The average lifespan of a friendship? 10 years. Here’s why. | Nicholas Christakis

This is the psychology of why friendships (and marriages) fail. - Some friendships last a lifetime, but most have a lifespan. In the U.S., best friends tend to last for 10 years on average, says Nicholas Christakis. - In friendships, one person may begin to defect or "free ride", which causes the other person to choose between cooperation or defection. People tend to choose the latter so they won't be taken advantage of. - A certain amount of social fluidity, taking a breather from a friendship, can actually make a friendship last longer. Nicholas A. Christakis is a physician, sociologist, and director of the Human Nature Lab at Yale University, where he is the Sterling Professor of Social and Natural Science. His most recent book is Blueprint: The Evolutionary Origins of a Good Society (https://amzn.to/2VpXp3S). Follow him on Twitter @NAChristakis Read more at BigThink.com: http://bit.ly/2FO34tS Follow Big Think here: YouTube: http://goo.gl/CPTsV5 Facebook: http://bit.ly/1qJMX5g Twitter: https://twitter.com/bigthink