Health & Science

Twitter reveals humanity’s mood swings

People everywhere tend to feel chipper at breakfast, get grumpier over the course of the day, and brighten again before going to bed. That is the central finding of a vast new study of Twitter users, which may be even more significant in establishing social-networking sites as “the foundation of a new social science,” Harvard University sociologist Nicholas A. Christakis tells The Washington Post. Researchers at Cornell University tracked the changing moods of 2.4 million people in 84 countries over two years by analyzing their tweets. Using special software, they searched some half a billion posts for words that indicated positive feelings, like “awesome” and “fantastic,” or negative feelings, such as “panic” and “fear.” When they graphed the results based on the timing of the posts, they discovered a universal daily pattern: Happiness peaks around breakfast, between 6 a.m. and 9 a.m.; falls to a low between 3 p.m. and 4 p.m.; and then rises to another high after dinner. The same trend holds true on weekends, when most people aren’t at work. The study, the first to track the emotions of so many people across cultures, suggests that innate biological rhythms play a big role in our moods.

A new view of oddball Mercury

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NASA’s Messenger probe, the first ever to orbit Mercury, has already shattered existing theories about how the planet formed. Because Mercury has an unusually large iron core, scientists previously believed that the planet closest to the sun began as a much bigger orb, and that its outer layers had either been burned off by fiery asteroid collisions or boiled away by heat from the sun. But Messenger’s close-range scan of the planet’s surface has revealed high levels of sulfur and other elements called volatiles, which would have vaporized long ago under either of those scenarios. Their presence essentially rules out existing “theories for the planet’s formation,” Patrick Peplowski of Johns Hopkins University tells BBCNews.com. The probe also returned close-up photos of strange, bright blue “hollows” pocking Mercury’s surface, ranging from dozens of feet to several miles wide, and new evidence that volcanic activity billions of years ago sent enormous quantities of lava to the planet’s outer layers. “Messenger is really revealing a planet that is completely an oddball in every characteristic we can measure,” says study co-author David Blewett, causing scientists to rethink their view of it as “an old burned-out cinder.”

Can birth control spread HIV?

Hormone shots widely used in Africa to prevent pregnancy may make women more likely to contract HIV—and to pass the disease on to their partners. Researchers studied 3,790 African couples in which one partner already had the virus. They found that women who used hormonal birth control were twice as likely as those who didn’t to get HIV from their partners or to infect them with the disease. If “these contraceptions are helping spread the AIDS epidemic, we have a major health crisis on our hands,” Isobel Coleman, a policy director at the Council on Foreign Relations, tells The New York Times. Especially in eastern and southern Africa, where birth rates are among the highest in the world, hormone shots are a vital tool for preventing unintended pregnancies, which often come with life-threatening complications. Researchers still aren’t sure how the use of hormonal contraceptives leads to the spread of HIV; some experts say the shots may discourage the use of condoms, though the study supposedly accounts for any variation in condom use. It’s possible, researchers suggested, that the hormone shots thin vaginal tissue, making it easier for the virus to pass through. In sub-Saharan Africa, some 12 million women depend on hormonal birth control and 16 million have HIV.

Why some teams seem cursed

Sports teams with a history of choking under pressure are more likely to choke again, says a new study. The study, by the Norwegian School of Sport Sciences, found that a team’s previous failures—even if they happened years earlier—make current players more self-conscious and more likely to perform badly under pressure, reports Miller-McCune. Researchers analyzed 30 years’ worth of championship soccer penalty-kick shoot-outs, the high-pressure encounters used to decide tied games. They found that kickers on teams that had lost their last shoot-out were 20 percent less likely to score than those on teams that had won theirs—even if those earlier games took place long before the current players made the roster. The caliber of the players themselves—and their teams’ recent success—didn’t seem to change their odds of succeeding in the clutch. Playing for a team with a history of losing big games, the study authors theorize, infects athletes with crippling “performance pressure.” Playing for a winning team, on the other hand, provides “lower levels of emotional distress, making players slow down their preparation and focus more on the shot.”