The doughnut shop I pass on my drive to the hospital isn’t the kind of place where you might expect to see outpourings of random kindness. It sits in the shadow of a raised highway, a few doors down from a bail bond business and a block away from a prison complex that resembles a medieval castle.

One Sunday before Valentine’s Day, the line to get served there was long, checkered with homeless people — some of whom sleep under the highway to stay dry and protected from the wind — and more well-off people getting breakfast or bringing bagels or doughnuts to work or church.

A homeless couple stood ahead of me. Their clothes and hair were dirty, and the undersides of their fingernails were caked in dirt, as if they had just come in from gardening without gloves. They appeared very much in love — standing close, gently touching and smiling. She wanted a heart-shaped doughnut, and he wanted the same. They reached deep into every pocket counting their change, hoping to find enough.

They were a nickel short. Sheepishly, they turned to me and asked for help. I had a feeling of injustice: Here I was bringing doughnuts to doctors, nurses and staff who did not need them, yet this couple would not have breakfast without help. Not wanting to shame them, I softly told them that they could order whatever they wanted and that I would be happy to buy them breakfast.

When they ordered, the cashier looked at them judgmentally. Perhaps she had been stiffed before, or maybe she knew they did not have the money. The woman spoke up, stating that I had offered to pay. The cashier looked at me and I nodded.

That is when the cascade started. “What a great idea,” said a woman behind me, who was picking up doughnuts for Sunday school. She offered to buy breakfast for the homeless person next to her. The nurse behind her did the same, as did the police officer further back. The nurse and Sunday school teacher discussed how they were going to come back the following Sunday to do this again.

I was also moved by their generosity and handed the homeless couple more money to cover lunch and dinner and perhaps pay for a stay at a shelter. They wept, and I sat down at the table with them. They spoke excellent English, as if they had graduated college or higher. The man explained how they never intended to be that way. They hit some “rough patches” and made a couple bad decisions, he said. “We are something,” the woman told me. I told them that I believed them. My only request, I said, is that when they got back on their feet, they “pay it forward” to someone in need.

For weeks, I reflected on that day not quite understanding what exactly had happened. Then I read a New York Times article on the science of paying it forward. Cornell University sociologists Milena Tsvetkova and Michael Macy explained how we are much more likely to perform a kind act when we experience or witness one. Experiencing a small kindness is more potent than observing one, though in the case of the doughnut shop, observing proved a potent pill. They describe how chains like I observed are not rare at all. At a drive-through coffee shop in Manitoba, Canada, one customer paid for the person behind them, and the chain progressed to 226 people. At a Chick-fil-A drive-through, there was a 67-customer cascade after one generous customer paid for the person next in line.

Of course, these remarkable phenomena all fit a pattern: Random events that occur as people are waiting in some sort of line. Health care is different, of course. We can’t easily pay the doctor’s bill for the person next to us. But what if we could bottle whatever it is that makes these events happen, and use it to deliver safer, higher quality and more patient-centered care? There is a large segment of health care workers who want to do the right thing, to do things differently, but are held back for a variety of reasons. Sometimes they just want to know that there are others who are willing to move forward with them. Someone needs to takes that first step, to set off the chain reaction. Others want to know that if they lead, others will follow.

Take, as a great example, Janet Wall, a support associate on the Weinberg ICU at the Johns Hopkins Hospital. Wall has worked on the unit for 14 years and often jokes that she is “protecting her house” when she sees a behavior that is not consistent with the values that the unit is built around. If she sees anyone neglect to perform hand hygiene before entering a patient room — be it a world-renowned surgeon or a clerical worker — she will immediately remind them to do so. She’s on the unit to save lives, she proudly announces.

Anyone who has worked in health care or been a patient knows how uncomfortable it can be to ask someone else to wash their hands. But Wall took the risk to do something different and hold others accountable. And once she did, other support associates and staff began to follow. Many staff who had never before taken those kinds of risks began to speak up. This social movement has spread around the unit, and even nurses who before did not feel empowered to speak up are doing just that. Such phenomena take me back to a quote from the famed anthropologist Margaret Mead that has provided inspiration to those of us at the Armstrong Institute for Patient Safety and Quality: “Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it’s the only thing that ever has.”

Acts of leadership and courage can be powerful forces for social change when they are aligned towards a goal. And as Wall demonstrates, you don’t need a C-suite title to set these in motion. So start a social movement in your unit or clinic. Take that first step — an uncommon act of kindness, generosity or courage. Witness or experience these acts, and then pay it forward, and watch as the world around you begins to change.

Peter Pronovost is an anesthesiologist and director, Armstrong Institute for Patient Safety and Quality.  He blogs at Points from Pronovost.