What do behavioral traits and infectious diseases have in common? According to researchers James Fowler and Nicholas Christakis, quite a bit. Let’s suppose that in your thirties, you become obese. We might assume that your jelly donuts and lack of exercise has finally caught up with you. Fair enough.
What might surprise you is the contagious effect your new weight is having on your peer group.
Your friends are 57% more likely to gain weight as a result of hanging out with you. Not only that, but their friends, the ones not in your immediate circle, are 20% more likely to gain weight as well.
The same contagious effect seems to be true about smoking. According to Massimo Pigliucci in Answers for Aristotle, quitting smoking means “your friends have a 67% chance of quitting too, and their friends a 36% chance; this is also true of alcoholism, depression, and the effect is even present for happiness (meaning subjective well-being) itself!”
‘Wait a minute,’ your rational brain might already be protesting, ‘there’s no cause and effect here, but mere correlation. After all, aren’t my friends probably living in a similar socio-economic bracket, therefore frequenting Dunkin Donuts too, essentially living my lifestyle?’
From that perspective, it would stand to reason that you’d see similar tendencies in your friends across the board. Yet Fowler and Christakis were able to document that the patterns of change aren't simultaneous. They happen over time, like the spreading of a disease.
And if habits broke down purely on socio-economic lines, then your address would be one of the best indicators of your behavior. Surely if any collection of people could be expected to act the same, it would be those with access to the same grocery stores, gyms, bars, and restaurants. However, the behavior of your friends is a much better predictor, even if your friends live across town.
Why? Mimicry is an essential aspect of our lives. The association and comfort of being part of a group is well documented. And what is a group if not individuals brought together by shared experiences, held together by commonality?
As Fowler and Christakis discuss, these commonalities go beyond a nicotine habit or a number on a scale. One of the traits that seems the most influenced by who you spend time with? Happiness. Seventies acoustic troubadour Cat Stevens once sang, “If you want to live high, live high, and if you want to live low, live low" but these studies suggest you might first want to seek out other pals who are living how you want to live.
If Fowler and Christakis are correct and behavioral traits can spread like the common cold, the idea of frequent hand washing, and general accountability for one's disposition, take on a whole new significance.