(MONEY Magazine) – You may think of yourself as the most savvy of consumers, immune to the siren songs of advertisements, able to turn a blind eye to the Internet pop-ups that seem to know what you're thinking. Not even the flattery of a consummate sales pro can work its magic on you.

So why is it that you spend 146 hours a year shopping? Yes, that's right. Including time spent in stores, reading catalogues, watching shopping shows on TV and surfing the Net, Americans spend an average of 146 hours a year searching for things to buy, according to the Bureau of Labor Statistics. That's more time than we spend reading or cleaning the house and the same amount as we spend cooking.

We're losing the battle against marketers intent on getting us to spend more than we have on things we don't need. A recent survey of 700 MONEY readers found that more than half had, in the previous six months, made a major purchase they regretted. How are you and so many other smart consumers being reeled in? Science and money. Market researchers working for retailers and consumer-products makers are trying to learn everything about you. They fund academic research that delves into every facet of consumer psychology and behavior. They spend $5.6 billion a year hiring consultants, conducting focus groups and testing, testing, testing to figure out how to make their product seem to be the very best way to scratch your particular itch. What chance have you got against all that firepower?

A pretty good one, actually. You can stop yourself and your kids from taking the bait. Our survey identified the five most common reasons MONEY readers give for making a purchase. We then asked top psychologists and marketing experts to help us develop strategies that will help you challenge those rationales. For starters, check "Before You Buy, Ask" below. Then read on and learn what you can do to emerge from the mall knowing yours was money well (and intentionally) spent.

Rationale 1 IT LOOKED GOOD AT THE TIME Two-thirds of all purchases are unplanned buys, says Paco Underhill, a marketing expert and author of Call of the Mall. Crafty retailers have figured out how to translate your fleeting desires into piles of cash. With the help of focus groups and "retail anthropologists" like Underhill watching thousands of hours of people in stores, they know more about how we shop than we do. They know, for example, that bright red typically is a better attention-getter than bright blue (from Coke cans to the McDonald's logo to the Levi's tag on your jeans, most category killers have at least a dash of red). They arrange aisle shelves and traffic flow so that pricier items are within grabbing distance of your right hand because they know that 85% of us are righthanded. They know that when you're buying Diet Pepsi, you'll grab and go, but if you're considering a cashmere sweater, you need to be able to inspect it without other customers invading your space.

HOW TO RESIST

• "You're far more likely to lose the battle between desire and willpower when your self-regulatory resources are depleted," says Ron Faber, a professor at the University of Minnesota who studies consumer behavior. So don't hit the stores or your favorite shopping website when you're tired, or after you've had a glass of wine, a fight with your spouse or a lousy day at work.

• Avoid environments that really get you going. If you have trouble resisting in malls, pick out a single store in a location away from a mall. If catalogues are your downfall, get yourself off the mailing lists. Love home-shopping TV networks a little too much? Ask your cable company to block the channels.

Rationale 2 I'VE EARNED IT You lost those last 10 pounds, made it through a week without a cigarette, blasted the competition in the month's sales tallies. Of course you deserve a reward—and you're just the person to give it to you. Academics call this self-gifting. And marketers love it. That's because, as Faber explains, when we buy gifts for ourselves, we tend to spend more than we would if we were buying for someone else, and we justify the purchase as something we've denied ourselves in the past.

For Ken Lubker, that reward was golf clubs. Lubker, the sales manager for a television station in Columbus, Ohio, rented a set of oversize Titleist 822s during a business trip to Bermuda last summer. "I played unlike myself," says Lubker, 43. His chronic slice just disappeared. "I knew it couldn't have been me. It must have been the clubs." And when he got back to Columbus, he couldn't stop talking about them. Finally, his wife Jean, 44, who was getting awfully tired of hearing about these magic wands, said to him: "Oh, just buy them! Consider it a reward for all the work you did on the trip." So he did.

"Marketers spell out the reward pitch loud and clear," says Helen Woodruffe-Burton, a professor at the University of Lancaster in the U.K. "They want you to think it's okay to give yourself a pat on the back. You've earned it, they want you to know. Besides, no one else can be counted on to give it to you." That's a line often directed at women. Witness the right-hand ring campaign launched in 2003 by a division of De Beers, the world's largest diamond miner. The slogans include the hit-you-on-the-head "Your left hand says 'we'; your right hand says 'me.'" The pitch says it doesn't matter if you're one of the growing number of women who are single or divorced, explains Mary Lou Quinlan, a marketing consultant and author of Just Ask a Woman. "They say you deserve a gorgeous thing just because you're you." The campaign has given the diamond industry a way to unload its excess inventory of small stones.

• To quell the urge to spend your money today, think about the bigger reward out there for you in the future. A second home? A trip to Europe? The feeling of relief that comes with making yourself debt-free? Take the money you were about to plunk down, and put it toward that bigger reward. Chart your progress, so you get some immediate gratification.

• Think about a less expensive alternative. That's exactly what Ken Lubker did. Instead of blowing $800 on a brand-new set of golf clubs, he spent $300 on a used set. And he's still playing great.

Rationale 3 IT'S JUST A HABIT Women make more purchases than men do, but when it comes to habitual buying—patronizing particular stores or shopping sites on such a regular basis that you buy without thinking—guys do more of it. So do shoppers of either gender who earn more than $100,000 a year.

