5 Surprising Things You Didn’t Know Were Contagious

Germs aren't the only things you have to worry about "catching." Emotions are also infectious, according to research on social contagions: moods and behaviors that spread from person to person. We like to think we're in control of our well-being, but this research shows that traits and choices of our friends—and even our friends' friends—have a powerful effect on ours. Here are some unexpected infections and our advice on how to inoculate yourself.

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Restaurant Orders

Restaurant OrdersiStock/Thinkstock
Diners are happier when they order entrées that are similar nutritionally to those of their companions, found University of Illinois research. If you’re watching your waistline, place your order first so you’re not tempted by your pals’ cravings.

Negative Thinking

Negative Thinking Image Source/Thinkstock
Freshmen who were randomly paired with roommates highly prone to brooding were likely to “catch” their negative-thinking style after only three months, found a University of Notre Dame study. Recognize that other people may influence how you respond to life’s challenges.


On the other hand, positive feelings also rub off, according to a seminal study of almost 5,000 people by researchers at Harvard and the University of California, San Diego. When you feel happy, a friend who lives within one mile is 25 percent more likely to feel happy, and neighbors are 34 percent more likely to feel happy. The same data found that an extra $5,000 increased happiness by about 2 percent, a much lower impact than what’s gained by having a joyful friend of a friend (a second-degree connection), which can boost your own good feelings by 10 percent.

Quitting Smoking

Quitting Smoking Hemera/Thinkstock
The same research team found that when one person quit smoking, close friends and family members became 36 percent less likely to smoke. The ripple effect: Even very casual acquaintances of the initial quitter became 20 percent less likely to light up.


The brain is hardwired to detect stress in other people, such as increases in breathing rate. This triggers a cascade of our own stress hormones, Heidi Hanna, executive coach and author of Stressaholic, told us. And you don’t need to be in the same room to catch someone else’s stress, which is transmittable via e-mail, texts, and social media. (Curt responses could signal someone is under a tight deadline, for example.) When you feel stressed, take breaks and get enough sleep—that’s not selfish. It benefits everyone around you.

6 Body Quirks You Can "Catch"

6 Body Quirks You Can "Catch" BananaStock/Thinkstock
Yawning, laughing, itching, coughing, vomiting, and crying are all socially contagious. Yawning is so infectious, says psychologist Robert R. Provine, author of Curious Behavior, that we yawn when we see, hear, or even read about someone else doing it. “We are often herd animals, not in full conscious control of our behavior,” adds Provine. Scientists theorize that sharing these quirks conferred an evolutionary advantage: Laughter is a form of bonding; scratching an itch, a safety precaution. (Your brain may think, Hey, their fleas could jump ship and infest me.) Yawning could be how cavemen ancestors synchronized their sleep-wake schedules.

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