Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health

Happiness and other emotions and behaviours are contagious

Happiness is contagious, spreading among friends, neighbours, partners and family. A large study (1) for the first time shows how happiness and other emotions can copy through clusters of people who may not even know each other. We are influenced by the moods of friends of friends, and of friends of friends of friends - people up to three degrees of separation away from us who we have never met.

You increase the likelihood that you will be happy by being better connected to happy people. "Most people will not be surprised that people with more friends are happier, but what really matters is whether those friends are happy," says Nicholas A. Christakis, a medical sociologist at Harvard Medical School in Boston, who has pioneered much of this work. "You would think that your emotional state would depend on your own choices and actions and experience, but it also depends on the choices and actions and experiences of other people, including people to whom you are not directly connected. Happiness is contagious" said Christakis.

But choose your friends carefully. Many other traits, both good and bad, spread among friends. Christakis's studies have shown that in addition to happiness, a whole range of other characteristics are transmitted through networks of friends in ways that are not entirely understood. Obesity, depression, drinking alcohol, smoking and the tendency to quit, ill-health, the inclination to turn out and vote in elections, a taste for certain music or food, a preference for online privacy, even the tendency to attempt or think about suicide ripple through networks "like pebbles thrown into a pond", says Christakis. An earlier study in England showed that your risk of attempting suicide is four times higher if you have a friend who has tried to kill him/herself. (6)

The idea that we can be influenced by the moods, habits and state of health not only of those around us, but also those we do not even know may at first seem alarming. It implies that we have little control over our emotions and behaviours, since most social influence operates at a subconscious level. However, Duncan Watts, a sociologist at Columbia University, New York says: "Social influence is mostly a good thing. We should embrace the fact that we're inherently social creatures and that much of who we are and what we do is determined by forces that are outside the little circle we draw around ourselves."

The Happiness Effect

One person's happiness can affect another's for as much as a year, the researchers found.

When one person in a network became happy, the chances that a friend, sibling, spouse or next-door neighbour would become happy increased by between 8% and 34%. The effect continued through three degrees of separation, dropping progressively from about 15% to 10% to about 6%.

While obesity appeared to spread even among people who lived far apart, happiness appears to be transmitted only among people who live within a mile of one another. The influence was also greatest among people who considered themselves mutual friends.

Unhappiness also appeared to be catching, but not as strongly. An unhappy connection increased the chances of being unhappy by about 7%, while a happy connection increased the chances of being happy by about 9%. While having more friends is important for your happiness, the benefit of having more friends appears to be lost if they are unhappy.

Mimicry

All this poses a key question: how can something like happiness be contagious? Some researchers think one of the most likely mechanisms is empathetic mimicry. Psychologists have shown that people unconsciously copy the facial expressions, manner of speech, posture, body language and other behaviours of those around them, often with remarkable speed and accuracy. This then causes them, through a kind of neural feedback, to actually experience the emotions associated with the particular behaviour they are mimicking. Actions and feelings can be as contagious as a virus.

Barbara Wild and her colleagues at the University of Tubingen, Germany (2), have found that the stronger the facial expression, the stronger the emotion experienced by the person observing it. She believes this process is hard-wired, since it acts so rapidly and automatically.

Elaine Hatfield at the University of Hawaii, Honolulu (3) suggested it works through the action of mirror neurons, a type of brain cell thought to fire both when we perform an action and when we watch someone else doing it. Unconscious imitation lets people "feel a pale reflection of their companions' actual emotions" and even "feel themselves into the emotional lives of others", she says.

The strength of the infection

How susceptible you are to someone else's happiness depends on the nature of your relationship with them. For example, if a good friend who lives within a couple of kilometres of you suddenly becomes happy, that increases the chances of you becoming happy by more than 60%. In contrast, for a next-door neighbour who is not a close friend the figure drops to about half that, and someone living a few tens of metres away in the same block may have no effect. A nearby sibling may only have a 15% effect, and surprisingly, a cohabiting partner makes a difference of less than 10%.

Two factors appear crucial: the frequency of social contact, and the strength of the relationship. This is not too surprising: we know that emotional contagion requires physical proximity. It is also likely that the closer we feel to someone, the more empathetic we are towards them, and the more likely we are to catch their emotional state.

The researchers were confident that the happiness was not the result of living in the same good neighbourhood, because they did not find the effect for people living on the same block beyond a next-door neighbour. The researchers also ruled out another possibility that happy people tend to be drawn to each other, because people tended to get happier if someone they knew became happy.

Obesity

We can pick up and pass on a variety of other behaviours through our social networks. Your risk of gaining weight increases significantly when your friends gain weight. "Obesity appears to spread through social ties," Christakis says. Your likelihood of putting on weight depends on who you are interacting with; after controlling for factors such as difference in socioeconomic status, the researchers found that an individual's chances of becoming obese increased by 57% if one of their friends became obese, 40% if a sibling did and 37% if their spouse did, irrespective of age (4).

