A generation’s favorite tune: ‘I’m So Vain’
Young people “love themselves more today than ever before,” says University of Kentucky psychologist Nathan DeWall, and the proof is in their music. He and his colleagues analyzed the lyrics of Billboard Hot 100 songs from the past three decades and found a steady increase in self-centeredness and hostility toward others. “In the early ’80s lyrics, love was easy and positive, and about two people,” study co-author Jean Twenge tells The New York Times. “The recent songs are about what the individual wants, and how she or he has been disappointed or wronged.” The study found a marked increase in the prevalence of the words “I” and “me” in song lyrics, and fewer instances of “we” and “us.” It also registered a jump in angry lyrics about hating and killing, and a drop in songs containing positive words like “love” or “sweet.” The researchers suggest that rampant narcissism may be making it harder for people to connect with one another. They point to other surveys that show that more people are apt to feel sad and lonely now than in previous decades.

Unlocking Mars’ watery past
New radar images have unearthed “a buried treasure” of dry ice beneath Mars’ south pole, NASA scientist Jeffrey Plaut tells the Associated Press. The enormous cache of frozen carbon dioxide, roughly the size of Lake Superior, helps explain why water would periodically be able to collect on the Red Planet’s surface. Every 100,000 years or so, Mars tilts on its axis, allowing more sunlight to reach its south pole and turn that deposit into carbon-dioxide gas. The gas would make the atmosphere more dense, and the greater atmospheric pressure would allow water to pool on the surface as a liquid, rather than exist solely as vapor. A denser atmosphere would also give rise to hurricane-strength dust storms, making the planet “an unpleasant place to hang out,” says lead researcher Roger Philips. Judging from dry riverbeds and deep canyons on Mars’ surface, the planet once had a moist, tropical climate, perhaps billions of years ago. The next challenge for scientists is figuring out how and why the planet eventually lost its surface water.

Fire ants’ cohesive genius
Fire ants aren’t just stinging nuisances, researchers at the Georgia Institute of Technology have found. They are also marvels of engineering teamwork. When a colony is washed out by flood, thousands of the insects quickly assemble into a tightly woven pancake-shaped raft that can float for months without a single ant drowning. “Together they form this really complex material” that water can’t get through, lead researcher Nathan Mlot tells Nature.com. You could even mold the ant cluster “into a ball and toss it up in the air, and all the ants would stay together.” That unique quality comes partly from their superstrength—ants can grip one another with their legs and mandibles with a force 400 times greater than their body weight—but also because the insects are so well organized. By quickly interlocking their thousands of bodies, they create a rough surface that traps air for breathing, makes them more buoyant, and repels water much like the waterproof fabric Gore-Tex does. Bioengineers say the ants offer useful design lessons for everything from better crowd-control schemes to floating robot swarms that clean up oil spills.

Warding off dementia
Just getting out of the house is enough to cut in half your odds of developing Alzheimer’s disease. That’s the heartening conclusion of researchers at the Rush Alzheimer’s Disease Center after they tracked a group of more than 1,000 initially healthy seniors over five years. They found that those who participated in social activities—like lunching with friends, volunteering, or going to church—were 50 percent less likely to develop signs of dementia; the most outgoing seniors reduced their risk by 75 percent. While becoming housebound has long been linked to cognitive decline, scientists hadn’t been sure whether that was just because memory loss makes seniors feel less like going out. Study author Bryan James tells LiveScience.com that his findings suggest it’s the other way around—“that social inactivity itself leads to cognitive impairments.” People who never leave their comfort zone “aren’t engaging with their environment and meeting new people,” he says. “They may not be using their minds as much.” Interacting with others may be a kind of mental exercise that keeps the brain fit. As James puts it, you can either choose to give your mind a regular workout “or lose it.”