Robert Manning, professor of consumer finance and director of the center for Consumer Financial Services at the Rochester Institute of Technology is perhaps one of the most outspoken and informed observers of financial trends in this country today.

His milestone book, "Credit Card Nation," published in 2000, illuminated just how much credit cards have changed the way we think about and spend money. An avid consumer advocate devoted to helping solve what he sees as the consumer debt crisis, Manning frequently appears before the Senate and House committees offering expert testimony and advice. His next book, "Give Yourself Credit," to be published this spring, will help consumers use credit cards and other debt wisely and responsibly.

You've said in the past that credit cards have fundamentally changed the way Americans think about money. How so?

Credit cards have created a cognitive disconnect between what Americans buy and what they can actually afford. When a purchase isn't cash-based, people don't calculate the real cost -- like how many hours of work did it take to get that? The buy-it-now-and-pay-later mentality makes you feel like you can always afford it.

Try this simple trick if you want to see what I mean. Go to the mall and leave your credit cards in the drawer at home. You'll be surprised how many times you'll reach for something and then think better of it if you have to pay in cash.

Research shows that Americans will buy 15 percent to 25 percent more with a credit card than they will if they shop with cash. Americans now spend 130 percent of their discretionary income on their financial obligations and a huge amount of that is credit card debt. No wonder the Commerce Department just reported a negative 1 percent savings rate for 2006, the lowest level since 1933, during the Great Depression.