by Adam Alter
As you might expect, seasonal effects are strongest in hot climates, where testosterone declines most dramatically in the hot summer months. In one study, researchers examined seasonal birthrates among women across the United States and other countries. In warmer U.S. states—southern states like Louisiana and Georgia—birthrates dipped dramatically in April and May, and rose steeply in August, September, and October. In Louisiana, for example, birthrates were 45 percent higher in the summer months, so that for every two babies born in the winter, three were born in the summer. Of course, counting back nine months, these results suggest that many more babies are conceived in the winter than in the summer. Researchers haven’t agreed on why conception rates rise in winter, though they’ve identified several possibilities: people spend more time indoors; men are more likely to seek romance because their testosterone levels rise in winter; men are more attracted to the female figure as they’re exposed to it less often when the weather cools. There’s also one final, fascinating explanation that began with a cloth-covered monkey fifty years ago, and ends with a cup of hot coffee today.
The Literal Chill of Social Isolation
In the late 1950s, psychologist Harry Harlow conducted one of the most famous psychological studies of all time. Two decades earlier, Harlow was studying intelligence in baby rhesus monkeys when he became fixated on something far more interesting. Each time he separated the baby monkeys from their mothers, they would cling to the terry-cloth towels lining the floors of their cages. When he tried to remove the cloth from their cages, the monkeys threw violent tantrums, screeching and pounding the floor of the cage until he returned the fabric. He began to wonder whether the monkeys, lonely without their mothers, found some small consolation in the warmth of their tatty towels.
Harlow’s observation was a revelation. In the 1950s, most psychologists assumed that baby animals “loved” their mothers because they needed food and water. In fact, the word “love” was anathema because it implied some deeper mental experience that was too woolly for scientific study. They decided instead that baby animals were demonstrating “proximity”—a survival instinct that drove them to latch on to their mothers. But Harlow could see that these young, traumatized monkeys were seeking more than milk. They were looking for warmth and affection.
Harlow’s research interests took a dramatic turn. He stopped focusing on animal intelligence and turned his mind to the question of why baby monkeys, like human infants, cling to their mothers for support. Was it because their mothers fed them and kept them alive, just as wild animals try not to stray too far from an isolated lake in the dry season? Or was it because their mothers provided comfort and warmth, particularly when the young monkeys were scared or anxious? Harlow knew that mothers fulfilled both needs—biological and social—but he wondered which one was most directly responsible for mother-infant bonding. To answer his question, he removed newborn monkeys from their mothers and placed each one in a cage with two artificial “mothers.” One mother was constructed of an unyielding wire frame, but the researchers attached a bottle to the frame so the infant monkeys were forced to return to her whenever they wanted milk. The other “mother” was covered in soft fabric, but she had no milk. Harlow watched as the traumatized young monkeys met their new mothers for the first time. Almost immediately they clung to their cloth mothers, avoiding the severe wire mother except when they reluctantly approached her for milk. Harlow’s monkeys were far more attracted to the cloth mothers’ physical warmth than they were to the wire mothers’ promise of nourishment. Baby monkeys aren’t supposed to be separated from their mothers, and the warmth they experienced when clinging to their cloth mothers was a stand-in for the genuine motherly comfort they should have been receiving from their real mothers.
Fifty years later, social psychologists took Harlow’s findings one step further when they began to wonder whether physical warmth actually compensates for the pain of social isolation. In one experiment, students met an experimenter in the university’s psychology department lobby. Together they rode in an elevator to the experimental lab on the building’s fourth floor. During the ride, the experimenter asked the student to hold her cup of coffee just briefly, so she could quickly write down the student’s name and experiment time. Half of the students held a cup of hot coffee, while the other half held a cup of iced coffee instead. About fifteen seconds later, when the elevator reached the fourth floor, they continued to the psychology lab, and the student completed a brief questionnaire. The questionnaire described an anonymous “Person A” as intelligent, skillful, industrious, determined, practical, and cautious, and the students were asked to rate Person A’s personality on a range of scales. For example, did he seem generous or ungenerous, caring or selfish, attractive or unattractive, strong or weak? When the researchers looked at the results, they found that the students rated Person A as significantly warmer and friendlier (but not more attractive or strong) when they had earlier held the cup of hot coffee rather than the cup of iced coffee. The students confused the physical sensation of cradling a warm cup of coffee for the metaphorical sense that Person A was warm and friendly.
