The concept of behavior being contagious has been around since the 1930's, but it's regaining popularity and finally being backed up by studies and data. The NYtimes article focused on weight gain or loss, smoking and happiness. However, collective behavior has proven pervasive in the recent economic downtown. The explosion of the real estate bubble was largely caused by the herd effect - everyone is just gushing about the importance of "investing in real estate" and the profits you are guaranteed and... how could you not want to be a part of it all? As Felix Salmon of Wired Magazine points out in his article, "Recipe for Disaster: The Formula that Killed Wall Street," the inclination to follow what those around you are doing is so strong that wildly intelligent people that we trusted our money to disregarded statistics and numbers and rationality. The reliance of Wall Street on David Li's formula for correlation contributed significantly to the market crash in 2007.
So what is collective behavior and how does it work? We see our neighbors, friends, family doing something and we're influenced to do the same. I think a great example is smoking (it's much easier to understand than market behaviors). A group of friends has always smoked together; maybe the most rebellious one in the group started when she was 16 and the others soon followed. They all smoke together for years and years. Then one of them decides to quit, then another is influenced by that first one, then another. Pretty soon, only the original girl is still smoking. She feels uncomfortable being the only one lighting up, having to step outside during group dinners because they now sit in the 'non-smoking' section of restaurants. Pretty soon, she too will quit.
This example can be multiplied over and over and over and proven in endless instances. We're seeing it now in our economy. Scientists now have numbers and research to back up this seemingly obvious pattern. However, the problem may now be determining how to break it. After all, how do we pull out of this economic recession when we are all spending less and saving more; when shoppers feel like they have to hide their purchases because no one else is spending. That is the true challenge today.