In Comes the Kiss (The Neuroscience of a DFMO)

Of the many surprising novelties that freshmen face as they embark on their four years of college, the dance floor make-out (DFMO), may come as a particularly intriguing shock. In a university social setting, one can see the appeal of making out with a random stranger — having some casual fun with no strings attached — but there are still some puzzling practical questions. How does the make-out start? Who makes the first move, and when? On a typical night out at the street, a DFMO is a relatively common sighting. But surprised yelps and angry slaps across the face are relatively uncommon. Do couples have some sort of secret signaling that enables this smooth transition from grinding to making out?

Yes. There is some signaling, but it’s not so secret — neuroscience, along with some clever evolutionary adaptations, provides a very clear explanation. This explanation comes from research into the coding of peripersonal space done by Professor Michael Graziano’s lab in the psychology department at Princeton University. Though its current studies focus on consciousness, Professor Graziano’s lab has also made huge strides in the neuronal understanding of space-perception and movement. His recently published article in Aeon, “The First Smile,”1 focuses on the smile through evolutionary history to explain the fascinating parallels between defensive and social movements. And it is this study of defensive movements that provides a thorough scientific understanding of the logistics of the DFMO.

It all starts with defense neurons, types of neurons involved in coding peripersonal space: the space immediately around our body. There are groups of these neurons that code for different regions, firing if something enters their particular “bubble.” Their firing sends a signal to the brain as part of a defense mechanism to initiate protection from some new stimulus. This evidently important system extends far back into evolutionary history; if an animal notices an approaching predator, it needs a defensive mechanism. And the magnitude of its response depends on whether the predator is a few feet or a few inches away, whether it’s lurking or charging and whether it’s heading toward the foot or toward the jugular. To use a modern analogy, a beach ball lazily coming toward a person’s arm might induce a small response — a slight jerk inward of the arms — while a baseball toward the head would induce a full-blown reaction: whole-body cringe to protect the abdomen, arms raised up to block a blow, shrugged shoulders to shield the neck and windpipe and scrunched cheeks to build protective wrinkles of skin around the eyes.

This defensive mechanism has been conserved over evolutionary history, but the ability to interpret its presence in others appears more recently. The fact that humans and higher order primates have developed this ability implies an adaptive advantage. Because the strength of defensive responses can indicate varying levels of nervousness or fear, an individual who is able to detect these responses and notice how they change over time can gain insight into her relationships with others.

Similarly, the lack of a defensive response also holds valuable information: it indicates social comfort and invitation. This is the key to the DFMO. Consider, for example, a group of girls casually dancing when a stranger musters up enough courage to start grinding with one of them. Assuming he comes up behind her, the spatial “bubbles” he approaches aren’t as vulnerable as the ones in front of her face or chest. The extensive physical proximity involved in grinding, though, is enough to alarm defensive neurons and initiate a response. If she doesn’t respond defensively, he detects this suppression of a reaction and interprets it as encouragement. Over the next few minutes, hands might start to wander and torsos might squeeze closer to increase the amount of physical touch, and at every step the lack of defensive response serves as encouragement.

Something else, however, is necessary to initiate the transition from grinding to making out. Since physical proximity has reached its maximum, it must logically involve spatial “bubbles” adjacent to more vulnerable parts of the body — and that’s exactly what both experiential and scientific evidence corroborate.

The lack of a defensive response also holds valuable information: it indicates social comfort and invitation. This is the key to the DFMO.

A junior girl well-practiced in the DFMO has found a move that works all the time: she reaches around with one hand and gently brushes her hair over to one shoulder, thereby slightly turning her head and exposing her neck. Now girls are known to constantly adjust their hair — shaking it back, flipping it this way, adjusting it that way — but here the hair is merely an excuse to turn the head and expose the neck. In the context of defensive mechanisms, the signals sent by this move are undeniable; exposing the neck is a direct reversal of a typical response to defend one of the most vulnerable areas of the body.

As Graziano aptly explains, “flaunting the side of your throat where the jugular runs sends an unconscious signal of invitation. It says: I’m letting my guard down so you can get close.”

The mystery is explained and the secret signal is solved. The DFMO is no longer a college novelty; its nuances can be explained by neuroscientific findings. So tilt that head, flaunt that neck and bam: in comes the kiss.


About The Author

Hi! I'm a Molecular Biology major planning on getting certificates in Quantitative and Computational Biology (QCB) and Neuroscience. I'm in the Integrated Science Curriculum here at Princeton, and work in a Neuroscience lab on campus. I'm also in the Chapel Choir, on the board of the Episcopal Church at Princeton (ECP), and on the club running team. And, of course, I write for Innovation! The best science magazine on campus.