The Village Effect: How Face-to-Face Contact Can Make Us Healthier and Happier (13 page)

Meanwhile, the footfalls of people crossing a bridge at the same time can become so coordinated as to collapse the structure. This almost happened on June 10, 2000, when London’s elegant Millennium Bridge started swinging precariously as soon
as it was opened to the public. Designed to allow London pedestrians to traverse the Thames between the Tate Modern and St. Paul’s Cathedral, the bridge’s arcing steel balustrades, resembling a giant spider’s filaments, are the epitome of sturdy modern design. The supports are not only graceful, they don’t sag as much as other suspension bridges. Yet, as journalist John Cassidy reported in the
New Yorker
,

The reason for the wobble, the engineers discovered, was that too many people had “caught” the rhythm of their neighbors’ gait. When everyone was moving in lockstep, the bridge started to move in synchrony. “Once the footway starts swaying, however subtly, more and more pedestrians adjust their gait to get comfortable, stepping to and fro in synch. As a positive-feedback loop develops between the bridge’s swing and the pedestrian’s stride, the sideways forces can increase dramatically and the bridge can lurch violently,” Cassidy wrote. The same goes for the financial markets, he added, referring to the work of the Princeton economist Hyun Song Shin. “Where previously there were diverse views, now there is unanimity: everybody’s moving in lockstep.”
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Whether it’s birds flying, whales singing, chimps banging, or bridges swaying, there is an infectious aspect to each individual’s behavior that makes the whole more than the sum of its parts.

INVISIBLE SIGNALS

Close physical proximity is crucial to emotional contagion. Good fiction writers know this, making observations about one character’s loopy stride, or the ammoniac scent of dread of another’s plaid shirt that pull the unsuspecting reader right into a scene. In
Annie John
, Jamaica Kincaid’s coming-of-age novel set on the island of Antigua, her young protagonist’s tight synchrony with her newfound best friend tells us all we need to know about an adolescent’s heady first experiments in intimacy. Like teenagers everywhere, the two girls do the same thing at the same time in the same way, yet attribute their matchiness to karma:

Kincaid might have added the uterus while she was at it. In the late 1960s, when the American experimental psychologist, Martha McClintock, was an undergraduate at an all-girls college in suburban Massachusetts, she noticed that as she and her Wellesley roommates began to spend more and more time together, their menstrual periods became synchronized. When she mentioned it to several male scientists who were discussing a similar phenomenon in caged female mice, her frank observation prompted ridicule. “Don’t you know? Women do that, too,” she remembers telling the skeptics at a summer workshop at the Jackson Labs in Maine. Three years later, in 1971, twenty-three-year-old McClintock showed them. In a pioneering article published in
Nature
, titled “Menstrual Synchrony and Suppression,” McClintock showed how increased social interaction among 135 female roommates and close friends prompted their
menstrual cycles to overlap. The synchrony of the young women’s periods hinged not only on time spent together but on the intimacy of the relationship—close friends had greater synchrony than roommates who were just roommates. McClintock hypothesized that the catalyst was pheromones: airborne microscopic, odorless chemical signals about our emotional states that can shift the behavior of people who are close to us.

Today menstrual synchrony is called the McClintock Effect, and it has been found in women living in college dormitories (single-sex and co-ed), on kibbutzim, in cohabiting mothers and daughters, in lesbian couples, in commune and co-op residents, and among nurses and female office workers.
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Menstrual synchrony is not universal, and scientists are still debating how it works. Still, even if the mechanisms underlying face-to-face contagion remain obscure, the McClintock Effect tells us that details about our emotional or reproductive status can be communicated to others—without our permission, and without their awareness.

If you’re wondering why anyone would care about this phenomenon, consider this bizarre research finding. Geoffrey Miller, an evolutionary psychologist at the University of New Mexico, managed to persuade eighteen lap dancers in Albuquerque to participate in a study designed to track their earnings against their menstrual cycles. This wasn’t a huge sample but the dancers worked long hours, so Miller and his two colleagues were able to map 5,300 lap dances over two months’ time. The experimenters had never met the performers, who were given ID numbers to preserve their anonymity and a confidential mailbox where they could drop off their completed questionnaires. When the researchers mapped where a dancer was in her cycle against her earnings per five-hour shift, they discovered an intriguing pattern. The male patrons unwittingly selected ovulating women more often than they chose women who were menstruating. The ovulating women also seemed to be earning bigger tips per dance. In the fertile
phase of their cycles, the dancers earned $354 per five-hour shift, or $70 per hour. Menstruating women earned $185 per shift, or $35 per hour, exactly half that amount. (Meanwhile, between the two phases of their cycles, the women earned $264.)
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Where our primate relatives advertise their fertility with colorful genital swellings, human primates have evolved to be somewhat more subtle. But we communicate this information nonetheless, with invisible signals that can have a transformative effect on our friends, not to mention our pocketbooks. Powerful women such as IMF head Christine Lagarde, Hillary Clinton, and Michelle Obama understand the importance of their appearance when meeting people face-to-face. And it’s not just women who benefit from appearances. Research shows that, on average, tall men earn more than their shorter colleagues, and women on the lookout for male companions prefer those who are expensively dressed.
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Like it or not, we broadcast a range of signals—such as hormonal fluctuations, behavioral synchrony, and other “in-person” indicators—that require us to be in the same room with another person for the message to hit home. And the stakes can be high, altering not only the contents of our pocketbooks but also our plans for the future.

