For many bargain-hunting Americans, the day after Thanksgiving is perhaps one of the most important holidays of the year — even though Black Friday is not officially recognized on any calendar. The opportunity to get Christmas shopping done at a discount is just too much temptation for the many shoppers who might otherwise be spending the wee hours of that Friday sleeping off a tryptophan-and-pumpkin-pie hangover.

But Black Friday isn’t just about bargains and deals. Often shoppers will find themselves spending more than they intended on items they don’t really want. In addition, otherwise civil individuals may find themselves pushing and shoving fellow shoppers over coveted merchandise. And in the worst cases, shoppers and employees have been hurt and even killed in stampedes to get to cheap video game consoles and laptops. These are not the actions of rational individuals.

As easy as it might be to simply look down our noses at those involved in the most egregious excesses of Black Friday, the sad truth is that human psychology primes all of us to potentially act in the same way. And of course, retailers are savvy enough to recognize our baser impulses and take advantage of them. Here are the five psychological quirks that retailers exploit and we blindly follow on Black Friday, often to the detriment of our wallets, our dignity, and potentially our very hides. (See also: Party Like It's 19.99: The Psychology of Pricing)

1. Time Pressure Makes Us Act Without Thinking

Even if you generally take your time to research and think about big purchases, the idea that a sale is for a limited time can make you forget your usual deliberate approach.

For example, you might be thinking about buying yourself a flat screen TV, but you would like to do some research and comparison shopping. If you happen to be in a store with an incredible one-day sale on their flat screen TVs, your plans to research your purchase are likely to go out the window. You would hate to miss out on big savings because you were being too deliberate, wouldn’t you?

Art Markman of Psychology Today explains that when stores offer the time pressure of Black Friday only sales (or sales only within a certain window on Black Friday), it affects what psychologists Arie Kruglanski and Donna Webster have called a "need for closure." This concept refers to an individual’s need to finish with a decision process and subsequently take action. Some people have a high need for closure, meaning they want to make their decision quickly and move on, while those with a low need for closure are more comfortable thinking carefully through each decision before taking action.

What happens when retailers put a time limit on their bargains is that it raises the need for closure, even for normally low-need-for-closure shoppers. Since the retailer has created a sense of urgency for the shoppers to take advantage of a good price, those shoppers are less likely to spend time carefully thinking through their purchases.

And this is why you may find yourself wondering why on Earth you put five crock pots in your cart on Black Friday when no one on your Christmas list cooks. You are reacting to the low price and urgent time limit rather than taking the time to think about whether this is a good purchase.

2. Doorbusters Play on Our Fear of Losing Out

Most chain retail stores will offer an incredible deal on a couple of big-ticket items. The problem with these doorbusters is that the stores generally only have limited quantities in stock — as low as 10 guaranteed units per store. Not only does the advertised item get you up and waiting outside the store with the slavering hordes first thing in the morning, but its very scarcity really primes your competitive instinct. You want to beat out all the other suckers in line.

And if you are one of those suckers who misses out on the doorbuster? Very few people will then head home in a huff after losing out on the advertised sale. If you’ve already dragged your rear end out of bed at 0-dark-30 the day after Thanksgiving, you might as well do some shopping. Your fear that you have gotten up early for nothing can lead you to making purchases you didn’t intend.

In addition, the doorbuster’s incredibly low price might convince you that the rest of the merchandise at the store is also on sale, even if you don’t have any idea if that’s true.

3. Competition for Merchandise Makes Us Enjoy the Hunt Even More

We all get a charge out of saving money. Add in the potential competition of every other early-rising Black Friday shopper, and it turns a mundane activity — shopping — into a pleasurable one.

According to Sang-Eun Byun, assistant professor of consumer affairs at Auburn University, the competition of other shoppers “creates what’s called hedonic shopping value, or a sense of enjoyment from the mere process of buying goods.”

