Two people were yelling when I walked into a NYC fast food restaurant. Even though the counter area was packed, the crowd had edged back enough to create an open area around them.

"That's my $5 bill!" one man yelled.

"The hell it is!" the other yelled, grabbing a fistful of shirt and tossing in an Oedipus reference for good measure. 

Just then a security guard pushed his way through the crowd.

"How long had that been going on?" I asked a man beside me.

"Two or three minutes, at least," he said. "Someone should have done something."

Science says that "someone" tends to be someone else, especially when there's a crowd. Research shows we're less likely to take some sort of action when other people are present; in fact, the more people around, the less likely any one person is to step in.

"Diffusion of responsibility" helped cause all the people in the restaurant, including the employees, to wait for someone else to intervene.

Yet based on conversations I overheard, at least a few people were disappointed in themselves for not having tried to defuse the situation. 

Which also makes sense.

Even so, once in a while "someone" does step in.

A few years ago, 19 year-old Dairy Queen employee Joey Prusak was working the counter when he saw a blind man unknowingly drop a $20 bill.

A woman behind him in line picked it up and put it in her purse. Prusak asked her to give the man his money back, but she claimed she had dropped the $20 bill. After a brief argument the woman left the store and the gentleman sat to eat his food.

And a few minutes later, Prusak took a $20 from his pocket and gave it to the man. 

As another customer said, "I was in shock by the generosity that your employee had, taking his own money out of his own wallet to give to the customer because some other lady decided to steal something that wasn't hers."

Prusak stepped in to try to make the situation right. When that didn't work, he went above and beyond.

Did he need to give the man $20 from his own pocket? Of course not. That gift was the icing on a "do the right thing" cake.

What mattered is that Prusak didn't wait for someone else to step in. 

As Nelson Mandela said, "Courage is not the absence of fear, but the triumph over it." 

Think of bravery that way, and courage is often required, especially when other people are involved: Taking a chance when others will not. Or following your vision, no matter where it leads. Or standing for what you believe in, even though those beliefs may be unpopular.

Or doing the right thing, even when doing the right thing may also be the hardest thing.

Because one person's actions can often inspires someone else to step up the next time.

And which makes it more likely that, the next time, that "someone" will be us.