Social contagion is the spread of thoughts, emotions, and behaviors from person to person and among larger groups as affected by shared information and mimicry.
Paul M. Kirsch, “The Influence of Social Contagion and Technology on Epidemic Non-Suicidal Self-Injury,” 2012.
The Spread of Obesity: An Example of Social Contagion
Social contagion actually may account for as much, or perhaps, even more of a person’s risk of obesity than genetic and other factors that have been previously studied.
Academic research shows that, at least in the American population, and maybe in the international population as well, that we are all connected to one another by six degrees of separation. Your friends’ friends’ friends’ friends’ friends’ friend, for example, is going to include just about everybody in the population. And what we find, remarkably in the study, is that although the average degree of separation between individuals is six, here your influence extends up to three degrees of separation. And so, halfway, pretty much half the distance into the social network, your health behavior is having an impact on other people.
–Dr. James Fowler in “Obesity and Social Networks – CBS.”
Mindless Eating – Explaining Obesity in Terms of Social Contagion
Image: "TransparencyCamp 2012 - #tcamp12 social network graph [1/2]" by justgrimes.