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  • Hey, Vsauce, Michael here.

  • Attachment of two people's lips kissing. The average person will spend about 20,160 minutes

  • of his, or her, life kissing. And the world record for the longest, continuous kiss is

  • 58 hours, 35 minutes, and 58 seconds. But why do we kiss?

  • I mean, if you think about it, it seems kind of weird...right? I mean, sure, today kissing

  • represents peace, respect, passion, love. But, when the first two people in human history

  • kissed, were they just kind of being gross? Well, let's begin with what we do know: kissing

  • feels good, and it's good for you.

  • A passionate kiss burns about 2-3 calories per minute, and releases epinephryn and norepinephryn

  • into the blood, making your heart pump faster. Kissing, more often, is correlated with a

  • reduction of bad cholesteral and perceived stress- but, these positive effects didn't

  • become widespread by accident. Why did brains and bodies that love kissing become so common?

  • Well, a popular story holds it that Pacman's shape was inspired by the shape of a pizza

  • with a slice missing. But Toru Iwatani, the creator of Pacman, admitted that this was

  • only half-true. Pacman's shape was also inspired by rounding out the shape of the Japanese

  • character for "mouth." And it's mouths and Pacman's favorite activity, eating, which

  • again bring us closer to the heart of the kiss.

  • Evolutionary psychologists have argued that what we know today as "kissing" may have come

  • from "kiss-feeding": the exchange of pre-chewed food from one mouth to another. Mother birds

  • are famous for doing this, and many primates are frequently seen doing it as well. Not

  • that long ago, it was common between human mothers and their children. In fact, before

  • commercially produced, or DIY, baby-food instructions were readily available, it made a lot of sense.

  • Recently, Alicia Silverstone uploaded a clip of herself mouth feeding her child. It seemed

  • strange to some people, but even though, yeah, it exchanges saliva, which, like any contact

  • with an infant, can transfer pathogens, healthy mothers and healthy children can benefit from

  • the fact that kiss feeding provides nutrients: Carbohydrates, proteins, iron, and zinc, which

  • are not always available in breast milk. Plus, an adult saliva can help pre-digest the food,

  • making vitamins like B-12 easier for the baby to absorb.

  • So, mouth-to-mouth attachment has a history of intimacy, trust, and closeness. Your saliva

  • also carries information about who you are, your level of health, and, mucus membranes

  • in our mouth are permeable to hormones like testosterone, making a kiss a way to taste-test

  • a potential mate. A good kiss can be biological evidence that your kisser might be a good

  • mate.

  • So, as a strategy for mate selection, pre-historic people who enjoyed kissing, and did it more

  • often, may have made better decisions, picked better mates, reproduced more successfully,

  • and, eventually, become the norm- giving us...us. People who love kissing.

  • Any infant could have seen those benefits coming from a mile away, even though an infant's

  • vision isn't that great. From birth to four months, babies can only focus on things about

  • 8-10 inches away from their face which, not surpisingly, is about the distance to their

  • mothers face while breast feeding.

  • So, faces, especially those looking right at us, tend to be the very first things in

  • our lives we can focus on and see clearly. This might explain why we are so good at detecting

  • faces. Humans are off the charts when it comes to this, in fact, we tend to see faces even

  • when there aren't any- it's called "pareidolia."

  • Because humans are so cooperative, it makes sense for us to be good at recognizing faces.

  • And, more importantly, detecting when someone is looking directly at us and clearly expressing

  • when we are looking at someone else.

  • A predator who lives by not being seen needs a gaze that's less obvious. In fact, research

  • has shown that our surprisingly white sclera's, the area that borders the iris, isn't just

  • an accident, but is a vital piece of human eye morphology that makes it easier for us

  • to ascertain the direction of someone else's gaze at a glance.

  • We also have impressive gaze-direction networks inside our brains containing individual neurons

  • that fire when someone is staring directly at us, but that stop firing if that gaze shifts

  • just a degree or two.

  • So, yeah, you can tell when you're being watched, we humans are quite sensitive to it, even

  • those of us with "Scopophobia": the fear of being stared at. But, to be sure, in order

  • for this to work, the other person's gaze must be within your line of sight- your field

  • of vision- that is, you can see them. Otherwise, if the stare is coming, say, from behind,

  • there is no evidence that people can tell they are being watched.