Neighbours have no influence on your probability of obesity, and how far away you live from a friend counts for little, which implies that obesity spreads via a different mechanism to happiness. Rather than behavioural mimicry, the key appears to be the adoption of social norms. In other words, as I see my friends gain weight, it changes my idea of what an acceptable weight is. One similarity with happiness is that friends and relatives have a far greater influence on obesity if they are of the same gender. "Women look at other women, men look at other men," says Christakis. This could also help explain the epidemic of eating disorders reported among groups of schoolgirls in recent decades.

Christakis found that when people stop smoking, they usually do so along with whole clusters of friends, relatives and social contacts. As more people quit, it becomes the socially acceptable thing to do, and those who choose to continue smoking become less popular in the group. People are most strongly influenced by those closest to them: if your spouse quits, it is 67% more likely that you will too. Your work colleagues can also have an effect, particularly if you are in a small close-knit workplace. More highly educated friends influence each other more than the less educated. (5)

Happiness, obesity, smoking habits and many other activities that we traditionally think of as shaped by individual circumstances, turn out to be influenced by social connections. For example, in 2004 Peter Bearman at the Institute for Social and Economic Research and Policy at Columbia University uncovered a link between suicidal behaviour and certain friendship patterns (American Journal of Public Health, vol 94, p 89). He is now looking at whether the recent rise in the diagnosis of autism may be socially determined, and says his findings could be "explosive". "It is likely that if you have an autistic child in your community the probability of your child being diagnosed with autism is significantly higher.

Many factors contribute to the architecture of our social networks and our position in them: where we live, our ethnic background, family size, religion, where we work, education, income, our interests, and our tendency to gravitate towards people similar to us. Research by Christakis's team suggests there is also a strong genetic component. They compared the social networks of identical and fraternal twins, and found that identical twins had significantly more similar social networks than fraternal twins. That may not sound so remarkable, since personality traits such as gregariousness and shyness clearly play a role in determining how connected we are. But there is more to it, says Christakis. "It's not just about having a genetic predilection to be friends with a lot of people, it's about having a genetic predilection to be friends with a lot of popular people.

Some researchers liken the "collective intelligence" of social networks to the flocking of birds. For example a decision to quit smoking is no more of an isolated move than the decision by a bird in a flock to dart off to the right.

Duncan Watts at Columbia University has shown that seeding social groups with certain ideas or behaviours can lead to those ideas copying across entire global networks. He says that the key for the spread of anything from happiness to the preference for a particular song is a critical mass of interconnected individuals who influence one another.

It is unlikely we can escape these social influences entirely. "Even when you're aware of it, you're probably susceptible," says Watts. But by being aware of these effects of social infection we may be able to counter them, or use them for our own benefit. "There's no doubt people can have some control over their networks and that this in turn can affect their lives," says Christakis.

Tips for a healthier social network:

Choose your friends carefully.
Actually cutting ties with old friends might be a bit drastic, but spend less time with those who have traits you would prefer not to have - lazy people, perhaps, or those inclined to negative thinking. And beware of those who hang out with such people even if they do not display their views or behaviours - remember the three degrees of separation.
Join a club whose members you would like to emulate (tennis, singing, meditation), and importantly, socialise with them.
If you really can't avoid spending time with certain people whose behaviours or emotional state you would rather not take on board (perhaps some relatives at family gatherings), then try to avoid the natural inclination to copy their postures and facial expressions - but be prepared for them to be instinctively cool towards you as a result.
Be aware at all times of the power of social influence - and remember that being a social animal is mostly a good thing.

Aging and the effect of your friends

The researchers did not examine the effect of your friends on your rate of aging. However, after reading the above it seems obvious that your social networks will be a major factor affecting your aging. If you have close friends of the same age and background, with many similarities to yourself, and you see them aging, all the above mechanisms will come into play to affect your own rate of aging. As I discuss in detail in Grow Youthful, you can consciously age at a slower rate if you disengage from society's norms and the influences of those around us.

References

1. Nicholas A. and co-author James H. Fowler. Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study. British Medical Journal 4 December 2008; DOI: 10.1136; 337:a2338.
They looked at networks of friends, relatives, neighbours and work colleagues among 4,700 people in the Framingham Heart Study, an ongoing multi-generational epidemiological survey that has tracked risk factors in cardiovascular disease among residents of Framingham, Massachusetts, since 1948.

2. Nicholas A. Christakis, James H. Fowler. Psychiatry Research, vol 102, p 109

3. Nicholas A. Christakis, James H. Fowler. The Social Neuroscience of Empathy, April 2009

4. Nicholas A. Christakis, James H. Fowler. The New England Journal of Medicine, vol 357, p 370

5. Nicholas A. Christakis, James H. Fowler. The Collective Dynamics of Smoking in a Large Social Network. The New England Journal of Medicine, 22 May 2008; 358:2249-2258. 2008DOI: 10.1056/NEJMsa0706154.

6. Norman Kreitman, Peter Smith, Eng-Seong Tan. Attempted Suicide in Social Networks. Brit. J. prev. soc. Med. (1969), 23, 116-123.

Your Friends, And Their Friends Can Affect Your Emotions