. And maybe that’s why it’s great for you, both physically and emotionally. It reduces the release of stress hormones that jack those fight-or-flight feelings.

It lowers your blood pressure and oxygenates your blood flow. It even increases your T-cell levels that help with immune response, and B-cells that produce antibodies. Plus, laughing 100 times is estimated to burn as many calories as a 15-minute bike ride.

So you see, laughter is not the best medicine, but it's not a bad medicine, either. Okay, now here’s something that... doesn’t make me laugh, but it does make me feel happy and relaxed and...tingly? ASMR, or Autonomous Sensory Meridian Response, is one of those phenomena that’s probably been around a long time, but it wasn’t until the existence of the internet that people started being able to compare notes about it and therefore study it.

In this next episode, Hank explains the still-pretty-new research into ASMR. And don’t worry, if ASMR is not your thing, Hank only whispers for about 5 or 6 seconds right at the beginning. And right at the end, but I’ll cut him off, I promise!

I’m gonna get real up close and personal for a sec, but bear with me. It’s for science. Oh, I see you’ve come in for a haircut.

Let me just get my scissors. Did you feel anything strange just now? Maybe some shivers down your spine, or a pleasant tingling sensation? ‘cause, if so, you’re probably one of those people who experience what’s known as ASMR, or Autonomous Sensory Meridian Response.

And according to research published in the online journal PeerJ, it’s a real thing! ASMR is, basically, the tingling sensation some people get in response to a stimulus. Over the last few years, it’s gotten more and more popular, with communities of hundreds of thousands of people forming around YouTube content designed to trigger that shivery feeling.

Often, the videos will involve some kind of consistent sound or visual, like whispering, softly crinkling paper, or repeated movements. Lots of them also incorporate personal attention and roleplay, a content creator giving a haircut to the person behind the camera, for example. But there are also plenty of people who don’t believe it’s real.

The weird thing is that because ASMR is so new, scientists don’t know much about it. But if hundreds of thousands of people say that they’re experiencing something, a biological thing that we didn’t even realize was a widespread phenomenon. Well, researchers are going to start investigating.

After all, that’s what researchers do. The first peer-reviewed study of ASMR was published in March by two psychologists from. Swansea University in the UK.

They wanted to do four things: define the ASMR sensation, figure out what causes it, explore the connection to similar unusual feelings, and find out if it really does help with depression and chronic pain. So the researchers surveyed 475 people online, all of whom said they were sensitive to ASMR, and asked them questions about YouTube videos, specifically. Most of the subjects described the feeling as a spreading tingling sensation, and 63 percent observed that it started in a particular place in their bodies, like their scalps or shoulders.

As for what induces ASMR, whispering was the most popular trigger, with three quarters of the participants choosing that option. The second-highest percentage was 69 percent of people, who said that personal attention triggered their ASMR. Other common causes included crisp sounds and slow or repetitive movements, though about half the participants needed a specific type of environment for the ASMR videos to work at all.

And while 98 percent of survey-takers used ASMR videos to help them relax, only 5 percent said they found them sexually stimulating. The researchers also wanted to see if people who feel ASMR are more likely to experience synesthesia, where senses and body parts get mixed up. A synesthete might describe it as hearing colors or smelling music, for example. 5.9 percent of the participants did seem to have some degree of synesthesia, which the team confirmed in follow-up interviews.

But that wasn’t a significantly higher percentage than in the general population, where about 4.4 percent of people have it. To learn more about ASMR’s effects on mood, depression, and pain, they analyzed subjects’ depression risk of their subject with popular tests for depression and anxiety. Then they asked the survey-takers whether they found that ASMR affected their mood, and eighty percent said yes.

Oddly enough, half of people said that it didn’t even matter whether they felt the tingling at the time, just watching the videos made them feel better. Participants then rated their mood on a scale of 0, worst thing that ever happened to you, to 100, happiest moment of your life, before, during, and at intervals up to three hours after an ASMR session, and a clear trend emerged. People’s moods were kind of meh before the session, much better during and immediately afterward, and then slid back down over the next few hours.

But among people who had high risk for depression, the average mood improvement was more than double the change for those who had low risk. And around half of the 91 people with chronic pain said that either ASMR did help with their pain, or that they weren’t sure. Among those people, the survey showed that the tingling really did ease their symptoms for at least those first three hours.

The researchers point out that there’s still a lot more to learn about ASMR, like its physiological effects. Some scientists have even suggested that the tingling feeling might be some kind of tiny seizure. They’re also curious about ASMR’s possible connection to synesthesia, as well as misophonia, which is basically the opposite of ASMR; when certain sounds, like heavy breathing or chewing loudly, make you want to punch a wall.

