considered why friends matter so much. There are at least two possibilities. First, the existence of the social relationship itself may improve your happiness—this is a structural effect of the network on you (the second rule of social networks described in chapter 1). As we discuss in chapter 7, we are hardwired to seek out social relationships, so it is not surprising that we feel pleasure or reward when we spend time with friends and family. Second, friends and relatives make us susceptible to emotional contagion, so our friends’ emotional states affect our own (the third rule of social networks).
While both of these mechanisms probably contribute to people’s happiness, our evidence suggests that contagion may be the more important of the two. We found that each happy friend a person has increases that person’s probability of being happy by about 9 percent. Each unhappy friend decreases it by 7 percent. So if you were simply playing the averages, and you didn’t know anything about the emotional state of a new person you just met, you would probably want to be friends with her. She might make you unhappy, but there is a better chance she will make you happy. This helps to explain why past researchers have found an association between happiness and the number of friends and family. But once we control for the emotional states in one’s friends, we find that having more friends is not enough—having more happy friends is the key to our own emotional well-being.
This does not mean that the structure of the social network is unimportant. Amazingly, it is not just the number of dyadic ties that has an impact; the number of hyperdyadic ties also influences a person’s happiness. When we measured the centrality of each person in the social network, we found that people with more friends of friends were also more likely to be happy. And, more remarkably, this was true even among people who had the same number of direct social relationships. This means that the more friends your friends have (regardless of their emotional state), the more likely you are to be happy.
One might wonder if there is a chicken-and-egg problem here. After all, it is possible to imagine that when we become happier, we tend to attract more friends, and more friends who have lots of friends. This would mean that happiness is driving the network rather than the other way around. But when we examined how the network changes over time, we found that happy people do not tend to become more central. So having a wide social circle can make you happy, but being happy does not necessarily widen your social circle. Being located in the middle of the network leads to happiness rather than the other way around. The structure of your network and your location in it matter.
Given how important direct interaction seems to be for emotional contagion to occur, we also theorized that the effect of the happiness of your social contacts on your emotional state should depend on how near or far they are. The idea is that people who live nearby are more likely to be in contact and therefore more likely to pick up on each others’ moods. Geographic distance can be used as a proxy for frequency of social interaction. In our study, about one in three people live within a mile of their closest friend, but there is a lot of variation, and some friends live thousands of miles apart. We found that when a friend who lives less than a mile away becomes happy, it can increase the probability that you are happy by 25 percent. In contrast, the happiness of a friend who lives more than a mile away has no effect. Similarly, if your spouse lives with you and he or she becomes happy, then your probability of happiness goes up, but spouses who do not live together (because they are separated) have no effect on each other. A happy sibling who lives less than a mile away increases your chance of happiness by 14 percent, but more distant siblings have no significant effect. And happy next-door neighbors also increase your chance for happiness, while neighbors who live farther away (even on the same block) have no significant effect.
All these findings suggest the importance of proximity among people whose emotions influence each other, and the impact of immediate neighbors suggests that the spread of happiness may depend as much on frequent face-to-face interaction as on deep personal connections. While in this case we are considering the spread of a dis-positional state of some duration, these findings are also in keeping with the work on facial mimicry we discussed earlier.
Happiness is thus not merely a function of individual experience or choice; it is also a property of groups of people. Changes in individual happiness can ripple through social connections and create large-scale patterns in the network, giving rise to clusters of happy and unhappy individuals. Since our work was published, similar results on the spread of happiness have been observed in a sample of ten thousand rural Chinese villagers.28 Although we could not observe what causes happiness to spread, a variety of mechanisms are conceivable. Happy people may share their good fortune (e.g., by being pragmatically helpful or financially generous to others), change their behavior toward others (e.g., by being nicer or less hostile), or merely exude an emotion that is contagious. Being surrounded by happy people might have beneficial biological effects too. But whatever the mechanism, it seems clear that we need to change the way we think about happiness and other emotions.
Life on the Hedonic Treadmill
We all know people who are hedonists; they can never get enough of the good life. In fact, lasting happiness is difficult to achieve because people are on a “hedonic treadmill.” Although a change in a person’s circumstances may cause him to be happier (e.g., finding a partner, winning the lottery) or sadder (e.g., losing a job, becoming paralyzed), a broad body of research has shown that people tend to return to their previous level of happiness after such events.29 In fact, studies of lottery winners and spinal cord injury patients reveal that after a year or two, they are often no more happy or sad than the rest of us. Our surprise at this observation stems in part from our inability to anticipate that some things will not change. Lottery winners still have annoying relatives, and paralyzed patients can still fall in love. As psychologist Daniel Gilbert has shown, we tend to focus on only the most salient part of a situation when we are thinking about things that might befall us.30 Moreover, we overlook our ability to adapt to circumstances. So, a person trying to become happier is like someone walking up a downward-moving escalator. Although the effort to climb up and become happier is helpful, it is counteracted by the process of adaptation that forces one back to one’s original state.
Many people try to overcome this problem by intentionally engaging in activities to improve their happiness. We might change our behavior by exercising regularly or by trying to be kind to others or even by avoiding a long commute (which has been shown to be particularly deleterious to happiness). We might change our attitude by pausing to count our blessings or thinking about experiences in the most positive light (as Tibetan monks do). We might also devote effort to causes we find meaningful or strive to achieve important personal goals. Indeed, there is reason to suspect that a sustained effort to engage in such happiness-producing activities might help us progress up the downward-moving escalator.
But in spite of these efforts, each of us tends to stay put in a particular long-term disposition; we appear to have a set point for personal happiness that is not easy to change. In fact, like other personality traits, personal happiness appears to be strongly influenced by our genes. Studies of identical and fraternal twins show that identical twins are significantly more likely to exhibit the same level of happiness than are fraternal twins or other siblings. Behavior geneticists have used these studies to estimate just how much genes matter, and their best guess is that long-term happiness depends 50 percent on a person’s genetic set point, 10 percent on their circumstances (e.g., where they live, how rich they are, how healthy they are), and 40 percent on what they choose to think and do.31 What we experience in life can, of course, change our moods for a period of time, but in most cases these changes are transitory.
What about the network spread of happiness? Does it obey this constraint, only
