Show Coverage: Cooperative behavior is contagious

Three degrees of separation is all it takes to influence good or bad behavior-whether it's making poor health choices or simply being happy, said Nicholas Christakis, MD, professor, departments of Health Care Policy, Medicine and Sociology, Harvard University.

“Laboratory evidence indicates that cooperative behavior is contagious,” he said.

Dr. Christakis' research has shown that actions not only affect close friends but also have a ripple effect on others, especially in networks where people socialize.

“Social networks are a means of magnifying behaviors,” he said.

Offline, traditional social networks are being overshadowed by the Facebooks and Twitters of the 21st century. He said that individuals are all influenced by other members of a group to which they belong, even if it is comprised of close friends and not-so-close friends. 

Dr. Christakis extended his theory to physician networks, indicating that when these providers share patients or specialties, they are more apt to influence each other’s behavior. These ties are what he anticipates will crate accountable care organizations.

However, the greater a person’s circle of influence is in a social network, the more power he or she has in attracting others to the same behavior. For example, those who don't smile will float to the periphery.

“Clustering is more than chance,” Dr. Christakis said.  “It can be a domino effect; you gain weight so I gain weight. It's a ‘birds of a feather flock together’ phenomenon," he said.

Finally, it could be a matter of joint exposure. Two individuals might go to the gym and keep their weight down or together might be lured by the fast food environment.

To make social networks effective, he said, they need to be or feel real, have something at stake, have both leaders and followers and reinforce behavior.