guest post by Brian G. Southwell In August 2013, the Associated Press reported that one’s success in getting a liver transplant in the United States is partially a function of geography and social space: because of disparities in the current transplant district system, where a person lives dictates in part whether they will receive a needed transplant. In my own work, I’ve also found disparity between communities in medical service distribution. In a different story, researchers have found that the spread of obesity seems linked to social network patterns, such that one’s chance of becoming obese rises if she or he has a friend who also becomes obese. All of this suggests that spatial disparity, particularly that related to one’s social networks, impacts health and well-being. A key question, however, involves mechanism: How exactly is it that the social composition of one’s living space, broadly conceptualized, matters in explaining access to health or health outcomes? In case of the liver transplant story, social space matters because you typically need to live within reach of an available organ in order to receive a transplant and some places have more or less supply or demand. In other instances, however, the story sometimes involves social interaction, including discrepancy in the willingness or ability of people you know to share health-related information with you. That we live in a world of continued segregation, whether de facto or de jure, is not a new observation and continues to merit policy initiatives or other large-scale efforts. Some of these efforts might stem from the commercial sector: Facebook CEO Mark Zuckerberg recently announced the company’s intention to get all of the world’s population on-line (and ostensibly registered with Facebook). Would allowing everyone in the world to have a Facebook account address disparities in health and well-being, however? Chances are that such global participation on a social media site would not offer a panacea. After all, some of the discrepancy between people in their experience and understanding of health also involves diversity in network interactions that are beyond the scope of the law or efforts to increase the simple availability of social media tools, per se. Ideas are not shared or repeated or explored equally in all social circles for many reasons, in part because the social infrastructure for interpersonal engagement differs from one person’s network to another’s network. This is not to say that everyone’s social networks are not generally similar in some ways. We all can be characterized as living among a network or networks in some fashion, and researchers have found that social network tendencies are similar in hunter-gather societies and in larger service-based economies alike. In many animal networks, for example, some nodes are more well-connected than others; patterns like that occur again and again. That said, the size, scope, and sharing tendencies of those who regularly surround a person also vary between people and between the social groups in which they live. Our repeated rediscovery that health-related disparities between people exist increasingly should shed light on the differences in the networks to which we have access, collective differences that might warrant our attention as much as individually-focused considerations. To ignore that and focus only on excitement regarding new media technologies for connection is probably a misstep. Brian Southwell is Senior Research Scientist at RTI International as well as a member of the faculty at the University of North Carolina at Chapel Hill and Duke University. His new book, Social Networks and Popular Understanding of Science and Health: Sharing Disparities, is now available from Johns Hopkins University Press and major online retailers. Watch the book trailer here.