Okay, I promised I wouldn’t leave you with Hank whispering, so I have one more video to leave you with. This one is actually not about happiness, but it’s a fun example of one of the aspects of SciShow that makes me the happiest: you! I feel lucky that we have such an engaged audience that asks questions and demands answers.

I think that’s good for SciShow, but also good for the world. It pushes us all to learn and try new things. I’m being serious, and you’re going to think that I’m not once I tell you what this next video is about, but I am!

So please keep that in mind, as Hank explains what research we could find to answer the question, “Why do we have butt hair?” I hope it brings you joy. SciShow recently began producing its fifth year of content. Something that we are extremely proud of.

And we're also proud of the community that's grown around these videos. We've covered a lot of topics, both trivial and profound, and we worked very hard to capture both our fascination and excitement as well as our deep desire to always get things right. And over the last year, you may have noticed a comment on, we think, every - single - SciShow video, asking us one question.

We have ignored this question long enough, it is time we took it on. litojonny wants to know, why does he have hair around his anus? Well jonny, the reason we haven't answered you is because, you know, like despite the fact that everyone gets their own personal pocket sized supercomputer, and that we can send robots to Mars, and convert the entire face of a planet to human use, we still do not really know WHY humans have butt hair. And it may not surprise you to learn, that not a whole lot of research has been done on the "Why" part of this question about butt hair.

But a fair amount of study has gone into the medical problems that butt hair can cause. For example: Pilonidal Disease is a chronic skin infection caused by hairs that get embedded near the top of the butt crack, which, if you want to impress your doctor, you can describe by its technical name: the intergluteal cleft. So as the owner of the butt yourself, you probably know that butt hair does seem to have more downsides than upsides.

So given that, what, if any, purpose does it serve? Well there are a few theories out there and maybe some enterprising scientist out there, watching right now, can do some research on them. But here's what has been proposed.

Theory number 1: Butt hair exists, because there's just no significant evolutionary pressure against butt hair. Sure, it's sometimes inconvenient, and, depending on the moment in cultural history, it might be considered unsightly, but it appears, that butt hair has never been a significant reason for one human not to make babies with another human. It's important to keep in mind, that not every bit of our physiology needs an evolutionary purpose, so butt hair might just be another side effect of unintelligent design.

Theory number 2: Scent communication. Body odor definitely has a negative connotation in today's world, but there's little doubt that communication through scent has played an important role in the evolution of humans. After all, that likely why we have body hair in the same areas where we produce body odors.

The hair is there to hold onto sebaceous, or oily, secretions, that have their own smell, and are also consumed by bacteria, that create even more smells. Since we all produce different smell compounds, and all have our own microbiomes, each individual human actually smells different. And if our early human ancestors were anything like other animals, and they probably were, their personal smell probably helped with everything from broadcasting territorial rights to attracting mates.

Butt hair then may be just another way our oldest human ancestors enhanced their smell profiles. Theory number three: Friction. In addition to giving off smells, humans have also always done a great deal of walking and running.

And skin rubbing on skin (especially in areas where that skin may be moist and dirty), can cause irritation, rashes, and even serious, debilitating infection. It's even possible, that those sebaceous or waxy secretions, that help produce body odor, are held in place by body hairs to provide an added benefit, acting like a natural anti-chafing cream. Now this theory, of the ones that we have talked about, is most appealing to me, personally, but it's very difficult to test, because shaving, or otherwise removing butt hair, and then having someone run 20 miles on a treadmill, is not a good experimental design.

Because, there's no way to know, whether any irritation is caused by the lack of hair, or whatever technique was used to remove the hair. None of which sound fun to me. But I have come up with an alternative experimental design that I like quite a lot.

Just interviewing a few hundred runners about how much they need to worry about butt chafing, and then measure the density of their anal pelage, to see if there's any correlation between whether they chafe and how hirsute their buts are. Which is not an experiment that I want to to do personally. But if there's an expert out there, in anatomy and physiology, who is up for tackling this prickly problem, please, take it on.

And if you get any useful data, definitely let us, and litojonny, know, how it went. Thanks for watching and being curious about the world. I speak for the whole SciShow team when I say it’s our honor to make videos we think you’ll enjoy.

If you have questions or topics you want us to research, let us know in the comments of any video. We read them, and we love hearing your ideas. Thanks for watching.

I hypothalamus you. [♪ OUTRO].