Columns / Discourse / April 13, 2011

The Neuroscience of: Making out

Have you ever thought about kissing? Like how completely weird it is? Deconstruct it for a minute: two people pressing their heads together with the focal point being their lips. As if it couldn’t get any weirder, they put each other’s tongues in their mouth.

Now think of the conversations you’ve had with friends about kissing. There are sloppy kissers, snake-like kissers, fast kissers, hard kissers and there’s love-at-first-kiss. A kiss can make or break the future of an entire relationship—so much pressure placed on the kiss! So here’s a run down of structures, chemicals and brain regions involved in locking lips.

Playing tonsil hockey is a sensory overload for your brain. Your blood vessels dilate allowing for more oxygen to the brain than normal. You get all those butterflies (amygdala); deep breaths (adrenaline); heart racing (also adrenaline); pupils dilating (norepinephrine). If merely kissing is this much of a fast-paced rush, it’s no surprise old people have heart attacks because of sex.

So why do we do it? What would kissing allow you to do with your potential partner? Well, subconsciously it allows you a chance to sample their genetics. I say subconsciously because no one really thinks to themselves, “That last chromosome just doesn’t taste right, I better get outta here”; and yet that’s exactly what your brain does, through upwards of 10,000 taste buds. Cranial nerve #7 (two-thirds of your tongue) is the biggest pipeline of information for taste.

At the same time as this genetic buffet you are also taking in your make-out buddy’s scent through cranial nerve #1 (it’s right in your nose.) It picks up all those smells of your lover and takes them right up to the anterior olfactory cortex (smell region), a section of your prosencephalon (hand on your forehead go in an inch – you’re in the general area).

But no one kisses with their body pulled away. You’re all up on your sweetheart! Hands going left and right, up and down, in and out. “Aa-fibers” are the fastest ones in the body, and they are responsible for your sense of proprioception (stick your hand out; if you had no proprioception you probably wouldn’t be able to find your hand to begin with). And all the while the somatosensory cortex (pointer finger, go to the top center of your head and each way left and right is the general area) has been getting most of this activity, and it’s sizing up your beau’s genetics from the smell, taste, touch and looks.

So it’s the end of the date and time to decide “Ask them up to your room, or kick ’em to the curb?” If your subconscious is pleased, then you probably have had a strong release of the neurotransmitter dopamine into the nucleus accumbens (point in between your eyes and drill till you hit something soft). And it’s just like drugs! Cocaine, heroine, LSD; that love-at-first-kiss might as well be love-at-first-toke. Dopamine helps you take the next step with that adult playmate. And provided this make-out session wasn’t just a one-night stand, as you mac on each other more often oxytocin is generated (linked to feelings of “love” and attachment).

We all know not all of them are winners, and bad kisses really piss your brain off. Cortisol is a known stress hormone and is released when you feel like that person was trying to eat you alive and you gotta get the hell out of there.

But no matter how much you love or hate the kiss, that moment is unforgettable. Not because it sent chills down your spine or made you want to puke but because you made so many neural connections (smell, tastes, touch, sound). And just one of those cues could send you into a delightful daydream… or wave of regret.

Gabe Paz

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