contacts of their own. Do this a few more times, and you’ve reached nearly every person on the planet. That, simply put, is the concept of six degrees of separation.
But knowing the social distance from one individual to another is far from the complete picture. Over the past several decades, network science has developed a far more detailed, though still incomplete, picture of our social interactions. We now understand mathematically why the most popular person in a network has so many more friends than the next most popular person, and wehave measured the average number of close social connections each person maintains on a regular basis (it’s about four). We understand how social groups are distributed across countries, and even how we make and break friendships over time. In these ways, and many more, we are beginning to truly understand the social structures that we are embedded in, and how these ties influence us.
Some of the most cutting-edge research that is going on right now is devoted to understanding how our connections influence us, and how things spread. As a postdoc I worked in the laboratory of Nicholas Christakis, one of the giants in this field. If you don’t recognize his name, you may remember some of the
New York Times
headlines about work done by him and his longtime collaborator James Fowler: “Are Your Friends Making You Fat?”; “Find Yourself Packing It On? Blame Friends”; “Study Finds Big Social Factor in Quitting Smoking”; “Strangers May Cheer You Up, Study Says.”
What these researchers have found, in study after study, is that our actions have consequences that ripple across our social web to our friends, our friends’ friends, and even our friends’ friends’ friends.
But just as health behaviors spread, so do facts and bits of knowledge. Since information spreads through social rather than physical space, it is vital that we understand social networks and how they operate. In this globalized age, where we can be anywhere on the planet within a day or so, the ties we have to those we know, rather than where we are, take on greater meaning. Whether we are advertisers trying to gain an advantage in the marketplace, or even just want to lose a few pounds, we crave the answers to a whole host of new kinds of questions about networks. A sample of such questions:
How does each sort of tie that we have to those around us—whether friend, relative, spouse, neighbor—affect the spread of each individual fact or even each behavior? Are our social ties related to distance, which could have an effect on how information spreads?What do the structures of people’s social networks look like, and do the shapes of these networks—regular, random, or something in-between—affect how we interact? And are our social ties, such as how many friends we have, and even how likely our friends are to know one another, affected by the genes inside us?
All of these questions are beginning to be asked, and answered, by network scientists. In our specific concern, network scientists have recently begun to explore certain cases where facts spread, or don’t spread, and how this works.
. . .
BACK in the 1970s a sociologist named Mark Granovetter created a simple little thought experiment: He imagined each social connection between people as having one of two strengths—weak or strong. Strong ties are those that we have to our parents, our spouses, or our close friends. Weak ties are those that we have with friends from high school or college to whom we seldom speak. Or to the acquaintance at work whom we banter with but don’t generally speak to outside the office. Or, in the modern age, most of our Facebook “friends.”
Granovetter’s thought experiment: If we have only these two connection strengths, simplistic though that may be, what should our social networks look like? He argued that if two of our friends are close to us, it is very likely that they will know each other,
But knowing the social distance from one individual to another is far from the complete picture. Over the past several decades, network science has developed a far more detailed, though still incomplete, picture of our social interactions. We now understand mathematically why the most popular person in a network has so many more friends than the next most popular person, and wehave measured the average number of close social connections each person maintains on a regular basis (it’s about four). We understand how social groups are distributed across countries, and even how we make and break friendships over time. In these ways, and many more, we are beginning to truly understand the social structures that we are embedded in, and how these ties influence us.
Some of the most cutting-edge research that is going on right now is devoted to understanding how our connections influence us, and how things spread. As a postdoc I worked in the laboratory of Nicholas Christakis, one of the giants in this field. If you don’t recognize his name, you may remember some of the
New York Times
headlines about work done by him and his longtime collaborator James Fowler: “Are Your Friends Making You Fat?”; “Find Yourself Packing It On? Blame Friends”; “Study Finds Big Social Factor in Quitting Smoking”; “Strangers May Cheer You Up, Study Says.”
What these researchers have found, in study after study, is that our actions have consequences that ripple across our social web to our friends, our friends’ friends, and even our friends’ friends’ friends.
But just as health behaviors spread, so do facts and bits of knowledge. Since information spreads through social rather than physical space, it is vital that we understand social networks and how they operate. In this globalized age, where we can be anywhere on the planet within a day or so, the ties we have to those we know, rather than where we are, take on greater meaning. Whether we are advertisers trying to gain an advantage in the marketplace, or even just want to lose a few pounds, we crave the answers to a whole host of new kinds of questions about networks. A sample of such questions:
How does each sort of tie that we have to those around us—whether friend, relative, spouse, neighbor—affect the spread of each individual fact or even each behavior? Are our social ties related to distance, which could have an effect on how information spreads?What do the structures of people’s social networks look like, and do the shapes of these networks—regular, random, or something in-between—affect how we interact? And are our social ties, such as how many friends we have, and even how likely our friends are to know one another, affected by the genes inside us?
All of these questions are beginning to be asked, and answered, by network scientists. In our specific concern, network scientists have recently begun to explore certain cases where facts spread, or don’t spread, and how this works.
. . .
BACK in the 1970s a sociologist named Mark Granovetter created a simple little thought experiment: He imagined each social connection between people as having one of two strengths—weak or strong. Strong ties are those that we have to our parents, our spouses, or our close friends. Weak ties are those that we have with friends from high school or college to whom we seldom speak. Or to the acquaintance at work whom we banter with but don’t generally speak to outside the office. Or, in the modern age, most of our Facebook “friends.”
Granovetter’s thought experiment: If we have only these two connection strengths, simplistic though that may be, what should our social networks look like? He argued that if two of our friends are close to us, it is very likely that they will know each other,
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