The weekend before Christmas, I was sucked into a giant, enticing vortex of craving and desire, stuck for hours with the inability to leave—my only limitation being my wallet.

In other words, I went to Target.

And—again, in other words—I was like a bull in a China shop.

Back in 2009, Target introduced new gigantic, plastic, Playskool-esque shopping carts. Maneuvering the aisles is like passing a car on a one-lane country road in a Hummer.

Of course they're ridiculously cumbersome, but it's all a trick on the Target executives' part—the bigger your cart, the more you can fit in there. You'll look silly hauling around a couple packages of pens and a box of tissues to the checkout counter, after all. Better head to the appliance section and fill it with a microwave or plasma TV.

In this second installment, we'll explore how stores betray our sense of sight, tricking us to buy stuff we really don't want or need.

Retailers have—quite creepily, actually—studied our every move. In fact, they've found that we like to shop counter-clockwise, and stores with their main entrance to the right side sell more than their counterparts with doors on the left.

They also like to welcome us most graciously. When getting groceries, we're bombarded with beautiful, fresh produce, setting the tone for the rest of our beautiful, fresh shopping trip. Department stores display their newest, boldest, high-end pieces, promising us we're in for a quality experience. When I went to Target, I'd filled my cart with $5-worth of one-dollar deals within seconds of entering the store. It's all about first impressions.

In essence, stores trick our sense of sight to make shopping as addictive an experience as possible. And they do it all by taking advantage of our brain's dopamine reward system.

New things are exciting to animals. A number of studies have demonstrated surges in midbrain dopamine when rats explore unknown objects or suddenly discover novel compartments in their cages—not unlike checking out a new store in the mall or running our hands along the softest new J. Crew cashmere sweaters.

Since we get pleasure from window-shopping alone, can our shopping addictions stay in check so we're not buying everything we love in sight?

Work by Gregory Berns and colleagues at Emory University simulated novel experiences in humans lying in an MRI scanner. Participants received drops of water or Kool-Aid into their mouth; sometimes the drops were predictable, while other times they were random. Although the sweet, delicious Kool-Aid produced some increased activity in the brain's dopamine reward system, the activity was significantly elevated when administered unpredictably.

"You see the shoes and get this burst of dopamine," Berns explains. "It's like this fuel injector for action, but once they're bought, it's almost a let down."

And thus they sit in your closet, untouched—just like all those unread books and unwrapped DVDs and video games.

So what will you do the next time you're enticed by the freshest produce, softest sweaters, and prettiest pumps—stick to your shopping list, or buy out the store?

Pragmatically, it's easy for me to resist on a graduate student budget—but hopefully Target won't be charging me soon for all the dings and dents I made on their displays with their ridiculous shopping carts.

Berns GS, McClure SM, Pagnoni G, & Montague PR (2001). Predictability modulates human brain response to reward. The Journal of Neuroscience, 21 (8), 2793-8 PMID: 11306631

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