
The Isolation of Social Media
Social media should promote conversation and exchange, yet increasingly it doesn't
Though the United States accounts for only about 4 percent of the global population, it leads the world in COVID-19 cases and deaths, and among high-income countries is behind only Russia in vaccine opposition. Studies find that anywhere from 8 to 22 percent of the population remains unwilling to get jabbed, despite the reams of data and anecdotal evidence showing the shots are overwhelmingly safe and effective.
Early in the pandemic, this hesitancy could have been partly accounted for by the fact that “denial and superstition are typical human responses to plague,” according to Nicholas Christakis, MD ’89, director of the Human Nature Lab at Yale University and co-director of the Yale Institute for Network Science. But a larger effect comes from the ways in which behaviors, attitudes, and emotions spread among members of a group, moving as fast as and often as virulently as any biological pathogen. A 2021 study by the Center for Countering Digital Hate, an international nonprofit that works to stop online hate and misinformation, showed that two-thirds of content opposing vaccines and vaccination shared on Facebook and Twitter originated from just 12 people, which is in keeping with research Christakis has done on how information advances through time and space.
“A very deep and fundamental principle of human social networks is that they magnify whatever they are seeded with,” Christakis says. “They don’t give rise to things. But once you put something into the network, the network will make more of it. If you put Nazism into the network you get more Nazis; if you put love into the network you get more love. If you put antivaccine sentiment into the network, what’s going to happen?”
All together now
Social scientists first postulated that relationships matter to an individual’s health in the late 1800s, but it wasn’t until 2009 that the all-encompassing effects of relationships entered the public consciousness, as a result of Christakis’s book Connected, co-written with James Fowler, a political scientist at the University of California San Diego. In it, the authors show how people you don’t even know influence nearly every aspect of your life, from behaviors like smoking, drinking, voting, cooperation, and divorce to conditions like obesity to attitudes like happiness or vaccine acceptance. “If your friends are obese, your risk of obesity is higher,” Christakis explains in a 2010 TED Talk. “If your friend’s friends are obese your risk of obesity is 25 percent higher.” It’s only when you get to your friend’s friend’s friend’s friends, he continues, “that there’s no longer a relationship between that person’s body size and your own body size.”
This association could be due to homophily, in which birds of a feather flock together, so to speak, or to confounding, in which you and your friend’s friends might share a common exposure to, say, a new pizza place down the street. A key effect, however, comes from induction, in which weight gain becomes a norm—it’s simply more acceptable within the group. “We found that if your friend becomes obese it increases your risk of obesity by about 57 percent in the same given time period,” Christakis says. Recognizing some of the possible ramifications of these findings, Christakis points out it would be a misuse of the findings to justify prejudice against people with larger body sizes.
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The more Christakis and Fowler studied social networks, the more they came to see them as living things independent of the individuals who comprise them. “This network that’s changing across time has a memory,” Christakis says in the TED Talk. “It moves; things flow within it. It has a kind of consistency; people can die but it doesn’t die. … It has a kind of resilience that allows it to persist across time.” In the 1960s the Harvard social psychologist Stanley Milgram showed that we are each separated by an average of six connections from everyone else in the world. To that proposition, which inspired the 1990 play Six Degrees of Separation and the 1993 film of the same name, Christakis and Fowler added the finding, since replicated many times over, that we each have three degrees of influence—on our friends, their friends, and their friends’ friends.
Hive behavior
“Human brains are designed to function in concert with other human brains,” says Ian Corbin, an HMS research fellow in neurology at Brigham and Women’s Hospital, co-director of the hospital’s Human Network Initiative (HNI), an interdisciplinary research center, and senior fellow at Capita, a think tank. “That is our optimal form of cognition, and if you pull us out of social contexts of intersubjective feedback loops, our brains have to work harder.”
“Behaviors require a complicated mix of dense ties that are designed to reinforce shared knowledge and practices, but also loose ties that allow access to dissimilar knowledge.”
Amar Dhand, MD ’08, an HMS associate professor of neurology and Corbin’s co-director at HNI, explains how this came about. For millions of years, when population numbers were low, hominid brains grew steadily larger, until around the Neolithic period in the Stone Age, when complex societies began to emerge. “The Neolithic human brain shrank compared to its evolutionary ancestors, while perhaps becoming more sophisticated internally to maintain cognitive capacity,” Dhand says, adding that the metabolism and energy that might have been required by a larger brain could then be reallocated to endurance and other adaptive functions. “Neolithic humans had to be hyperaware of threats because they were in very small groups or maybe alone in the wild most of the time, which would create an incredible stress response,” he says. “The fact that you could now be interdependent and rely on friends to be watching for threats too would reduce your cortisol level and contribute to an increased life span for the next step on the evolutionary tree.”
Social networking also frees up energy previously devoted to cognition. “If you’re a trusted co-perceiver of mine,” Corbin says, “then my brain has to do less work than if I have to arrive at solutions by myself.” And it allows for behaviors that can be understood only by studying the collective, Christakis points out, as when a hive of bees finds a new nesting site or a school of fish evades a predator. Examples like this, he says, “require a complicated mix of dense ties that are designed to reinforce shared knowledge and practices, but also loose ties that allow access to dissimilar knowledge. The ability to exploit your environment is enhanced by your close ties. But what happens when the well goes dry and no one among us knows where new water is to be found? There has to be a trade-off between intensity and novelty, and networks have optimized that.”
Real/unreal/constructed
“All reality is social reality,” writes Jay Van Bavel, an associate professor of psychology and neural science at New York University, in his book The Power of Us, coauthored with Dominic J. Packer, a professor of psychology at Lehigh University. But how do individuals come to identify with the thinking of a particular group?
“Children develop their understanding of the world in a feedback loop with their caregivers,” Corbin says. “Staying embedded with people who share your assumptions is the easiest and most comfortable thing. Sometimes this begins to change when you start to see the world and have other experiences. You might look around and be like, ‘I think my parents and their community are missing some stuff. My friends at school seem to get it.’ That’s when you may break off and go into other groups.”
Not only do your circumstances at birth and your foundational friendships affect what you believe, but thanks to magnetic resonance imaging, scientists now know that your brain structure may play a role. While correlation doesn’t necessarily equal causation, we know that environment can help shape brain structure.