How our social circles shape our choices

Most of us are aware of how our family members and close friends can impact certain choices we make, such as where we live and what professions we enter. But new, scientific studies reveal that social influence is far more powerful and widespread than we realize and doesn’t end with just the people we know well.

Behavior and emotions are extremely contagious. They spread from person to person like germs, touching thousands of people, influencing everything from our happiness and professional success to whether we gain weight or even get divorced. It sounds odd because as human beings, we like to believe that we — not our families or our social networks — are in control of personal and private decisions. But the truth is, we’re often deeply influenced by events we do not witness that happen to people we do not even know.

These findings are helping to explain why so many individuals are obese and why millions of people bought houses they couldn’t afford, a factor leading to the recession. Understanding these findings can help us counteract the negative effects of social influence, as well as foster its positive effects.

To explain this phenomenon and harness its power, Bottom Line/Personal spoke with Harvard professor Nicholas A. Christakis, MD, PhD, whose groundbreaking work led Time magazine last year to name him one of the 100 most influential people in the world.

What mass behaviors are rippling through society right now? The first things I researched — in collaboration with my colleague, political scientist James Fowler, PhD — were overeating and obesity, which have become a puzzling epidemic in this country. Nine states in the country now report that more than 30% of their residents are obese. Why is our nation so fat when there is so much agreement and awareness about the dangers of being overweight?

I used a study that tracked the intimate details and behaviors of a community of thousands of people in Framingham, Massachusetts, over more than 30 years. This data let us track people’s connections, the sequences of their ties and how they interacted. What we found was stunning. When we charted the spread of obesity through Framingham, it followed a pattern very similar to the way an infectious disease such as the flu spreads. If your family members or friends were obese, your risk of becoming obese was 45% higher. If a friend of your friend was obese — even if you didn’t know him/her — your chances were 25% higher. What this suggested was that a key factor in determining health wasn’t just your own willpower or exercise regime, but also the health of your extended social network.

How far out does this ripple effect extend? We went on to study a diverse set of “contagions” moving through human networks — everything from back pain and suicide to sexual practices and drinking. In most cases, the spread of a social contagion obeyed what we called “Three Degrees of Influence.” Our actions and choices affected our friends (one degree), our friends’ friends (two degrees) and even our friends’ friends’ friends (three degrees) before the influence grew weak and dissipated. Likewise, we ourselves are influenced by people within three degrees but generally not more.

The typical person’s inner circle of close family and friends ranges from two to 12 people, and each of their outer circle of coworkers, neighbors and occasional friends is about 150, so we are each connected to and affected by thousands of other people. We spend our lives embedded in these living, breathing social webs.

How does this ripple effect contribute to divorce? Divorce seems like one of the most personal and individual choices you could make, but it, too, can spread among people. We found that if your friend gets divorced, it increases the likelihood that you’ll get divorced by about 147%. A person with a divorced sibling was 22% more likely to get a divorce even if he/she wasn’t close to the sibling.

How do social contagions actually spread from person to person? Through a variety of mechanisms, such as direct imitative behavior, similar environmental exposures and our propensity to gather around us people who think and act like us. At the same time, they also can spread in a more subtle way — through our desire to fit in and conform to social norms. Friends and family members change your notion of what’s acceptable or desirable, which in turn can influence your behavior and feelings.

For example, let’s say that you have friends who are obese. Simply socializing with those friends can alter your idea of an acceptable body size and make you more susceptible. You might feel you look so good in comparison to your heavy friends that it’s not such a big deal if you gain an extra few pounds. So you let yourself have an extra dessert that night, and you don’t get up early to go to the gym the next day.

Do all behavior and emotions spread the same way? No, and that’s the fascinating part. Like different germs, different contagious behaviors spread in their own unique ways.

For emotional states such as happiness, loneliness and depression, physical proximity is very important. A person is 15% more likely to feel happy if his friend (one degree away) is happy. But that’s only true if the friend lives within one mile of him. Further away, and the effect dissipates. On the other hand, when it comes to behaviors such as obesity and smoking, your friends who live hundreds of miles away have just as big an impact on you as your friends who live next door because we follow our friends’ norms even when they are far away from us.

Gender also can play a role. Some behaviors pass more powerfully through same-sex networks for reasons we still don’t understand. So if your wife is obese, your risk of gaining a lot of weight isn’t greatly enhanced. But if your buddies are obese, your risk is higher.

All this sounds like we have little control over our own behavior. That’s not true. These effects are merely statistical likelihoods. Your genetics, cultural upbringing and individual thinking all play important roles.

How can I use this knowledge to benefit myself? There are a few takeaways I try to remember…

The benefits of a connected life far outweigh the costs. In all my research, I found that the most consistently happy group of people were deeply embedded and centrally located in their networks, which means that they had lots of friends who all had many friends themselves.

Your everyday actions and choices, no matter how small, really are important. For example, it’s very helpful to do what it takes to put yourself in a good mood before you come home at day’s end — because it will make your family happier, which increases the chance of making their friends happier, which radiates outward to touch many people.

Of course, you can make a point to choose happy people to be around. But rather than asking what your social network is doing to you, ask what you can do for it. When you lose weight or quit smoking, it doesn’t just benefit you or your friends and family… it also benefits many other people around you as your behavioral change radiates outward.

Source: Nicholas A. Christakis, MD, PhD, a professor at Harvard University, Cambridge, Massachusetts, with appointments in the departments of health-care policy, sociology and medicine. He is coauthor of Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives (Little Brown). www.ConnectedTheBook.com

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