New York ? While greed may seem an obvious motive for crowds that stampede retailers in search of bargains at this time of year, experts say fear also plays a significant role.

A fear of being unable to afford gifts — given today’s economic woes — may drive many consumers to shop competitively for bargains at dawn, say local psychologists and sociologists.

Many people abandon their normal behavior when caught up in the urge to snag discounted plasma HDTVs like those on sale Friday at Wal-Mart in Valley Stream, N.Y.

And individual judgment can melt away as people react to being jostled in a crowd, which in turn can shatter individual notions of personal space.

Mary Kirby-Diaz, a sociology professor at Farmingdale State College, said average Americans need a space “bubble” of 27 inches.

“What happens is one’s individual identity becomes erased and you become part of the crowd,” said Danielle Knafo, associate professor of clinical psychology at the C.W. Post Campus of Long Island University in Brookville, N.Y.

Knafo compared the shoppers’ surge that left a man trampled to death at the Valley Stream Wal-Mart on Friday to crowd behavior that has resulted in injuries at rock concerts.

“Judgment, intelligence, different kinds of value, compassion — these things go out the window,” Knafo said. “Fear and passion take over.”

Kirby-Diaz said some people become angered by the frustration of being denied a big sale.

“If there’s desire for something they want very deeply and they don’t think they’re going to get it, there’s anger,” Kirby-Diaz said. “Line-cutting makes people very angry.”