You're in the drive-thru line at a fast-food joint hoping to scrape together some sort of snack that will keep the kids from fighting in the back seat as you shuffle them from school to ballet to baseball. You're in a rush. The kids are already snapping at each other — and you're seriously not having a great day. But suddenly, when you get to the window to pay, you learn that the car in front of you has paid for your food. The generosity of a stranger lifts your mood, brings a smile to your face, and leaves you feeling as if the world is just a wonderful place to live. Most importantly, this small act of kindness makes you want to bring these same warm, cozy feelings to others.

Sound familiar? It's happened to me — maybe not this exact scenario, but one very close. And it turns out I'm not alone.

A recent New York Times article told the story of what happened at a coffee shop in Winnipeg, Manitoba, where one customer paid for her order and then picked up the tab for the stranger in the car behind her in line. This one woman's act sparked a chain of generosity that lasted for three hours and the next 226 customers.

Ever since Catherine Ryan Hyde’s 1999 novel, "Pay It Forward," became a bestseller and later a movie, these spontaneous random acts of kindness, have become a common social occurrence. Rather than simply being generous, Americans are opting to help someone from whom they don't expect reciprocation. And in turn, they are spreading good deeds around the world.

Research backs up this phenomenon. In a study published in the proceedings of the National Academy of Sciences, researchers at the University of California, San Diego and Harvard University found that when one person gave money in a "public-goods game" to help others, the recipients were more likely to give money away in the future. The chain reaction continued to build as more people were swept up in the wave of generosity. James Fowler, an associate professor of political science at UC San Diego, noted how once you are the recipient of kindness, "You don't go back to being your 'old selfish self.'"

Turns out, kindness is contagious. Why not start a chain reaction today?

Pay it forward: Good deeds are contagious
Research finds that recipients of kindness are more likely to spread kindness themselves.