The Internet, of course, is tailor-made for habitual shoppers. It's open 24/7, so you can always satisfy your shopping jones, and merchants are happy to send you daily e-mails reminding you to come back. Some, like Bluefly, featured a different sale item every day during the holiday period. Others, like eBay, change their home pages so they always have something new to show you. The Web has Queens, N.Y. retiree Phillip Vili, 75, hooked. "Mostly I buy jewelry for my wife," he says. "She needs more jewelry like she needs a hole in the head." So why does he do it? "It's fun," he says. "Besides, I've been doing it for so long, it's part of my routine."

Marketers know how to make your routine feel rewarding, through frequent buyer discounts or in more subtle ways. At Firehook Bakery, a popular chain of coffee bars in Washington, D.C., staffers learn the orders of repeat customers so that they can tell you what you want before you open your mouth. "The act of buying a $3 cup of coffee becomes the satisfaction you get from feeling like a regular," says Seth Godin, author of Free Prize Inside, a book on marketing.

• There's a chain of events that generally leads you to buy. Break it. If you run through a list of shopping sites every day, remove them from your Web browser's "Favorites" list. If you always stop in the music store as you walk from your office to your car, stay at work for another 15 minutes so that you don't have time to shop. Or park in a different lot and avoid the store.

• Still craving routine? Devise a cheaper one. Stop at the office coffeemaker and pour a cup to have with the breakfast bar you brought from home.

Rationale 4 IT'S A SOCIAL THING Bruce and Melissa Pecci have three kids under the age of six. When the Westerville, Ohio couple manage to hire a babysitter for an evening out, the thing they crave most of all is adult conversation. That makes dinner and a night at Restoration Hardware or Crate & Barrel much better than a movie. "We've been building a new home," explains Melissa. "Walking through a furniture store, we can imagine what our lives would be like if we bought this entertainment center or that bedroom set. It's a way for us to dream."

Men don't shop together much. And if and when the Y-chromosomed discuss their purchases, the banter tends toward the competitive (as in my plasma TV is bigger than yours). For women, though, shopping is a social event. In part, that's because they've been trained to think like this for generations. Until early in the 20th century, stores were among the few places women could go unaccompanied by men without risking their reputations. As a result, Woodruffe-Burton explains, department stores evolved as "pleasure palaces" designed with women in mind. Today women still do 80% of all the buying in this country. And it's the buying that makes the bonding experience of shopping complete, says Quinlan. When your friend comes to your house and sees the leather recliner she helped you pick out, you both can feel good about being a helpful presence in each other's lives. Unless, of course, you really shouldn't have spent the money in the first place.

• Your best friends should be able to help you save money as well as spend it. So if the goal is new towels for the guest room without busting the budget, tell your friends before you hit the stores. That way they won't try to convince you to buy $65 Turkish bath sheets.

• If, like the Peccis, your shopping partner is your spouse, resisting should be even easier. You're both trying to save for that new house or new car, you're both trying to get rid of the balance on the Visa card. You can remind each other of those goals as you salivate over the latest in cell phones or coffee tables.

• Well, you could do other things besides shop, right? You needn't go cold turkey, but cut the number of trips in half. The treasure hunts you do go on may be that much more rewarding.

Rationale 5 I FEEL BETTER WHEN I DO You've heard of retail therapy. The academic term is compensatory consumption. You buy to make up for some other deficiency in your life. People shop to fill the gap between who they are and who they want to be, explains Woodruffe-Burton. "They figure, 'If I buy this Chanel suit that I associate with being up to the minute, I'm going to feel up to the minute too." It's not that buyers truly believe owning a single Chanel will launch them into the pages of Vogue. They're just looking to be the head turners in their own little world.

In extreme cases, the attempt to fill a void leads to compulsion. Jean Smith, 58, of Grand Rapids, started shopping after her youngest child left home. At first she shopped occasionally, but she got such a thrill that she quickened her pace, ramping up to every other day. "If I didn't go to a mall on a weekend," she says, "I felt like I had to go on a Monday." Her obsession: pricey purses. She accumulated five, then 10, then 30—some costing more than $500. There were three Louis Vuitton. Three or four Coach. A couple of Dooney & Bourke. "I became like Noah with the ark," she recalls. "It wasn't enough to have one of something. I always had to have at least a couple." And where are those purchases? As is typical, many are in a closet, still in their bags.

After her husband retired and the couple's income declined, Smith, who owns a cleaning service, cut back. "There may be a day when I'm not able to shop much at all," she says. "I don't know how I'll deal with that."

• If your impulses are truly out of control, you may need professional help. Antidepressants are used to treat shopping disorders, and there are support groups like Debtors Anonymous.

• For most of us, knowing what drives our need to buy may help us stop our shopping, says Lars Perner, a professor at San Diego State University. Consider this: Do the fawning clerks at your favorite stores make up for a lack of attention from someone else? Do you feel smart when you find a bargain and not so smart on the job?

• Go back to the first page of this article and cut out the six-question card designed by New York psychologist April Benson, founder of Stoppingovershopping.com. It will push you to ask why you're really about to make a purchase. Tape it to your credit card. You'll buy less, and like what you do buy more.