The Science of ‘Paying It Forward’

ONE morning in December of 2012, at the drive-through window of a Tim Hortons coffee shop in Winnipeg, Manitoba, a customer paid for her order and then picked up the tab for the stranger in the car behind her in line. Then that customer paid the bill for the following customer in line — and so on, for the next 226 customers, in a three-hour sequence of spontaneous generosity.

It turns out that such “pay it forward” chains are not unheard-of at Tim Hortons (though they are usually much shorter), and news outlets have reported the emergence of many such chains in a variety of restaurant drive-throughs and tollbooths throughout North America. Last year, a Chick-fil-A in Houston experienced a 67-car chain. A few months later, a Heav’nly Donuts in Amesbury, Mass., had a run of 55 cars.

Why do these things happen? One possibility is that generosity among strangers can be socially contagious.
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In an experiment the results of which were published last month in the journal PLoS One, we studied both possibilities. We found that receiving and observing generosity can both significantly increase your likelihood of being generous toward a stranger, but that if you observe a high enough level of generosity, your willingness to help suffers — you become a “bystander” who feels that help is no longer needed.

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