Korean ajumma — middle-aged women — are real-life superheroes. The instant a passenger rises from a seat at the back of a packed city bus, the ajumma launches her handbag across the aisle to claim the spot before anyone else can sit down. Through a single flying accessory, her personal territory has expanded by several meters. Every Korean ajumma, it seems, comes equipped with Inspector Gadget's extendable arm. But territory-claiming is hardly their monopoly. Gen-Z luxury shoppers line up their bags outside department-store boutiques for the early-morning "open run." Foodies collect numbered tickets under a merciless sun at the latest viral restaurant. Marking territory, it turns out, is not exclusively an animal behavior. Our personal space becomes the reference point for our fight-or-flight response and even functions as the baseline from which we calibrate our relationships with other people. But what could physical space possibly have to do with infidelity?
One Hundred Meters Before Meeting Her
There is a well-loved Korean pop song by Lee Sang-woo called "One Hundred Meters Before Meeting Her." One passage goes: "Her image, filling my mind, seems to draw closer with every step. Could that cloud up there be cotton candy? Should I jump up and try it? ... The road feels so much longer today. One hundred meters before the place where I meet her."
Having endured a long-distance relationship with my wife, I know this feeling in my bones. There are people in this world who feel close no matter the distance between them. Lovers press so tightly together that a sheet of paper could not slip between them. And then there are people who feel uncomfortable even at a generous remove — people you would rather keep at arm's length, or farther. A scientist once set out to study these invisible distances between people with the rigor normally reserved for physics.
His name was Edward T. Hall, an American cultural anthropologist. Hall proposed that human relationships operate across four distinct zones of distance. The first is intimate distance — the closest range, reserved for family and lovers. According to Hall, this is anything within forty-six centimeters, roughly eighteen inches. The second is personal distance — the space we maintain with close friends and trusted acquaintances — forty-six to one hundred twenty centimeters. The third is social distance — the range people unconsciously hold in everyday professional and social interactions — one hundred twenty to three hundred sixty centimeters. The fourth is public distance — the space between us and strangers, or the gap maintained during speeches, lectures, and performances — anything beyond three hundred sixty centimeters. In his landmark book The Hidden Dimension, Hall argued that just as animals mark territory to defend their space from intruders, humans maintain territorial boundaries calibrated to the nature of each relationship. He coined the term proxemics to describe this idea, and it is now widely applied across sociology and marketing.1
Intimate distance marks your deepest physical and emotional boundary. No matter how close two people are, it should not be crossed casually. This zone is the minimum personal space required to feel safe from external intrusion; when someone enters it uninvited, the body responds with instinctive discomfort or even fear. Allowing someone inside, on the other hand, is an act of identification — it means you have judged them to pose no threat and to harbor no ill intent. Personal distance is roughly the circle your outstretched arms would trace: the border between formality and warmth, the frontier of intimacy. Those who enter this zone are people you feel genuinely close to. Social distance is the space assigned to professional interactions, encoding status and hierarchy. Public distance is the most formal and ceremonial of all.
Shrinking the Distance with Oxytocin
What does neuroscience make of Hall's framework? As we have seen, intimate distance — within forty-six centimeters — is reserved for those closest to us. But people with damage to the amygdala feel no discomfort when a stranger steps as close as thirty-four centimeters. Their amygdala has lost the ability to accurately gauge closeness and threat. In people with a healthy amygdala, by contrast, the structure activates automatically as someone approaches, and real discomfort kicks in the moment the forty-six-centimeter boundary is breached. The amygdala, as we have discussed, functions as the brain's emotional command center. Sitting beside the hippocampus — the seat of short-term memory — it attaches emotional weight to the people we meet and the events we experience. Memories tagged with that emotional significance are then stored in the hippocampus for future recall. Perhaps this is why the amygdala is so closely tied to social behavior. If you know someone with an improbably large circle of friends, or whose relationships seem needlessly complicated, chances are good that their amygdala is bigger than average.2
For romantic partners, spouses, or parents and children, of course, close distance poses no threat at all. Wanting to be nearer to the person you love — to stay in their orbit as long as possible — is the most natural impulse in the world. But in my own experience, when someone of the opposite sex who is not family drifts too close, discomfort arrives immediately. I would simply rather talk from a little farther away. On precisely this subject, a fascinating experiment was conducted at the University of Bonn. Twenty-seven single men and thirty married men took part. In each trial, an attractive young woman walked toward the participant, and the researchers measured how close she could get before the man reported feeling uncomfortable. Half the men had inhaled oxytocin beforehand; the other half, a placebo.
The results were remarkable. Married men who had inhaled oxytocin preferred to keep the woman roughly fifteen centimeters farther away than married men who had taken the placebo. But here is the twist that makes the finding unforgettable: this effect showed up only in married men. The single men? As the woman drew closer, they felt no discomfort at all — only a rising sense of excitement. The researchers concluded that oxytocin plays a pivotal role in helping married couples maintain healthy monogamy. Now the connection between territory and fidelity starts to make sense.3
This study is one of the reasons oxytocin has been called the "morality hormone." Remember the promiscuous montane voles: once scientists restored proper oxytocin-receptor function, those footloose rodents suddenly devoted themselves to a single mate for life and began co-parenting their young. If oxytocin receptors can shape even a rodent's behavior in this way, it is not unreasonable to wonder whether the same molecule might strengthen moral sensibility in humans as well.4 What a remarkable hormone. Some readers may be tempted to slip a dose into their husband's soup. But there is no need for that. Physical affection with your partner, shared meals, and exercising together all raise oxytocin naturally — so find joyful activities that boost it for both of you. Among the best options for couples are ballroom dancing and partner yoga: the ultimate relationship workouts. When you move together, oxytocin rises in both partners at once, deepening love, strengthening mutual care, and — yes — reinforcing faithfulness to each other.
Oxytocin and Married Life
Does the relationship deteriorate because physical affection fades? Or does physical affection fade because the relationship has already started to fray? The answer is both — a feedback loop that can spiral in either direction. Physical touch between spouses activates oxytocin release. As oxytocin rises, couples become more tender, more generous, more inclined to treat each other with warmth. The question, then, is how to set the spiral spinning upward. How do you build an "oxytocin marriage"?
If at all possible, start an activity together that naturally increases physical contact. Ballroom dancing is a perfect example: learning it as a couple multiplies both touch and shared stories, pulling the relationship tighter with each lesson. Hiking, tennis, badminton, golf — any sport done side by side strengthens the bond. Even lower-key pursuits like exploring new restaurants or watching films together boost oxytocin between partners, though not quite as powerfully as physical activity does.
If physical affection has been absent for a long stretch and the air between you has grown awkward, consider an unexpected ally: a dog. Walking together with a pet, making eye contact with it, stroking its fur — all of these raise oxytocin. And finally, one of the most potent tools in the entire oxytocin toolkit: make it a daily habit to find specific reasons to express gratitude to each other. Pair each expression of thanks with a long, genuine hug, and the effect compounds. It will feel stiff at first, maybe even a little silly. Keep going. Before long it will feel natural, your oxytocin will be humming, and you will notice — quietly, unmistakably — that the relationship has begun to heal.