Every few weeks a heart-warming tale of regular folks deciding to “pay it forward” makes the news. One driver decides to, say, pay the toll for the next person in line, that person pays for the following driver, and so on. A recent example started on Christmas Eve, when more than 1,000 patrons at a Starbucks in Connecticut agreed, one by one, to pay for the customers behind them. People have engaged in pay-it-forward chains at laundromats, fast food joints and car washes. There's good reason to think that these random acts of kindness might be common; after all, generosity has been shown to make us not only happier but healthier, too.

Yet any one of us who has experienced the kindness of a stranger also knows that people can just as easily behave as jerks. Perhaps a driver cut you off as you were maneuvering into the toll lane, or someone stepped in front of you to order a caramel macchiato. Unfortunately, research by my collaborators and me suggests that we are more likely to pay greed forward than generosity.

Imagine being in the following situation. I tell you that I gave someone $6 and instructed that person to decide how much or little of it to give to you, keeping the rest for himself or herself. I hand you an envelope that contains the amount they gave you. You eagerly open the envelope, shaking it to reveal your bounty, only to find that this other person has left you nothing. Not a cent. Take a moment to think how you'd feel—and what words come to mind to describe the guy who stiffed you.

Now imagine that I then gave you $6 and asked you to give as much as you wanted to a new person and keep the rest. How much would you put in the envelope? With that answer in mind, consider another scenario. What if you had opened the envelope and the previous person had instead been amazingly generous, giving you all $6? Or what if the person had decided on an even split, giving you $3 and saving $3 for themselves—how would that outcome affect your behavior?

My colleagues Kurt Gray of the University of North Carolina at Chapel Hill, Adrian F. Ward of the University of Colorado Boulder and I placed hundreds of people in one of the three scenarios just described—they received either greed, generosity or fairness. The results we gathered were not all heartening. But first I'll share the good news. As we reported in a paper that is forthcoming in 2014, we found that people who were treated fairly were very likely to pay forward fairness. If someone splits $6 evenly with me, I'll split $6 evenly with the next person. People who had received the full $6, however, did not reciprocate with equal generosity: on average, they were willing to pay forward only $3. So regardless of whether we have been treated fairly or generously, we tend to respond by behaving merely equitably.

Now the bad news. The people who had received greed were very likely to pay that greed forward, giving the next person just a little over $1, on average. It seems bad behavior leaves more of an impression on us than good.

Why Pay Anything Forward?
To social scientists, what's most interesting about the phenomenon of paying it forward is that there does not appear to be any good reason to pay anything forward. After all, you have had no prior interactions with the recipient and do not anticipate ever meeting the person. It certainly makes sense to pay people back: if someone gave me $0 and then I got the chance to split $6 with that same person, giving him $0 in return might teach him a lesson to be kinder to me in the future. But visiting the sins of one person on an unsuspecting new individual—as participants did in our research—seems less sensible and less fair.

We had a hunch that people are more likely to pay greed forward because negative emotions tend to exert more influence over us than positive ones. To investigate whether this was the case, we asked a new group of participants to take part in a very similar situation, except instead of splitting money they split a set of tasks that were either enjoyable (making fun word associations) or annoying (circling vowels in dense passages of Italian). An unknown person allotted them either all good tasks, an even split of good and bad ones, or only the onerous deeds. Immediately after receiving their assigned tasks, we gave our participants a survey that assessed their emotional state. Then they were given the opportunity to assign another set of tasks to the next person, along the same lines.

Our results revealed that people pay greed forward as a means of dealing with the negative emotions that being treated badly engender. If I can't pay you back for being a jerk, my only option for feeling better is to be a jerk to someone else.

This isn't to say that people don't pay forward good deeds. As the Starbucks example illustrates, people are capable of generating remarkable chains of kindness, under certain conditions. One such condition is a feeling of “groupiness.” Sociologist Robb Willer of Stanford University and his colleagues Francis J. Flynn and Sonya Zak conducted research on Freecycle, a Web site where people post items—from cheap goods such as office supplies to big-ticket objects, including cars—they wish to either give away or obtain. The key feature of Freecycle is that all items must be given with no compensation and no reciprocity. You can't make money, and you can't give in order to receive. The researchers surveyed 805 Freecycle participants on their use of the service. The respondents also answered several questions that assessed how intensely they identified with the Freecycle community. Their results showed that the people who felt a stronger sense of solidarity with the community were more likely to make contributions to the Freecycle network. When users viewed themselves as members of a group of people who help one another, this sense of identity influenced their behavior.

In everyday life, though, many of our interactions are with people with whom we share no group affiliation. In these cases, unfortunately, we should expect to see more greed paid forward than generosity. As a result, we should think carefully about how we choose to react when others treat us badly, lest we become the next link in a perpetual chain of negativity. Luckily, our research offers a way out. We found that having people focus on something positive, such as funny cartoons, can alleviate a greed-induced bad mood and encourage them to end greed chains.

So the next time someone cuts you off in traffic, try blasting a favorite song and singing along. It just might encourage you to be the generous soul who stops the spread of greed.