Supermarkets have our number. They've researched and tracked our behavior - from how we move through the store - to where our eyes land on displays.

Here's what they know about human behavior - so you can avoid being taken in by the tactics that get us to spend more than we should:

  • First, stores know that we naturally move through the store counterclockwise. That's why stores that have entrances on the right do better than stores with entrances on the left. Supermarkets have also engineered the layout so you'll need to trek through the entire store to get what you need. Produce is on the opposite end from the meat, the bakery is far away from the cleaning products. But shoppers are getting wise, The Wharton School of Business put trackers on grocery carts, and found that people are now sticking to the outer perimeter of the store. When you do that, you not only save money - you eat healthier, because all the fresh food is around the edges.

  • The problem is, if you need paper towels or deodorant, you've gotta go into the middle aisles - and that's where they'll get you. The inner aisles are primarily junk food, processed food, higher-margin items, and things we really don't need. And the shelves are orchestrated to get us to spend more. Pricier, brand-name items tend to be at eye level, while the less expensive, generic ones may be on the bottom shelf. That's because companies pay a premium to be placed at eye level - where we naturally look. It's called a "slotting fee" - and brands will spend $30,000 a year to get good shelf placement in just one city, in one grocery store chain. So, to save money - reach for the bottom shelf, where items may be up to 50-percent cheaper than on higher shelves.

  • The final money-saving tip: Grocery store scanners are wrong on 3 items in 100. Shoppers lose nearly $3 billion dollars a year on scanner errors in the U.S. alone. So, pay attention to the scanner prices, and check your receipt.