NEW YORK (MONEY Magazine) - Prepare to meet your unconscious mind. It could be the best acquaintance you make this summer.

Why? Because chances are much of your financial behavior is driven by tendencies that you didn't even know you had -- tendencies that are likely costing you money every day and quietly sabotaging your long-term financial goals.

Quiz Take the quiz

You don't believe it? Olivia Mellan, a Washington, D.C. psychotherapist, author and money coach, sees it all the time.

She's counseled investors who jump aboard high-flying stocks just before they plunge and then bail out at the bottom, not realizing that the self-confidence that serves them well in other realms can hurt them in the market. She's worked with patients who scoop up a pair of Manolo Blahniks or go out for an obscenely expensive meal after a bad day, not recognizing the connection between their mood and their spending.

"Every one of us has a personality blind spot when it comes to money," says Mellan. The aim of the MONEY personality test is to obliterate these blind spots.

You've probably taken personality tests before. They're a standard tool of corporate human resources departments, which rely on them to help place people in the right jobs. By some estimates, personality testing is a $400 million business. Only recently, though, has personality research made its way into the world of economics, which had long clung to the academic notion that people make financial decisions on a purely rational basis.

Today the burgeoning field of behavioral economics is confirming that our decisions about money are often driven by psychological factors over which we have little conscious control: learned behavior patterns, perceptual biases and -- most important -- emotions. As a result, we're prone to mistakes that undermine our long-term interests.

What personality testing brings to this field is the promise of helping us recognize which errors we're most likely to make -- and to use that knowledge to prevent them. Meir Statman, a highly respected behavioral finance expert at Santa Clara University, teamed with Vincent Wood, president of AdvisorTeam.com, a behavioral research and testing firm in San Francisco, to design the following test.

It builds upon a tried-and-true personality profiling system called the Keirsey Temperament Sorter, as well as a series of studies that Statman and Woods used to isolate the characteristics of each personality type.

Four categories emerged: Guardians, who tend to be cautious with their money; Artisans, who are freewheeling and daring; Idealists, who care less about money than other goals; and Rationals, who make most decisions by the numbers.

Most of us, of course, are a mixture of these tendencies. Still, Statman and Woods' research shows that most of us will find a strong affinity with one or at most two of the categories.

After the quiz, you'll learn how to use your new-found self-knowledge to defend against your weaknesses and take advantage of your strengths.

"If you understand your temperament, you can better manage financial risk and plan your goals," says Statman, "and perhaps become more successful in other walks of life as well."