Medical sociologist Nicholas Christakis gave the keynote speech at the recent Harvard Undergraduate Research Symposium regarding his research on social networks. His talk surveyed the various studies he has conducted, all of which point to the same essential finding: that a slew of behaviors and characteristics, including smoking, obesity, happiness, and even movie preference, can be transmitted from person to person in a social network. This means that your likelihood of smoking, for instance, is not only higher if your friend smokes, but also if his friends smoke, and also if their friends smoke.
This "Three Degrees Rule,” as Christakis puts it in his recent book Connected, holds for other behaviors. For instance, according to one of Christakis’ studies, happiness and sadness can be transmitted quickly and noticeably in a college dorm, where one’s likelihood to be happy depends on how many people, within three degrees of influence, are also happy. For another example, Christakis found that people who identified Pulp Fiction as a favorite movie on Facebook were far more likely to be friends with others who identified it as their favorite movie, but exhibited almost no overlap with the network of those whose favorite film was Love Actually.
Christakis’ research suggests that certain health and social phenomena are, at least metaphorically, epidemic. I asked him after the conference what he thought the "pathogen” might be—that is, by what mechanism do such influences spread? Though he hasn’t specifically researched that question, he believes it largely has to do with the transmission of norms. Seeing your friend smoke alters how acceptable you find smoking, thereby changing your attitude towards the smoking behaviors of your other friends. Christakis admitted there might be other mechanisms as well—for instance, transmission of the actual behavior, or differential patterns of genetic susceptibility.
Nicholas Christakis, MD, PhD, MPH, is Professor of Medical Sociology and of Medicine at Harvard Medical School, and Professor of Sociology in the Harvard Faculty of Arts and Sciences. He is also master of Pforzheimer House.
Tags: Behavior, Positive Psychology, Sociology