Many people disengage from charity acts when the social problem seems too big to handle, said Huettel.
"When there's just one situation and one person to help, there are more tangible consequences to the giving," he said.
For years, researchers looked at the theories of reward and personalized charity independently, but now labs are looking at how the two theories work together. But, Heuttel said, there's no science to explaining why some choose to help complete strangers over people they already know.
"It's not explainable in direct order," said Huettel. "At the end of the day you don't get anything out of it but feeling good by helping others."
But perhaps for some, including the "layaway angels," the act of service generates a tangible feeling that can't be replaced.
"I think people really want to help each other this year," said Bianchi. "And we feel absolutely wonderful about it."