Make your post-Thanksgiving food coma work for you: New research suggests that eating a big turkey dinner may keep you from spending impulsively on holiday sales.

The study, published in the December issue of the Journal of Marketing, builds on the turkey-tryptophan trope that we all hear this time of year -- it's practically guaranteed that somebody at your Thanksgiving gathering will say,"Did you guys know that turkey makes you sleepy?" That's only kind of true -- an amino acid called tryptophan is found in turkey, and it does work as a natural sedative, but we really don't eat enough of it, even at Thanksgiving, to be affected. Our after-dinner lethargy is more likely caused by overindulging on delicious carbs and cocktails.

But the body uses tryptophan to produce serotonin, and serotonin is known to inhibit impulsive behavior, which made researchers from the University of Utah curious: How might Thanksgiving dinner affect Black Friday binge buying?

To find out, they recruited 170 volunteers and instructed them to fill out an online survey on Thanksgiving evening in 2007. They rated how likely they were to buy popular items at a deep discount -- such as a Dell laptop marked down to $499. Those who had consumed a traditional Thanksgiving dinner were less likely to splurge on any of the marked-down items, say Arul Mishra and Himanshu Mishra, the University of Utah marketing professors that co-authored the study. (Fun fact: They're also husband and wife.)

Of course, as Himanshu Mishra points out, "The influences are not going to be there after 12 hours. If someone is going out shopping tomorrow morning, probably the person will not see that effect." So here's how to make these new findings work for your wallet: Either skip the shopping on Friday and do your holiday shopping online Thursday night, or load up on leftovers before heading out to the stores on Friday.

Would you give this a try? Or is impulse shopping on Black Friday half the fun?

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If you feel a little snobbier when behind the wheel of a BMW, or a little more outdoorsy when you slip on a North Face fleece, or a little hipper when using your new MacBook Air -- you're not alone, as they say. It's widely known that a product's brand image has a profound impact on our own self-image, but a new study finds that we may actually change our personality to match the "personality" of a brand.

"For example, if I want to convey an image of being adventurous, I might buy a Harley-Davidson motorcycle or wear casual clothes from outdoor adventure companies such as REI," says Deborah Roedder John, a marketing professor at the University of Minnesota and one of the authors of the study published in the December issue of the Journal of Consumer Research. (You can find the report here, but a subscription is required.)

John continues, "But our prior research didn't delve into the question of whether consumers actually 'took on' the personalities of these brands they selected to boost their self-images: If you buy a Harley motorcycle, will you really see yourself as more adventurous?"

For one part of the study, the University of Minnesota researchers recruited about 100 volunteers -- all women, all between the ages of 18 to 34 -- at a mall, asking each of them to carry around for an hour the shopping bag of their choice: a bag from Victoria's Secret, Old Navy or Limited Too. Every participant chose the pink Victoria's Secret bag. When they came back from an hour of shopping, Victoria's Secret shopping bag in tow, they were asked to take a survey rating how they felt about themselves. The researchers found that the "personality" of Victoria's Secret -- sexy, glamorous, feminine -- actually did make some of their volunteers feel sexier, more glamorous and more feminine. (No word on whether carrying around a bag from Victoria's Secret made some feel a little like a 15-year-old.)

The same researchers did a similar experiment instructing participants to write with a pen with an MIT logo on it, with similar results -- some of the participants really did feel smarter when using their MIT pen. (The researchers conducted four separate studies, involving more than 200 participants in all, John says.)

The trick is this: If you're the kind of person who thinks a particular brand will make you more feminine, or more glamorous, then it will. That's called "entity theory," and it means you're the kind of person who seeks out products to make you feel a certain way about yourself. But if you're not the kind of person who feels that way about the brands you buy, well -- then you won't feel much of anything after using a particular brand. That one's called "incremental theory." You might think you're staunchly one way or the other, but these researchers primed their participants to identify with one of those theories by having them read an article promoting it.

The study results shed light on how those "entity theorists" and "incremental theorists" experience brands differently. An entity theorist is -- well, let's just let the experts explain it, as John and her colleague Ji Kyung Park write in the report:

Individuals who endorse entity theory view their personal qualities as something they cannot improve through their own direct efforts; instead, they seek out opportunities (such as brand experiences) to signal their positive qualities to the self or others. Conversely, individuals who endorse incremental theory view their personal qualities as something they can enhance through their own efforts at self‐improvement, reducing the value of signaling opportunities through brands.

"For consumers, our study could help them understand how brands really affect them -- just carrying a shopping bag with the Victoria's Secret name makes you feel more glamorous, feminine, and good-looking (at least for a good deal of people we call 'entity theorists')," John says. "So, you don't really need to buy and use the brand--just have some association with it. Maybe this is a money-saving tip for anyone strapped for money during these recessionary times?"

What do you think? How does the stuff you buy influence the way you feel about yourself -- or does it at all?

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