Advertisement - Continue Reading Below

You know that colds, the flu and even yawning are contagious, but you probably don't know some unexpected emotions and behaviors — some good and some not-so-good — also can catch on. Researchers believe these encourage people to cooperate with each other and understand what can help them and hurt them so they stay healthy and out of harm's way. But we often share this info without realizing it through body language, facial expressions, and even scent. Here are 10 surprising things you just might pass on to people around you.

More From Good Housekeeping

1. Stress
Talk about sharing the load: Research from the March 2012 issue of Social Neurosciencefound that merely seeing an anxious person can up your own cortisol, a stress hormone. In other research from Social Cognitive & Affective Neuroscience, people became more alert when exposed to the undetectable odor of sweat from a stressed-out person. These cues may prepare us for potential danger, says Lilianne R. Mujica-Parodi, PhD, associate professor of biomedical engineering at Stony Brook University School of Medicine in Stony Brook, NY.

2. Goals
Have you ever marveled at how a kid couldn'tcare less about a toy until another totreaches for it? There's a reason for that: In a 2012 study, participants rated an object as more desirable when they thought someone else's goal was to own it. Wanting what others have may help us learn "what's good for you without having to try everything yourself, which would be riskier and more time consuming," says Mathias Pessiglione, PhD, clinical psychologist and research team leader at the Brain and Spine Institute at Pitié-Salpêtrière Hospital in Paris, France.

RELATED: A 24-Hour Guide to Boosting Your Immunity

3. Joy
It turns out it isn't even necessary to have direct contact with someone (or their pheromones!) for their feelings to rub off on you. A study published in 2013 with the Public Library of Science's publication, PLoS ONE, found that people can catch another person's happiness by watching someone else watching the joyful person. "Our emotions can quickly and subtly be transmitted to others, even if it's unintentional," says Guillaume Dezecache, PhD, a postdoctoral researcher at the University of St. Andrews in Fife, Scotland. And they can make a big impact. For example, just one employee's cheerful attitude can spread cooperation and reduce conflict in the workplace.

4. Fear
You know how dread can spread rapidly through a crowd for no apparent reason? Now researchers have a clue as to why it might occur:When participants in one study smelled the sweat of a frightened person, they made fearful facial expressions and were more alert, suggesting that they caught the other person's fear. Researchers believe this response may help people survive by communicating info about looming threats.

5. Disgust
Pheromones, chemical signals people unknowingly release, can also communicate disgust, according to the same study that examined fear. Participants were more likely to make repulsed expressions and sniff less often when they smelled disgusted people's sweat. Researchers say this response may minimize exposure to foul-smelling, potentially toxic chemicals in the air.

6. Loneliness
Sounds counterintuitive, but you can catch feeling isolated, according to a recent study. "Loneliness makes people more negative, irritable and defensive," which can protect you if you're in an unsafe setting, says John T. Cacioppo, PhD, professor and director of the Center for Cognitive and Social Neuroscience at the University of Chicago in Illinois. Lonely folks are more likely to treat others badly; those people then do the same to others, and the cycle continues. Be aware of these effects, and when you're with a trusted friend, rein in behavior that might alienate people.

RELATED: 9 Things You Need to Stop Stressing About

7. Negative thought patterns
It's not only moods and emotions that can be transmitted but also ways of thinking, like the tendency to perceive situations as worse than they are. Recent research has found that new college students often adopt their roommate's thinking style, for better or worse. "Those assigned to a more positive roommate developed a more positive thinking style themselves," and likewise with the negative roommates, says study co-author Gerald Haeffel, PhD, associate professor at the University of Notre Dame near South Bend, IN. This might be due to modeling, inadvertently imitating someone else's behavior. Keep in mind that your outlook can be swayed by the people you're close to, and since your mentality can affect them, too, take steps to shift it if you're the Debbie Downer in the group.

8. Breathlessness
Look away when you spot a guy at the gym with inflated cheeks and a red face! Watching someone hold their breath can make you feel out of breath yourself and can actually quicken your breathing, suggests a 2012 study in Respiratory Physiology & Neurobiology. Researchers link this with our capacity for empathy, since physical sensations are a part of the way we experience emotions. It's not that we feel empathy toward the person; we just can't help but have an involuntary response similar to what they're experiencing.

9. Itchiness
This will have you scratching your head — or some other part of your body. Watching someone scratch makes people feel itchy and more likely to scratch themselves in response, reports a 2012 study in the Proceedings of the National Academy of Sciences of the United States of America. Seeing someone scratching herself activates the same areas of the brain involved in the physical perception of itchiness, probably because of our empathetic tendencies. So if you don't want others to think you have a rash, avert your gaze when someone's scratching away.

This story originally appeared on

What do you think?