PREGNANCY IS CATCHY

When a young Montreal couple, whom I’ll call Diane and Bob, considered starting a family, they told me they didn’t think it was anyone’s business but their own. Like any young couple, they were a world unto themselves, wrapped up in each other, everyone else on the outside. Or so they thought. But when Bob heard that his older sister’s first baby had just been born, he dropped everything and bought a plane ticket. He wanted to meet this baby.

At thirty-one, Bob was five years younger than his sister. His wife, Diane, had only recently graduated from university, and while they had been thinking about having kids, they were wondering whether it was really the right time. “There were some things
I wanted to make sure we had in life before we had our first kid. I’d been saying to Diane, ‘Let’s wait, let’s think about it,’ ” Bob told me as we drank tea in his sunny kitchen in the Mile End neighborhood of Montreal.

The day his niece was born, Bob held her against his chest, and she fell asleep there for over an hour. “That was so nice,” he recalled, eyes focused on the middle distance. “I remember that as soon as the baby woke up I called Diane, saying—”

At this point the more reserved Diane jumped in to finish his sentence, “—‘I want one!’ ” Six months later, Diane was pregnant with their first child, now a lively, curly-haired little girl named Jessica.

This conversation would be no more than a sentimental anecdote if it didn’t illustrate a surprising finding. Fertility is contagious between siblings, according to research by Columbia University economist Ilyana Kuziemko. And the contagion isn’t between just any two siblings—it starts with a sister’s pregnancy. It’s as if she transmits her fertility to her siblings, especially after her first child is born. At that point the likelihood that one of her brothers or sisters will decide to start a family within the next two years jumps by 30 percent. And the contagion goes in only one direction. “The most striking finding is that fertility rises dramatically for both men and women after their
sister
has a child—yet the birth of a child to a brother appears to have no effect on an individual’s fertility,” Kuziemko writes.
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How do siblings “catch” pregnancy from each other? Kuziemko suggests that the prospect of having a baby becomes more appealing after a sister has one. She’s suddenly in a position to pass on timely childcare and medical information, not to mention hand-me-downs and the skinny on the best preschools. This makes sense, given that the contagion effect is strongest for siblings who live near each other. There are also other incentives to ensure that an extended family’s babies are clustered by age. Social scientists call these subtle influences “network externalities,” which is just a
fancy way of saying that the fun and benefit of doing things together outweighs doing them alone.

Could something other than social contagion be at the root of the sibling baby boomlet that follows a sister’s first child? Siblings who are two years apart in age might naturally space their children the same way, for instance, so that the pattern mimics the domino effect. Or perhaps sibs explicitly plan to have children in close succession, thus creating a little soccer team for their extended families. When I raised these possibilities, Kuziemko said no, having babies really is contagious. “The sibling effects are
in addition
to any coincidental correlations in the fertility patterns of individual siblings,” she told me. Adult siblings are significantly more likely to have a baby, increasing their family size, as a reaction to their sister having a baby. The effect isn’t immediate. Most childless siblings take time to absorb the information, often only deciding to have a baby themselves after connecting with a niece or nephew face-to-face—or chest-to-chest—then thinking it over for a few months. By that time, many of them want one for themselves.

WHETHER YOU WANT ONE OR NOT

Among teenagers, pregnancy can be particularly contagious. In September 2008, in the middle of the election campaign, US vice-presidential candidate Sarah Palin’s seventeen-year-old daughter Bristol announced that she was pregnant. Far from outrage, the ensuing avalanche of support from evangelical Christians revealed that many of them didn’t seem to find a pregnant high-school student all that unusual. Like tattoos, once emblems of biker gangs and prison culture, teenage pregnancy had become so common in the community as to become respectable. Keeping the baby was regarded as a sign of moral fiber. “Like so many other American families who are in the same situation, I think it’s great that she instilled in her daughter the values to have the child and not sneak off someplace and have an abortion,” a Louisiana delegate told a
reporter at the Republican convention. Writing in the
New Yorker
later that fall, Margaret Talbot quoted Marlys Popma, head of evangelical outreach for John McCain’s campaign, expressing a similar sentiment. “There hasn’t been one evangelical family that hasn’t gone through some sort of situation,” said Ms. Popma.
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Even Bristol Palin added her two cents: “Everyone should be abstinent, but it’s not realistic at all.… Sex is just more and more accepted now among kids my age.”

While 75 percent of evangelical teenagers say they believe that there should be no sex before marriage (compared to 50 percent of other Protestants and 25 percent of Jews), their convictions and their behavior collide. According to a huge US government survey of adolescents, even though three-quarters of them oppose premarital sex, teens from evangelical and conservative Christian families have an earlier sexual debut, are more sexually active, and are less likely to use contraception than teenagers from nearly every other religious group in America.
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This disconnect has subtle social roots. As Mark Regnerus, a sociologist at the University of Texas, points out in his book on teenage sex and religion,
Forbidden Fruit
, abstinence pledgers—a trend among evangelical Protestant teens—are unlikely to use contraception the first few times they have sex. “More often than not they will have experienced first sex without planning to do so, and lack of planning usually means lack of contraception. For such youth to introduce contraception into their own sexual activity would require a drastic change of script,” he writes. As virginity is a big deal and they’re not supposed to be thinking about sex before marriage, “sex eventually ‘happens’ to most evangelical youths, despite their best intentions.” That’s one reason why their STD infection and pregnancy rates trump those of other American teens.
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The no-sex-before-marriage rule, combined with an aversion to talking about sex, contraception, and abortion, creates a knowledge vacuum. Then, as more and more
teens become pregnant, what was initially taboo gradually becomes acceptable, if not contagious, within the group—even if its members don’t want it to.