We’ve all been there. A quick trip to the grocery store for essentials turns into an over-flowing shopping cart. But what makes us purchase so much when we had planned to purchase so little? One thing that might be contributing to our over-purchasing is that shiny shopping cart.

Simply offering consumers the ability to use a cart increases the chance a consumer will purchase more, at least that was the thought behind the cart’s creation in 1938. The first carts were composed of two stacked wire baskets. The carts we use today have nearly tripled in size from their humble beginnings, Slate reports.

Now we have wide, open-space carts at nearly every supermarket and grocery store, not to mention the flatbed-like carts employed for easy transport of bulk items at stores like Costco or Sam’s Club.

So, are carts truly the reason we’re spending more at the grocery store? Marketing consultants say the ever-increasing size of carts certainly doesn’t help control purchases.

An experiment found that when the shopping cart was doubled in size consumers went on to buy 40% more, says Martin Lindstrom, a marketing consultant and author of Brandwashed, told TODAY.

It’s not just traditional supermarkets that are increasing sales with bigger cart sizes. Lindstrom notes that Whole Foods’ shopping carts nearly doubled in size from 2009 to 2011.

Even shopping cart manufacturers tout the power of cart size in increasing sales. Americana Companies, a Shenandoah, Iowa-based company, highlights the double basket cart as a “new way to increase your bottom line with more sales”.

When the “hand basket is full customers will check out,” and if there is a double basket cart you can “double your sales.”

If a big shopping cart means you’ll buy more, then a shopping basket means you’ll purchase less, right? That’s not always the case.

Sure, you can fit a lot less in your basket, but the types of foods consumers purchase are markedly different and not in a good way.

The Journal of Marketing Research found that consumers using a shopping basket were more likely to purchase unhealthy, wasteful items.

But those purchases have less to do with the size of the basket and more to do with the sensation of holding the basket. The sensation of flexing arm muscles to hold the basket creates a feeling of instant gratification, making consumers more likely to buy items that offer the same sensation, like a candy bar, researchers found.

Of course we can’t blame our high shopping bill on just the cart, there are other things we’re doing that don’t help our wallets. To avoid over-purchasing at the store make sure you bring a list, never shop hungry and follow these tips.

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