In other experiments, students held a therapeutic pack that was either heated in a microwave or cooled in a freezer. Those who held the pack when it was cold reported feeling lonelier, claiming that they were starved for company and had no one to talk to more often than did the students who held the heated pack. Other students who were asked to remember a time when they felt lonely or socially excluded were later more interested in spending time with close friends—unless they held a heated therapeutic pack in the interim. The sensation of physical warmth alleviated the need for social contact, suggesting that the brain interprets physical and social warmth very similarly. One brain region that responds to both cool temperatures and social isolation is known as the insula, a small region buried in a fold of the mammalian brain’s outer layer. The insula processes all sorts of visceral information, from pain to temperature changes, while also responding to the experience of trusting other people when forming social connections. Some researchers believe that physical coldness activates the insula, which leads people to feel lonely and socially isolated, and to seek social comfort in an attempt to overcome this sense of loneliness.
There’s a lesson for film studios buried in this research, which comes down to a question of timing. Building on the relationship between cold and loneliness, two marketing researchers turned their attention to romantic comedies, the cinematic equivalent of Harlow’s cloth mother and a cup of warm coffee. The best romantic comedies place their central character in a cold, affectionless wasteland, before redeeming him (or, increasingly often, her) with a warm, newfound love interest. Since romantic comedies are designed to warm a frigid heart, in two experiments people who were handed a cup of iced coffee, or a cold therapeutic pack (rather than a cup of hot coffee or a heated therapeutic pack) were willing to pay an average of 20 percent more to see a romantic comedy film. They weren’t willing to pay more for action films, comedies, or thrillers, presumably because those films lacked the heartwarming promise of romantic comedies. The experimenters concluded by looking at the film rental patterns of 2,500 U.S. residents, focusing on the relationship between daily temperatures and genre preferences. Even when they excluded Valentine’s Day—a cold mid-February day that heralds a spike in romantic comedy rentals—they found that when the weather was colder, people rented more romantic comedies than films of other genres.
Bad weather brings us together, but protracted rain, snow, and darkness are also responsible for great unhappiness. As he led a group of sailors through dense Arctic ice floes in the late nineteenth century, U.S. explorer Frederick Cook noticed that his men were becoming more and more lethargic. Cook was confused, because he’d never seen a crew descend so quickly into a collective malaise, and he also realized that every last man would perish unless he intervened.
Weather and Well-Being
As Cook�
��s ship labored through the roiling, icy sea, he began to wonder whether he and the sailors would die in the darkness. After considering a range of far-fetched causes and remedies that were completely ineffective, Cook realized that the men were suffering from an acute lack of sunlight, so he devised several ingenious treatments. His “light cure” required that affected men sit in front of an open fire for several hours each day, bathing in its heat and glow. After each treatment, the men were briefly reinvigorated, returning to their former summery selves. Cook’s cure was remarkably prescient, coming a century before blue SAD lamps were invented. Meanwhile, other men were forced to march in circles on the ship’s small, icy deck, an area that the men dubbed “the madman’s promenade.” Exercise, like natural light, undid the ravages of the prolonged Arctic darkness. Later, Cook observed a group of Inuit people who had adapted to the dark winter over generations. Mimicking the behavior of hibernating animals, the Inuit hunkered down during the winter and welcomed the chance to enjoy prolonged sleep and extended sessions of small talk and gossip. When the sun finally rose, they were seized by a springtime euphoria that included dancing and courting.
