We are, it is widely appreciated, not solitary creatures. What is less appreciated, however, is that we are social in a particular kind of way: we do not just get together in groups, we form networks. While a group is simply a collection of people (either an abstract one, like "lawyers" or "CSW students," or a particular one, like "those people over there, who I am pointing to, waiting to get in to the concert"), a network
is something more. In addition to the people involved, a network also contains the particular person-to-person ties that bind them.
We've always been embedded in networks, long before Facebook and MySpace burst on the scene, at least since we emerged from the African savanna. Studies of identical and fraternal twins demonstrate that there is even a genetic basis for human social networks. And the reason we are embedded in a web of connections is that we benefit from them. Through them, we can coordinate our actions — killing a mastodon, organizing a defense, or creating an online wiki. Networks do this by allowing us to influence and inform others, both people we are directly tied to and even people we do not know personally but who know someone we know.
One of the most basic observations about networks, in fact, is that diverse phenomena — whether information, emotions, germs, or money — diffuse through them. And each person influences others (and is influenced by others) up to three degrees of separation (i.e., up to their friends' friends' friends). Whether you gain or lose weight, start or stop smoking, become happy or sad, go to the polls or abstain: all these activities depend, in part, on the similar behaviors of your friends, your friends' friends, and even your friends' friends' friends, but generally not further. We call this the "Three Degrees of Influence Rule," and it has its origin in a number of fundamental social and biological properties of social networks.
One explanation for this rule is that information generally becomes less precise as it is transmitted, feelings become less intense, and motivations become less strong. One study of people looking for a piano teacher, for example, shows that piano teachers get the majority of their clients from other clients who are within three degrees of separation from them. And our own work indicates that your weight, smoking behavior, and happiness are influenced by your friends, your friends' friends, and your friends' friends' friends. But beyond that point, the influence becomes negligible.
Yet this fundamental observation about human social networks pertains only to natural social networks. In their ingenuity, humans have invented ways to circumvent nature by creating artificial networks. These networks differ from natural networks in three ways: (1) they have a totally different structure; (2) they tend to be organized for a specific purpose that everyone within them is aware of; and (3) they often have mechanisms to foster or preserve communication between connected people. The contrast between the two types of networks can be appreciated by comparing the structure of the two networks below. One (on the top) is a natural network of 105 college students, and the other (on the bottom) is an artificial network of 100 people organized into a telephone tree of the kind used in every town in America to disseminate news about school closings. Each circle is a person, and each line connecting them is a tie between two people. In the case of the telephone tree, the lines are arrows, indicating the "direction" of the relationship and the flow of information, whereas in the natural social network shown, the relationships are two-way.
One way to think about these artificial networks is that we have taken over the power of social connections and used it for our own ends. We exploit a natural architecture by harnessing it — much as we might build a windmill to exploit the wind. With artificial networks, we can expand our influence, and break beyond the ordinary, natural constraints that limit our influence to three degrees.
For example, even human body organs can "flow" through networks, from person to person to person. John Lavis, a 62-year old resident of the town of Mississauga, Ontario, father of four and grandfather of three, was dying of heart failure in 1995. His own heart had failed during triple bypass surgery, and he was placed on a temporary artificial heart. In a stroke of unbelievable good fortune, a donor's heart was transplanted into him just eight days later when he was on the brink of death. His daughter recalled: "We were a family of immense gratitude.... [My father] received the biggest gift he will ever receive — his life was given back to him." Motivated by this experience, Lavis's children all signed donor cards, thinking that this symmetrical act was the least they could do. And then, in 2007, Lavis's son Dan died in a work-related accident. Eight people benefited from his decision to donate organs. The woman who received his heart later wrote to the Lavis family, thanking them for "giving her a new life."
But when the network is organized, the spread can be much, much greater. For example, the same year that Dan Lavis donated his organs, physicians in the U.S. organized a cascade an amazing ten links long. With a little help from doctors, Adam gave one of his kidneys to Betty, and Betty's sibling Charlie gave one of his kidneys to David, and David's spouse gave one of her kidneys to Edward, and then Edward's sibling gave one to Frank, and so on.
Similarly, most information that is passed from person to person in a natural setting gets garbled. But when the process is managed and the stakes are high, people can transmit information accurately across great distances. For example, the longest successful whisper chain (the children's game of telephone) involved 56 links and successfully transmitted a marriage proposal to an unsuspecting bride. Ordinarily, we are not aware of something said by a person 56 degrees removed from us (and, in any case, it is true that any two people on the planet actually have roughly a mere six degrees between them). But with the right kind of network, we can be.
It is the ties that make a network different from a mere group. And it is the ties that help explain how, when it comes to human activity, the whole can be greater than the sum of its parts. It is exactly this emphasis on the relationships between people — on how we are connected naturally, artificially, biologically, and technologically — that we illuminate in our new book, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives. Why do humans form social networks? What role do they play in our lives? What purpose do they fulfill? And how can we harness their power for the better?