I was walking back to our apartment in Manhattan, the hood of my jacket pulled tight to keep the rain out, when I saw an older man with a walker struggle to descend the slippery stairs of his building. When he almost fell, I and several others went over to help.

There was an Access-A-Ride van (a Metropolitan Transit Authority vehicle for people with disabilities) waiting for him. The driver was inside, warm and dry, as he watched us straining to help his passenger cross the sidewalk in the pouring rain.

Then he opened the window and yelled over the sound of the rain coming down, “He might not be able to make it today.”

“Hold on,” we yelled (there were five of us now) as we helped the man move around the back of the van, “he can make it.”

Traffic on 84th street had stopped. We caught the man from falling a few times, hoisted him back up, and finally got him to the van door, which the driver then opened from the inside to reveal a set of stairs. The man with the walker would never make it.

“What about your side door, the one with the electric lift?” I asked.

“Oh yeah,” the driver answered, “hold on.” He put his coat over his head, came out in the rain with the rest of us, and operated the lift.

Once the man with the walker was in safely, we all began to move away when the driver opened the window one more time and yelled, “Thanks for your help.”

So, here’s my question: Why will five strangers volunteer to help a man they don’t know in the pouring rain — and think about the electric lift themselves — while the paid driver sat inside and waited?

Perhaps the driver is simply a jerk? Perhaps. But I don’t think so. Once we suggested the lift, he didn’t resist or complain, he came outside and did it immediately. And he wasn’t obnoxious either. When he thanked us for our help, he seemed sincere.

Maybe it’s because the driver is not permitted to leave the vehicle? I checked the MTA website to see if there was policy against drivers assisting passengers. On the contrary, it states “As long as the driver doesn’t lose sight of the vehicle and is not more than 100 feet away from it, the driver can assist you to and from the vehicle, help you up or down the curb or one step and assist you in boarding the vehicle.”

So why didn’t the driver help? Part of the answer is probably that for him, an old man struggling with a walker isn’t a one-time thing, it’s every day every stop, and the sight doesn’t compel him to act.

But that answer isn’t good enough. After all, it’s his job to help. That’s when it suddenly hit me: The reason the driver didn’t help might be precisely because he was paid to.

Dan Ariely, a professor at Duke University, and James Heyman, a professor at the University of St. Thomas, explored this idea. They set up a computer with a circle on the left side of the screen and a square on the right side, and asked participants to use the mouse to drag the circle into the square. Once they did, a new circle appeared on the left. The task was to drag as many circles as they could within five minutes.

Some participants received five dollars, some fifty cents, and some were asked to do it as a favor. How hard did each group work? The five dollar group dragged, on average, 159 circles. The fifty cents group dragged 101 circles. And the group that was paid nothing but asked to do it as a favor? They dragged 168 circles.

Another example: The AARP asked some lawyers if they would reduce their fee to $30 an hour to help needy retirees. The lawyers’ answer was no. Then AARP had a counterintuitive brainstorm: they asked the lawyers if they would do it for free. The answer was overwhelmingly yes.

Because when we consider whether to do something, we subconsciously ask ourselves a simple question: “Am I the kind of person who . . ?” And money changes the question. When the lawyers were offered $30 an hour their question was “Am I the kind of person who works for $30 an hour?” The answer was clearly no. But when they were asked to do it as a favor? Their new question was “Am I the kind of person who helps people in need?” And then their answer was yes.

So what does this mean? Should we stop paying people? That wouldn’t work for most people. No, we need to pay people a fair amount, so they don’t say to themselves, “I’m not getting paid enough to . . .”

Then we need to tap into their deeper motivation. Ask them: Why are you doing this work? What moves you about it? What gives you the satisfaction of a job well done? What makes you feel good about yourself?

People tend to think of themselves as stories. When you interact with someone, you’re playing a role in her story. And whatever you do, or whatever she does, or whatever you want her to do, needs to fit into that story in some satisfying way.

When you want something from someone, ask yourself what story that person is trying to tell about himself, and then make sure that your role and actions are enhancing that story in the right way.

We can stoke another person’s internal motivation not with more money, but by understanding, and supporting, his story. “Hey,” the driver’s boss could say, “I know you don’t have to get out of the van to help people, but the fact that you do — and in the rain — that’s a great thing. And it tells me something about you. And I appreciate it and I know that man with the walker does too.” Which reinforces the driver’s self-concept — his story — that he’s the kind of guy who gets out, in the rain, to help a passenger in need.

Ultimately someone else’s internal motivation is, well, her internal issue. But there are things we can do that will either discourage or augment her internal drive. And sometimes it’s as simple as what we notice.

It’s not lost on me that I too have a story about myself — I’m the kind of guy who stops on a rainy day to help an old disabled man to his van — and that it makes me feel good to tell you about it too. That will make it more likely that I’ll do it again in the future.

As we left the scene, I looked at the drivers of the cars who waited so patiently and waved, mouthing the words “thank you” as they passed. Every single one of them smiled back. Wow. New York City drivers smiling after being stuck in traffic for ten minutes? That’s right.

“Yeah,” they were thinking behind their smiles, “I’m the kind of driver who waits patiently while people less fortunate than me struggle.”

Editor’s note: For recent studies on motivation, look at Teresa M. Amabile and Steven J. Kramer’s “What Really Motivates Workers” in the 2010 HBR List, as well as Daniel Pink’s recent book, Drive, reviewed in our Recommended blog.

