You'll see lots of tips and tricks this week for getting the best deals on Black Friday. This is a different kind of list -- the tricks to watch out for. Retailers have an arsenal of evidence-based strategies for making sure you walk out of their stores with far more than you intended to buy. Whenever you start your holiday shopping, see if you can spot these strategies. It's up to you whether you want to fall for them!

1. An inflated "suggested list price" clearly labeled next to the store's discounted price. Neuroscientists know that nothing lights up the brain's reward center faster than a bargain. (OK, maybe cocaine, but let's not quibble.) Discount stores show you the high "suggested price" so that when you see the real price, you'll automatically calculate how much money you're saving. Normally when you consider buying something, the brain registers a kind of pain response at the thought of spending money. But with these sneaky price labels, the brain feels the bliss of saving $40, not the pain of parting with $19.99.

2. Take a deep breath. What's that you smell? Scents to put you in the mood for shopping, wafting at you from carefully hidden scent delivery systems. Retailers know that a tempting smell can be the fastest way to a shopper's wallet, and studies confirm that people spend more when the scent of a store triggers positive associations. Scent marketers take advantage of this by creating unique scent profiles designed to appeal to a store's typical customer, like this profile created by Scent Air for Bloomingdales: "The soft scent of Baby Powder speaks to a mother's memory in the infant department. The intimate apparel department is inviting with the soothing scent of Lilac, while Coconut wafts through the swimsuit department. And during the holiday shopping season the scents of Sugar Cookie, Chocolate and Evergreen create a warm and pleasant experience."

3. Food sales in stores that specialize in non-food products. More and more superstores are adding fast-food restaurants and snack bars. The goal isn't just to turn a profit on cinnamon buns and popcorn, or to keep you fueled for shopping. They're betting that the sight and smell of these treats will make everything-even wire-mesh trash cans-more tempting. And they have good reason to believe this: studies show that high-fat, high-sugar foods shift the brain into a state that makes you more likely to take financial risks and seek instant gratification. It doesn't matter if you indulge or not -- in fact, if you resist the snacks, you may have less willpower to resist the sales.

4. Time pressure. By putting a deadline on the best deals (think 4-6 AM specials), stores create a sense of urgency. You'll be less likely to think twice about a purchase and more likely to throw questionable buys into your cart. It also helps retailers pack the aisles with a little competition for the best deals. We are, in our evolutionary hearts, still hunters and gatherers. The challenge of beating other shoppers to a bargain can leave us just crazed enough to fill our carts with stuff we don't need -- but certainly don't want to lose out on because another shopper grabbed it first.

5. The give-away. Expect stores to advertise or prominently display an item so deeply discounted, they are probably taking a loss on it. They aren't doing this out of the holiday giving spirit. The trick here is to stun you with a price so low that you won't doubt the value of less steeply discounted items. First impressions carry a lot of weight, and if a store impresses you with the very first bargain you see, you'll trust the prices of other merchandise.

Kelly McGonigal is a psychologist at Stanford University. Her latest book is The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do to Get More of It.

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