Fragrant Fraternizing: What Do Our Pheromones Tell Us?

pheromone party

Last week, friends of mine threw a pheromone party. “How often do we stop and appreciate each others’ odor? … Not Often Enough!!!” they proposed. We were invited to hang out and “identify our friends who have sparkling personalities, and those who just have an interesting musk.”

As a sucker for anything with the stench of pop sci, I was game. I had read about pheromone parties last year, when they caught on with rapid-fire popularity in cities like New York and Los Angeles. An artist named Judith Prays threw the first pheromone party three years ago in New York City. She deemed it a success: of the 40 singles who participated in the inaugural event, 12 “hooked up,” with half of those pairs developing into relationships. (Of the first two parties Judith threw—one in Brooklyn and one in L.A.—the longest resulting relationship she knew of lasted six months.)

Prays was inspired by the first relationship that she had pursued based purely on physical attraction—a love of two years that she regarded as the most significant relationship of her life. What she couldn’t get over was how much she enjoyed her then-partner’s smell: “even when he smelled objectively nasty, I thought it smelled good.”

Prays wanted her pheromone parties to challenge the cerebral, analytical entanglement that often characterizes dating—stripping attraction down, instead, to basic chemistry (literally). The parties were like an antithesis to online dating, which seemed to be all about judging others based on meticulously-crafted self-advertisements. I liked this idea of getting out of my own prefrontal cortex: not overthinking it; seeing what my instincts had to say about my attractions.

This is how the party worked: in the midst of a New England heat wave, we were given identical white T-shirts. To play, we had to wear/ sleep in these shirts for at least three days. (I wasn’t able to find how or why Prays chose three days, but that’s become the general guideline for these parties.) Come time for pheromone exchanging, we placed our smelly shirts in numbered bags and threw all the bags into a big pile in the center of the room. Nobody knew anyone else’s assigned number, only their own (in science, this is called a “double-blind” study because both the participants and administrators of the study are “blind” to whose bag is whose).

Let the smelling begin! We party-goers sat cross-legged, passing bags back and forth and jotting down notes. Like wine tasters, we have to resort to abstract descriptors of the shirts we sample. To keep track of odors, we scribbled notes like “Grandpa’s old Rolex,” “BBQ/ hickory,” “food co-op,” “wet attic,” “vanilla sky” and “yeah yeah yeah.” One person’s shirt smelled like “apple pie” in one armpit and “crayon wax” in the other. Another shirt prompted a, “I don’t like this, but I’m sure you’re nice.” Some shirts were perceived in wildly different ways, like one shirt described as both “dead person” and “sugar and spice.” Others were eerily similar—a friend and I respectively reviewed the same shirt as “Thai food / marker” and “garlic / Sharpie” without consulting one other; another shirt was nearly unanimously characterized as “potato chips.”

Through all this, I couldn’t help wondering how much we were actually picking up on each other’s pheromones and how much we were just noting the overt smells of deodorant, fragrances and food lifting off the shirts. How much of this was actual science and how much just hipster pastime? It occurred to me how little I actually knew about pheromones. Aren’t they odorless? How do we actually detect them? What role do they play in our lives, if any?

Turns out, scientists are just as confused.

Pheromones are chemical signals that trigger changes in behavior or physiology among members of the same species. While pheromones serve an assortment of functions—marking territories, forming aggregations, warning others of danger, attracting mates and laying down trails—they are generally thought to be mutually beneficial to both sender and receiver.

Discussing pheromones in humans is where it starts to get a bit murky. In fact, it’s hard to say if human pheromones even exist in the conventional sense. The strongest evidence of their existence is the syncing of menstruation cycles. If we want to find other clues, perhaps the best place to start is with a vestigial structure in our bodies: the vomeronasal organ, or VNO.

The VNO is shrouded in public fascination and controversy because its very existence has historically been linked to this unresolved question of whether or not humans send and receive pheromones. In animals with a functioning VNO, the organ is part of the accessory olfactory system and contains sensory neurons that detect chemical stimuli. Perhaps you can recall images of animals—including cats, horses, deer—with their lips flared backward? This behavior is called the Flehmen response: when an animal enacts the response, it curls its upper lip back and inhales to help waft pheromones into the VNO located above the roof of the mouth. For the most part, the VNO is used to detect pheromones, but it can also serve other functions. For example, snakes probably use their VNOs to track prey.

A stallion exhibits the Flehmen response.

A stallion exhibits the Flehmen response.

We know for sure that the VNO is present in human embryos. The question is whether, like our tails, they retract as we mature in the womb. Efforts to find the adult VNO have been all over the place, with reported prevalence ranging from 6% to 100%, length estimates ranging from 2-62 mm and varying descriptions of basic location and structure. Part of the problem is that many investigators try to identify the VNO by its opening rather than the tubular structure itself.

Among primates, the VNO is functional in strepsirrhines (i.e. lemurs, pottos and lorises). In humans and chimpanzees, it appears vestigial. One of the biggest arguments for the non-functionality of the VNO is that we don’t have evidence of any active sensory neurons in the VNO or nerve connections between the VNO and the brain. Moreover, the genes that participate in VNO function in other mammals are defunct in humans.

The displacement of a functional VNO in higher primates might have to do with changes in facial growth patterns. Human faces, for instance, grow downward relative to that of other primates. Furthermore, overlaps in function between the VNO and our main olfactory system might have rendered the VNO superfluous.

Most of the evidence for a functional human VNO comes from research conducted in the 1990s by a group led by Luis Monti-Bloch, a neurophysiologist. The researchers reported that the VNO could detect steroids, which they termed “vomeropherins.” These steroids, they claimed, produced gender-specific changes in physiology including hormone secretion, heart and respiratory rate, mood, brain activity, skin conductivity and body temperature. Curiously enough, funding for their research came partially from a corporation that makes personal care products containing these very steroids. Their results have never been not been successfully replicated (hmmm…).

So, for now, our knowledge of all-things-VNO is still pretty hazy. In general, it seems that our sociosexual lives are not as highly governed by chemistry as that of other mammals… or, at least, it’s not as immediately obvious to what extent they are. A thought that is perhaps liberating?

In the end, though it’s doubtful our pheromone experiment served much function beyond providing a trendy guise for social congregation, it opened the door for new styles of interaction. The pheromones theme provided an excuse to play: an opportunity that seems harder and harder to come by as I age. As I engaged with people in ways I otherwise wouldn’t have, I felt liberated. An evening spent making new friends? I’d call that an evening well spent.

Portions of this essay appeared in a piece called Vestigia, published in the College Hill Independent on October 4, 2013.

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