This piece is from a new PopTech Edition about harnessing social contagion for social good. Visit for more interviews, essays and videos with leading thinkers on this subject.
We naturally imitate the people around us, we adopt their ideas about appropriate behavior, and we feel what they feel. Acts of charity are no exception. In our 2010 generosity experiment (PDF), we showed that every extra dollar of giving in a game designed to measure altruism caused people who saw that giving to donate an extra twenty cents.
That same experiment showed that contagious generosity spreads up to three steps through the network (from person to person to person to person), and when we added up all the extra donations that resulted at every step, we found that an extra dollar in giving yielded three extra dollars by everyone else in the network.
People are bombarded by information and appeals every day, especially in our newly mobile and tech-centered society, so the effect of any one appeal to do a good deed may get lost. But don’t underestimate the effect of a broadcasting strategy. Our research on get-out-the-vote appeals suggests that the indirect effect of a message on a person’s friends is about three times larger than the direct effect on the person who received the message in the first place. The more you can get people to deliver the message naturally, the greater this multiplier effect will be.
When we studied behaviors like obesity, smoking, and drinking, we found that spouses, siblings, and friends had an effect on each other’s behavior, but next door neighbors did not. So any attempt to change people’s behavior should probably focus on motivating these "strong ties" rather than broadcasting to a wide range of weak connections.
Although most relationships online are not strong (the average person on Facebook has 150 "friends"), we do tend to be connected to our closest friends online too. Therefore, it is possible to use online social networks to reach our real world friends to spread social good. If someone is suggesting friends to a person who could help spread the world, it is important to try to figure out which of his/her relationships are also likely face-to-face. We have done this using photo tags and frequency of communication online, both of which work relatively well.
An experimental study of donations to an NPR pledge drive showed that people donate more when the caller was told about someone else’s donation.
That same study found that when callers heard about an extremely large donation, they opted not to donate at all themselves because they did not want to look "cheap." There is a sweet spot—too low, and it will drag down the average donation, too high and people will not donate at all. In that study they found that the message to optimize donations was one that revealed a donation size at the 90th percentile, in other words, a donation that was bigger than about 90 percent of all donations, but smaller than the other ten percent.
A natural implication of network science is that people with more friends and friends of friends are important because they are more "central" (a smaller number of steps from everyone else in the network). But, as we argue here (PDF), to maximize contagion, they must be 1) interested in spreading social good, 2) influential, and can persuade others, and 3) influence-able by their friends (they are persuadable). Without these other characteristics, even the most connected person won’t be of any help.
In our 2011 flu study (PDF) we showed that people with more friends tend to be affected by things spreading through the network before other people (on average, they got the flu two weeks earlier than others). This means that central actors can also be used as bellwethers to monitor the progress of a social good campaign.
Everything we do ripples through our network. If you feel better because you did a good deed, this will have a positive effect on your friends, your friends’ friends, and even your friends’ friends’ friends. Your own positive change can affect hundreds of people. And who wouldn’t want to make his/her corner of the vast human social network a better place?