Scientists now recognize that SAD is tied to the ebbs and flows of our circadian rhythm—the internal body clock that regulates when we sleep and stir. As I mentioned earlier, in chapter 7, when this internal clock is disrupted—for example, when we traverse time zones and experience jet lag—our bodies and brains struggle to complete even basic mental and biological tasks. In humans, the hormone melatonin is largely responsible for driving the circadian cycle. Melatonin, secreted by the pineal gland, is absent during daylight and begins to flood the body before bedtime. As the days shorten in winter, sufferers of SAD are forced to fight against a soporific tide of melatonin for longer periods, struggling to accomplish during the shortened day what they would otherwise accomplish more easily during the longer days of summer. As we saw earlier, physicians often treat wintertime SAD with blue light that mimics the wavelengths of natural sunshine. These SAD lights are effective because they emit up to 10,000 lux of light, far more than the 300 lux that it takes to halt melatonin production, or the 700 lux emitted by the rising sun.
Across the ages, these summer highs and winter lows have been especially pronounced among artists, writers, and intellectuals. Vincent Van Gogh swung wildly between his famous periods of wintertime melancholy and extreme periods of summertime elation. On the shortest, darkest, coldest night of the year in December 1888, Van Gogh fought viciously with his erstwhile friend and fellow painter Paul Gauguin, first throwing a glass of absinthe at Gauguin’s head and then chasing him down a dark street with a straight razor. Later that night, Van Gogh used the same razor to sever his right earlobe, which he supposedly mailed to a prostitute named Rachel. Van Gogh’s artworks were similarly swayed by the seasons, dominated by ominous clouds and darkness in the winter months, and optimistic sunshine, light, and stars during the summer months. His aggressive brushstrokes, loaded with mounds of paint, became more frenzied in the winter months and lost some of their intensity when summer arrived. Van Gogh wasn’t alone; German polymath Johann Wolfgang von Goethe complained that “excellent personalities“—including his own—“suffer most from the adverse effects of the atmosphere.” Composers Handel and Mahler also succumbed to the seasons, producing many of their great works in the fall and spring, when they weren’t at the mercy of debilitating wintertime lows and manic summertime highs.
Like SAD, many of the weather’s strongest effects are based in animal biology. Although weather events affect humans, certain lower-order animals are more attuned to changes in the weather, so they respond more quickly and dramatically than do humans. In the particularly active Atlantic hurricane season of 2004, scientists tracked the movement of sharks in the bays along Florida’s west coast. Long before the wind and rain from Hurricane Charley chased Floridians from the coast in August 2004, the sharks fled en masse to the deeper, safer waters of the Gulf of Mexico. Scientists were baffled, until they discovered that the sharks had responded to rapid drops in barometric pressure—early warning signs of an impending storm. Other researchers have found similar behavior among dogs, bees, birds, and elephants, which seek shelter and higher ground when air pressure falls before hurricanes, tropical storms, and even earthquakes and tsunamis. Humans aren’t quite as shrewd, but studies have shown that people exhibit a wide range of surprisingly disordered responses when the weather changes.
As storms and high winds roll into a region, they introduce electrically charged particles, or ions, into the atmosphere. For decades throughout the twentieth century, observers claimed that the onset of strong winds—like the Santa Ana in California, the chinook in the Pacific Northwest, the sirocco in Italy, and the sharav in Israel—brought strange changes in human behavior. In Red Wind, his classic 1938 hard-boiled detective story, Raymond Chandler mentions the malevolent Santa Ana twenty-six times. The wind becomes a bona fide character, responsible for boozy parties that end in fights, and wives who contemplate slitting their husbands’ throats with carving knives.
