How Large Is Your Network? The Power of 2nd and 3rd Degree Connections

Reid Hoffman

December 06, 2012

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Imagine you receive a digital camera with a built-in memory card for your birthday. You bring it on a six-month trip to Africa where you won’t have access to a computer—so all the photos you want to keep must fit on that one memory card. When you first arrive you snap photos freely, and maybe even record some short videos. But after a month or so, the memory card starts filling up. Now you’re forced to be more judicious in deciding how to use that storage. You might take fewer pictures. You might decide to reduce the quality/resolution of the photos you do take in order to fit more. You’ll probably cut back on videos. Still, inevitably, you’ll hit capacity, at which point if you wish to take new photos you’ll have to delete old ones.

Just as a digital camera cannot store an infinite number of photos and videos, you cannot maintain an infinite number of relationships. Which is why, even if you are judicious about your choices, at some point you hit a limit, and any new relationship means sacrificing an old one.

The maximum number of relationships we can realistically manage—the number that can fit on the memory card, as it were—is described as Dunbar’s Number, after evolutionary psychologist Robin Dunbar. But maybe it shouldn’t be. In the early nineties, Dunbar studied the social connections within groups of monkeys and apes. He theorized that the maximum size of their overall social group was limited by the small size of their neocortex. It requires brainpower to socialize with other animals, so it follows that the smaller the primate’s brain, the less efficient it is at socializing, and the fewer other primates it can befriend. He then extrapolated that humans have an especially large neocortex and so should be able to more efficiently socialize with a great number of humans. Based on our neocortex size, Dunbar calculated that humans should be able to maintain relationships with no more than roughly 150 people at a time. To cross-check the theory, he studied anthropological field reports and other clues from villages and tribes in the hunter-gatherer era. Sure enough, he found the size of surviving tribes tended to be about 150. And when he observed modern human societies, he found that many businesses and military groups organize their people into cliques of about 150. To wit: Dunbar’s Number of 150.

But Dunbar’s research is not exactly about the total number of people that any one person can know. The research focused on how many nonhuman primates (and humans, but only by extrapolation) can survive together in a tribe. Of course, group limits and the number of people you can know are closely related concepts, especially if you consider everyone in your life to be part of your social group. Yet most of us define our total social group more broadly than Dunbar did in his research. Survival in the modern world doesn’t depend on having direct, face-to-face contact with everyone in our social network/group, as it did for the tribes he studied.

Regardless of how you parse Dunbar’s research, what is definitely the case is that there is a limit to the number of relationships you can maintain, if for no other reason than the fact that we have only twenty-four hours in each day. But, contrary to popular understanding of Dunbar’s Number, there is not one blunt limit. There are different limits for each type of relationship. Think back to the digital camera. You can either take low-resolution photographs and store one hundred photos in total, or you can take high-resolution photographs and store forty. With relationships, while you can only have a few close buddies you see every day, you can stay in touch with many distant friends if you only email them once or twice a year.

But there’s a twist. While the number of close allies and weak ties you can keep up is limited, those aren’t your only connections. You can actually maintain a much broader social network that exceeds the size of the memory card. It’s by smartly leveraging this extended network that you fully experience the power of I-to-the-We.

Your Extended Social Network: Second- and Third-Degree Connections

Your allies, weak ties, and the other people you know right now are your first-degree connections. A la Dunbar, there are limits to the number of first-degree connections you can have at any one time. But your friends know people you don’t know. These friends of friends are your second-degree connections. And those friends of friends have friends of their own—those friends of friends of friends are your third-degree connections.

Social network theorists use degree-of-separation terminology to refer to individuals who sit within your social network. A network is a system of interconnected things, like the world’s airports or the Internet (a network of computers and servers). A social network is a set of people and the connections that link them. Everyone you interact with in a professional context comprises your professional social network.

Your Network Is Bigger and More Powerful Than You Think

Think of the times you’ve met someone and discovered you know people in common. The clerk at the local hardware store once hiked through Yosemite with your brother-in-law. Your new girlfriend is in the same bowling league as your boss. “It’s a small world,” we say after such realizations. It’s fun to make these unexpected connections. A busy city street can seem awash with strangers, so when we encounter a familiar face, we notice it.

