Kissing is one of the most basic forms of human affection. While this behavior is ingrained within us, one unique feature involves closing our eyes while we do it. It seems strange, but it also feels completely natural. Why do we do this?

There is some science behind all this.

It has to do with the biological functions involved in kissing. Some anthropologists believe that kissing actually comes from “kiss feeding,” where a mother feeds her child by pre-chewing their food. Others just believe that this in an instinctual behavior.

Two women about to kiss, covered in xmas lights
Sharon McCutcheon on Unsplash

Regardless of how it started, we know that humans have been doing it for a long time. The first record instance of kissing in literature actually dates back 3,500 years. It’s found in Sumerian poetry, Sumer being one of the first urban civilizations in history. It’s also found in ancient Egyptian writing, ancient Indian writing, and ancient Jewish texts.

It’s been written about for so long because it actually serves an important function in choosing a romantic partner. Kissing shows how compatible you are with the other person. You pick up each other’s pheromones when you kiss, which will either attract you further to the person or repel you.

Man and woman kissing, with wind blowing the woman's hair
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It seems like with so much information being passed during a kiss, you’d want to keep your eyes open to see what’s happening. But as anyone who’s ever opened their eyes during a kiss will tell you, it feels very, very strange. Why is that?

Keep ’em closed!

Psychologists once thought that it was because the eyes could not properly focus on something as close as the other person’s face. That caused us to close our eyes because we couldn’t really see what we were looking at. We know now that this theory is incorrect.

Man kissing woman on her forehead
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It’s actually because it’s extremely difficult for our brains to focus on tactile and visual sensations at the same time. Our brains are processing the tactile function of the kiss and focusing all its energy on that. When we open our eyes, we overload it with information in such a way that it doesn’t know what to focus on. By keeping our eyes closed, we allow the brain to focus on what’s important.

Keeping our eyes closed also heightens the sensation of kissing. Because our brain is totally focused on the touching going on between our lips, we get more sensation from that kissing, which is a pleasurable feeling.

Older couple kissing outdoors
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The idea that your brain can’t process visual and tactile responses at the same time is proven in other ways. It’s the same reason you may not feel your phone vibrating in your pocket when you’re talking to your friend. You’re so focused on that conversation that you simply don’t notice the vibration of the phone.

Many of us instinctively close our eyes when we’re focused on tactile sensation, even though we may not realize it. Psychologists know this is an ingrained behavior because blind people often close their eyes while reading braille. Even though their sight is limited (or non-existent) they close their eyes to focus on their fingers.

Two dogs kissing in front of a lake at sunset
Patrick Hendry on Unsplash

So it turns out that it’s not a strange behavior at all. Instead, it allows us to fully enjoy the kiss without the distractions caused by our eyes.