Residents of Alpine Europe commonly associate the local foehn winds with a range of maladies from migraines to psychosis, and aspirin bottles in Germany sometimes advertise the medication’s ability to treat Foehnkrankheit, or foehn sickness. Foehn winds roll down mountainsides, warming the weather by up to 50°F (28°C) in a matter of hours, and they’re largely responsible for central Europe’s relatively mild temperatures. Adolf Hitler’s friend Heinrich Hoffman claimed that a foehn wind was responsible for Hitler’s headache when the two went election campaigning on the evening of September 18, 1931—the same night that Hitler’s niece Geli Raubal was found dead with a self-inflicted gunshot wound to the chest.
In the early 1960s, German researchers investigated the relationship between the foehn winds in Alpine Europe and accident and injury rates in German factories. They divided the weather into six phases, three of them relatively calm and three associated with disturbances from foehn winds, storms, and post-storm recovery. During the three disturbed foehn phases, people were slower to react to visual cues at a traffic exhibition in Munich, accident rates at a heavy machinery plant were especially high, and workers at a second industrial plant were more likely to report to the plant’s doctor’s office for medical attention. After observing the behavior of almost thirty thousand German exhibition visitors and industrial workers, the researchers concluded that foehn sickness was a real phenomenon, and that atmospheric changes were responsible for symptoms as varied as slowed reaction times and physical illness.
Twenty years later, two American researchers were puzzled by exactly why seasonal winds affect people so dramatically. Obviously something in the winds was causing headaches and other sickness, but the epidemiological data that established the link left many questions unanswered. Since winds and storms change the electrical composition of the atmosphere, the researchers decided to investigate how people in closed lab rooms responded when electrically charged ions were carefully released into the air. They expected these positive ions to interfere with participants’ central nervous system functioning, increasing production of a neurotransmitter known as serotonin 5-HT, which contributes to hyperactivity and aggression. Nearly a hundred people responded to advertisements, each spending ninety minutes in a sealed room fitted with three ion generators. Each person sat in the room twice, once with the generators switched on, mimicking the atmospheric effects of an oncoming windstorm by slowly increasing the concentration of positive ions in the air, and once with the generators switched off—a control condition that was identical to the storm condition, except that the room wasn’t filled with positive ions. Throughout each ninety-minute period, the participants completed a series of scales and tasks designed to measure their emotional and mental functioning. When the researchers analyzed the results, they found that the positive ions made the participants more tense and tired, and less sociable and happy. According to the researchers
, this constellation of damaging responses explained why winds and weather changes are associated with suicide, depression, irritability, crime, and industrial and automobile accidents.
But it isn’t just unsettled weather that blunts the mind, as researchers have begun to discover more recently. Every year Mercer, a global human resources company, rates the quality of life in major cities around the world. The ratings combine thirty-nine different measures, from crime to restaurant quality to political stability. Chief among those measures is climate, which elevates sunnier cities with mild temperatures, and hampers cities with long, cold winters and plenty of rain. Paradoxically, though Mercer rates mild, sunny cities more favorably than wintry, rainy cities, one group of researchers has cast a metaphorical cloud over sunny cities.
Sunshine Dulls the Mind to Risk and Thoughtfulness
The same mental haze that sets in after weeks on a summer vacation also muddles the mind from one sunny day to the next. This might seem like an outrageous claim—that sunnier days bring on a mental stupor—but it’s a claim that’s backed with real-world evidence. In one study, social psychologists sprang a surprise memory test on shoppers who were leaving a small magazine shop in Sydney, Australia. Before the shoppers entered the store, the researchers placed ten small ornamental objects on the store counter—four plastic animals, a toy cannon, a piggy bank, and four Matchbox cars. After leaving the store, the shoppers were asked to remember as many of the ten items as possible, and to also pick the ten items from a list of twenty that included the ten correct items and ten new items. The researchers conducted the experiment on fourteen different days across a two-month period, between 11:00 a.m. and 4:00 p.m.; some of those days were clear and sunny, whereas others were cloudy and rainy. The shoppers recalled three times as many items on the rainy days as on the sunny days, and they were approximately four times as accurate when identifying the ten objects from the longer list of twenty items.