But is the world actually that small? Psychologist Stanley Milgram and his student Jeffrey Travers found that it is. In fact, it’s smaller and more interconnected than the occasional surprising mutual acquaintance might suggest. In 1967 they conducted a famous study in which they asked a couple hundred people in Nebraska to mail a letter to someone they knew personally who might in turn know a target stockbroker in Massachusetts. Travers and Milgram tracked how long it took for the letter to pass hands and reach its destination. On average, it took six different stops before it showed up at the stockbroker’s home or office in Massachusetts. In other words, the original sender in Nebraska sat six degrees apart from the recipient in Massachusetts. It was this study that birthed the Six Degrees of Separation theory, and the credible idea that you share mutual acquaintances with complete strangers on the other side of the world.

In 2001, sociologist Duncan Watts, inspired by Milgram’s findings, led a more ambitious, rigorous study on a global scale. He recruited eighteen targets in thirteen countries. From an archival inspector in Estonia to a policeman in Western Australia to a professor in upstate New York, the targets were selected to be as diverse as possible. Then he signed up more than sixty thousand people from across the United States to participate in the test. They were to forward an email message to one of the eighteen targets, or to a friend who might know one of the targets. Amazingly, factoring in the emails that never made it to their destination, Watts found that Milgram had been right all along: the median distance that separated a participant from a target was between five and seven degrees.

It is a small world, after all. Small because it is so interconnected.

Milgram’s and Watts’s research shows planet Earth as one massive social network, with every human being connected to every other via no more than about six intermediary people. It’s neat to ponder being connected to billions of people through your friends, and the practical implications for the start-up of you are significant as well. Suppose you want to become a doctor and would like to meet a premier M.D. in your specific field of interest. You’ve heard that getting an introduction is the only way you’ll be able to meet her. The good news is that you know that you are at most only six degrees away from her. The bad news is that following Milgram’s or Watts’s procedure—asking one good friend to forward an email and hope that six or seven email forwards later the email will arrive at the target’s computer—is neither efficient nor reliable. Even if it does arrive, the introduction would be highly diluted. Saying you’re a friend of a friend of a friend of a friend of a friend of a friend doesn’t quite carry enough heft to open doors.

But if there were a master chart of the entire human social network, you could locate the shortest possible path from you to the doctor. Now, increasingly, there is. Out of an estimated one billion professionals in the world, well over 170 million of them are on LinkedIn. Now, you can search this network to find the connections and friends of connections who can introduce you to that all-star doctor with the fewest number of handoffs. You don’t need to randomly forward an email and hope it arrives at your destination after six twists and turns.

Here’s where the caveat to the Six Degrees of Separation theory comes in. Academically, the theory is correct, but when it comes to meeting people who can help you professionally, three degrees of separation is what matters. Three degrees is the magic number because when you’re introduced to a second- or third-degree connection, at least one person in an introduction chain personally knows the origin or target person. In this example: You—> Karen—> Jane—> Sarah. Karen and Jane are in the middle, and both of them know either You or Sarah—the two people who are trying to connect. That’s how trust is preserved. If one additional degree of separation is added, a person in the middle of the chain will know neither You nor Sarah, and thus have no stake in making sure the introduction goes smoothly. After all, why would a person bother to introduce a total stranger (even if that stranger is a friend of a friend of a friend) to another total stranger?

So, the extended network that’s available to you professionally doesn’t contain the roughly seven billion other humans on the planet who sit six degrees away. But it does contain all the people who sit two or three degrees away, because they are the people you can reach via an introduction. This is a large group. Suppose you have 40 friends, and assume that each friend has 35 other friends in turn, and each of those friends of friends has 45 unique friends of their own. If you do the math (40 × 35 × 45), that’s 54,000 people you can reach via an introduction.

Now you know why one of LinkedIn’s early marketing taglines was: Your Network Is Bigger Than You Think. It is!

Adapted from my book with Ben Casnocha titled The Start-Up of You: Adapt to the Future, Invest in Yourself, and Transform Your Career.