If there is one list we all strive to be on more than the list at the Fly, it's Santa's nice list. So in the midst of the holiday season, don't forget to be kind to the people around you. If Santa isn't strong enough motivation, try this: studies show that taking moral action can result in increased physical strength and endurance.

As a doctoral student at Harvard, Kurt J. Gray, now an assistant professor of psychology at the University of Maryland, conducted research for an article entitled "Moral Transformation: Good and Evil Turn the Weak Into the Mighty." He found that making moral or immoral choices, as opposed to making morally neutral choices, is associated with increased strength and endurance.

"In that study we wanted to see whether good deeds could make people stronger," Gray said. "It's not only that having self-control helps you do good deeds. Doing good deeds actually gives you self-control or physical tenacity."

In the first study, participants had the option to keep a dollar or donate it to charity. Those who were generous could subsequently hold a weight for longer than those who kept the money.

In a second study, participants wrote stories about taking moral, immoral, or neutral actions while holding a weight. Participants that wrote about moral or immoral actions were able to hold the weight for longer on average.

Gray described one test subject, "a really small vegan girl with no muscle mass," and recalled that she was able to outperform him.

"It really is about the strength of mind," Gray said. "If you want to run the Boston Marathon, run it for charity rather than for yourself. If you want to resist eating the cupcake for lunch, donate your change on the way."

The take away? This is a good study to think about during the holiday season. Be nice. Or not. Just don't be neutral.