Whether it's a limited-time offer from a fast-food restaurant, or the hot-selling toy the manufacturer seems to not have made enough of — consumers are driven to buy when a product is scarce — even when it's an artificial scarcity, according to experts.

Santa shines the Neiman Marcus limited edition BMW Individual 7 Series Sedan during the unveiling of the the Neiman Marcus Christmas Book. Consumers are drawn to scarce limited edition products. (Donna McWilliam/Associated Press)The tactic is used so often in North American marketing that you might expect consumers are immune to it.

The Gap sells limited-edition jeans. Artists Robert Bateman is big on limited-edition prints. And in recent months, Frito-Lay has been offering "Cheesy Enchilada" Cheetos with the words "Limited Time Only!" printed on the bag. Could that availability be limited by anything other than their desire to grab our attention?

And yet, rather than ignoring the ads or balking at their false premise, consumers enthusiastically encourage the practice by jumping for limited-edition goodies.

'We move into that hoarding, greedy thing even though we know it's not true.'—Marie Gray, psychologist

How is it that people still get so excited, rather than annoyed, when they're manipulated by the threatened disappearance of something they want?

It's a mix of old instincts and modern challenges, according to psychologist Marie Gray, who teaches at Misericordia University in Dallas, Pa.

"Our nervous systems get activated," she says, "and we move into that hoarding, greedy thing even though we know it's not true."

Disney master of limited time releases

In announcing that the animated film Beauty and the Beast would be available on DVD beginning in October, a Disney website uses the phrase "Finally releasing from the Disney vault for a limited time."

Paris Hilton shows off one of the new watches of her Paris Hilton Limited Edition Watch Collection. Hilton's 18K white gold and diamond encrusted watches start at $100,000. (Stephen Chernin/Associated Press)Fans know the drill: When a movie emerges from the "vault," they whip out their credit cards to grab a copy before the company pulls it from store shelves again. It's received as an opportunity, rather than a marketing gimmick.

"There is an element of appealing to scarcity that always works in every human being," says Jayanthi Rajan, who teaches economics and business at Albright College in Reading, Pa.

Still, North Americans like nothing more than getting what they want when they want it. Will the day ever come when consumers put limits on their tolerance for "limited time only" goods?

Probably not, said Morris Shapero, who teaches and studies marketing and culture at Eckerd College in St. Petersburg, Fla.

"We live in the moment and we're a very futuristic society," he says. "We say, 'Give me what I want and I'll move on to the next thing."'

When it comes to our shopping habits, he says, "We don't hold grudges."