Why do people kiss?
Listen to the MP3 Audio: Why Do We Kiss_
TRANSCRIPT:
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 to 3 calories per minute, and releases epinephrine and norepinephrine into the blood making your heart to pump faster. Kissing more often is correlated with a reduction of bad cholesterol 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 Pac-Man’s shape was inspired by the shape of a pizza with a slice missing. But Toru Iwatani, the creator of Pac-Man, admitted that this was only half-true. Pac-Man’s shape was also inspired by rounding out the shape of the Japanese character for “mouth.” And it’s mouths and Pac-Man’s favorite activity, eating, which together 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 B12 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 mouths 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 to 10 inches away from their face which, not surprisingly, 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 scleras, 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 the 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 is 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 mothers 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.