The New York Post reported Saturday that the crowds and competition to snag the best deals can bring out the worst in some people.

"There's an energy that builds up. People stimulate each other to keep going. And it's contagious," said New Rochelle, N.Y., psychiatrist Dr. Candida Fink. She said people can lose control of their decision-making process as part of a crowd.

"We have no off buttons as a group," she said. "There's no central brain making these decisions. I suspect that there's not anyone in that crowd who doesn't feel horrible -- as an individual -- about what happened."

Dr. Estyne Del Rio-Diaz, a behavioral psychologist in Manhattan, said she blames brain chemistry for Black Friday mania.

She said in crowds "the dopamines -- which stimulate the pleasure parts (of the brain) -- are harried to such an extent that all people are thinking about is what to grab," she said. "The sale, that's what going on in their minds, strictly the sale. They're not caring about who's on their left or their right."