  • The "Psychic Staring Effect" falls within the realm of pseudo-science. No widely-accepted

  • studies have ever found evidence that it exists. Anecdotally, what's more likely is that the

  • very act of rubber-necking to see who's watching causes people to look up, and for your gazes

  • to attach.

  • But, what about attachment when no one is watching? One explanation for an infant's

  • love- attachment to their mother- doesn't involve vision or staring, but, instead, food.

  • The idea is that we love our mother's because as soon as we are born, they are a source

  • of life-sustaining nourishment. But, what if that nourishment came not from a loving

  • mother, but from a scary "Wire Mother"?

  • In the 1950's, Harry Harlow conducted a series of famous, but controversial, experiments

  • on monkeys at the University of Wisconsin, Madison. Harlow's findings had substantial

  • implications on our understanding of attachment. But, by today's standards, his work would

  • largely be considered unethical. In one of his most famous experiments, Harlow separated

  • young monkeys from their mothers as soon as they were born and stuck them in cages with

  • two fake mothers: a soft one wrapped in cloth that did nothing, and a cold, mechanical mother

  • made of wire that, nonetheless, did provide food. But, despite being a cupboard mother,

  • the young baby monkey's didn't bond with her. When Harlow and his team scared the baby monkeys

  • with a strange contraption, the monkeys ran and clinged not to their wire source of life-sustaining

  • nourishment, but to the soft, cuddly, and otherwise useless cloth-mother.

  • This suggested that warmth and comfort was more important than food when it came to nurturing

  • attachment. Harlow also built a rejecting mother which used a blast of pressurized air

  • to push baby monkeys away. But, instead of finding another source of comfort, these monkeys

  • clung even tighter at all times than monkeys raised without rejecting mothers. And this

  • is what blows my mind: the instinct for warmth and comfort in newborn creatures is so strong

  • it not only resists attempts to frustrate it, but is paradoxically strengthened by it.

  • Eckhard Hess tested this by using electric shocks to discourage ducklings from following

  • the object they were imprinted on. But, it only strengthened the behavior and made them

  • follow more closely than ever before. The fact that a "wire mother," or a rejecting

  • mother, or receiving electric shocks for attaching to your mother, would cause more attachment,

  • more love, more dependence, seems like a paradox. But, paradoxes can teach us. As Oscar Wilde

  • put it, "a paradox is the truth standing on its head to attract attention."

  • And what gets our attention here is the effect uncertainty can have.

  • In 1955 A.E. Fisher conducted an experiment on puppies. His team separated puppies into

  • three groups. Members of the first group were treated kindly every time they approached

  • a researcher. Members of the second group were punished for approaching the researchers.

  • And puppies in the third group were randomly treated kindly, or punished. They grew up

  • never knowing what to expect. Their world was not a world of kindness or punishment,

  • but rather, one of uncertainty.

  • What's really chilling is that the study found that that group, the third group of puppies,

  • wound up being the most attached to the researchers. The third group loved the researchers the

  • strongest and was the most dependent upon them. Guy Murchie called this the "Polarity

  • Principle": "stress, including the mental stress of uncertainty, in an ingredient in

  • attachment or love and perhaps even manifestations of hatred (its polar opposite) somehow enhance

  • love."

  • Uncertainty, psychologically, can lead to some of the greatest feelings of attachment

  • and dependence. Good things, and bad things, in our lives often seem random and out of

  • our control. So, it's no surprise that we often react with blind love and acceptance

  • in the face of an unfair existence because, what else are we supposed to do? We are that

  • third group of puppies.

  • But, investigating uncertainty, conquering it so as to make the best decisions possible

  • is advantageous. So, over time, life has favored activities that turn uncertainty into knowledge.

  • Not every person out there is the best mate for you, but if it didn't matter which one

  • you picked, a kiss, a taste-test, wouldn't be necessary, and it wouldn't need to feel

  • so good or bring us so much pleasure.

  • So, go out there and kiss someone today. And, as always, thanks for watching.

  • By the way, tomorrow I am headed to the European Space Agency's Space Port in South America

  • with Euronews to watch a rocket launch in real life. Do you have any questions about

  • space or space travel today? Let me know in the comments below and I will ask the experts

  • your questions.

Hey, Vsauce, Michael here.

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