Retailers take advantage of this sense of pleasurable competition by limiting the number of doorbusters and loss leaders and by adding time pressure. They create a sense of implied scarcity by imposing these limits, which engages our hoarding and hunting instincts.

Shoppers can take great pleasure in figuring out the best ways to take advantage of retailers’ limits, as it makes them feel superior to other shoppers. Actually buying the sought-after item feels like winning.

Unfortunately, shopping competition can lead to even darker behavior.

4. Planning Your Shopping Strategy Can Make You More Prone to Misbehavior

You might remember the California woman in 2011 who pepper sprayed her fellow Wal-Mart shoppers at the very beginning of Black Friday sales last year. What got less coverage was the fact that this walking affront to Miss Manners turned herself in 24 hours after the pepper-spraying incident. Presumably, she had come to her senses by then.

According to psychologist Jane Boyd Thomas, it’s likely that the pepper-sprayer had planned her shopping strategy and mapped out her route through the store. Thomas’s research into the consumer psychology of Black Friday showed a correlation between those shoppers who strategically planned out their shopping expedition and those who engaged in rowdy behavior.

While most shopping misbehavior is limited to nasty looks, rude hand gestures, and the occasional scuffle over an item, it does not change the fact that normally polite individuals may find themselves acting in ways that would shock their grandmothers on Black Friday. Having a vision of how your bargain-hunting triumph will play out can apparently make you more aggressive when other bargain hunters get in your way. Your dashed hopes for a successful “hunt” can lead to negative behavior.

5. A Store’s Environment Can Put You in a Buying Mood

Retailers recognize that making sure you’re in the right mindset to shop will improve their profit margin. Everything from the crowds to the store décor to the music playing over the loudspeaker to the scent of warm cookies filling the air can help to convince you to stay longer and spend more money. This is particularly true during holiday shopping, as Christmas has a warm-and-fuzzy connotation and mood for most shoppers — and especially those shoppers who are likely to go to the stores on Black Friday.

As Stephanie Pappas reports in LiveScience, studies have shown that “positive feelings make products seem more desirable.” By taking advantage of holiday mood-setters like Christmas carols and decorations, retailers prime their shoppers to feel upbeat and excited for the holiday, which can make them purchase more.

The fact that so many other people are out shopping with you can also make you feel positively about the coming holiday. It positions you as all celebrating the holiday together — even if you are at the moment in competition for specific gifts.

And the psychology of smell is such that a pleasant scent can make you feel great — and spend more. Scent is very closely associated with memory, and smelling tempting aromas that we associate with holidays — like cookies, peppermint, or fir trees — can make us remember happy Christmases past, which can lead to more spending. We want to pass that happiness along to next generation, after all.

Avoiding the Madness

Black Friday has been engineered to play on our spending weaknesses. It often brings out the worst in us, whether that is our competitive nature or our budgeting weakness in the face of $200 laptops. If you plan to partake in Black Friday shopping this year, be intelligent about it.

1. Do Your Research Ahead of Time, so That You Will Not Be Tempted Into a Purchase Just Because of the Sale Price

Remember, you’re not saving money if you wouldn’t have bought the item at full price.

2. Be Willing to Go Home Empty-Handed If the Item You’re Shopping for Is Sold Out

Heading home for a couple extra hours of sleep is a better idea than buying something just to make your trip worthwhile.

3. Enjoy the Shopping, but Don’t Make a Competitive Sport Out of It

Buying something isn’t “winning,” the other shoppers aren’t your opponents, and this is all theoretically being done in order to buy gifts for those you love. So don’t act in a way that would make them ashamed. They’d rather have you come home empty-handed than with a black eye and missing teeth and the cheap video game in hand.

4. Embrace Your Inner Humbug

While it is lovely to enjoy the holiday mood at your favorite retailer, remember that it is being cynically used against you. Keeping that in mind can help you to keep your wallet fat and the questionable purchases to a minimum.

You might want to refrain from saying “Bah!” to anyone who wishes you a Merry Christmas, however.