We (pretty much) all do it: close our eyes while we're kissing someone. It's not because our partner is a hideous troll or a repulsive monster, so why do we do it?

Why do people close their eyes when kissing?

A study on vision and tactile sensory experience found that people close their eyes while kissing to allow the brain to focus on the task at hand. Our brains find the sensory process difficult while concentrating on visual stimuli.

The study, led by Dr. Sandra Murphy and Dr. Polly Dalton of Royal Holloway, University of London, was published in the Journal of Experimental Psychology: Human Perception and Performance. Their kissing findings occurred without studying people kissing. But the study explains our inability to properly and simultaneously process visual and sensory stimuli.

In other words, your brain, even subconsciously, wouldn't be able to enjoy eating a cupcake while gazing at a beautiful flower at the same time.

The researchers asked participants to perform a letter search task of either low or high difficulty, as well as respond to the presence or absence of a brief vibration delivered at the same time to either the right or left hand. The sensitivity to the obvious tactile stimulus was reduced when doing the more challenging visual search task.

"It was already known that increasing the demands of a visual task could reduce noticing of visual and auditory stimuli," said Dr. Murphy. "Our research extends this finding to the sense of touch."

When kissing and engaging in other activities enjoyable to our sense of touch — such as slow dancing — people want to focus on the touch, rather than the potentially distracting sensory experiences.

"These results could explain why we close our eyes when we want to focus attention on another sense," Dr. Dalton said. "Shutting out the visual input leaves more mental resources to focus on other aspects of our experience."

"Passionate kissing causes our blood vessels to dilate and our brains receive an increase in oxygen. As our heart rate increases, our breathing becomes irregular, our cheeks flush and our pulse quickens. The pupils in the eyes dilate, which is one reason why we may close our eyes.

"Kissing also ignites a mix of positive neurotransmitters, including endorphins dopamine, serotonin, adrenaline, and the 'love hormone,' oxytocin," says Dr. Ava Cadell, an AASECT Certified Sex Counselor with Doctorates in Human Behavior and Human Sexuality.

Dilated pupils also cause us to become more sensitive to light and potentially experience dizziness, which could also explain why we close our eyes when kissing.

Maybe that's why they call it swooning?

Either way, close your eyes, pucker up, and just enjoy the experience!