This Is What Your Brain Looks Like on a Shopping Spree

— -- The proliferation of cheap, chic and fast fashion, stores like H&M, Forever 21 and Zara have made shopping a euphoric, almost addictive experience for many, creating a billion-dollar industry.

Research from the University of Michigan shows that the desire consumers feel when shopping can make buying hard to resist every time they walk in, whether they need the item or not.

Thirty-year-old Alex Roberts spends most of her free time on the hunt for that next outfit. She says she spends up to $500 a month on her shopping habit. Many of the clothes in her closet still have the tags on them.

“It is my cardio,” Roberts told ABC News’ “Nightline.” “I feel so excited and pumped up when I do go shopping ... it’s kind of like a drug.”

Watch the full story on ABC News' "Nightline" TONIGHT at 12:35 a.m. ET.

To find out if shopping really is like a drug, “Nightline” attached a GoPro camera to Roberts as she hit up her favorite stores. A new technology called facial tracking was able to determine if she was experiencing euphoria like a high while shopping.

At Zara, Roberts came across a pair of camouflage-printed pants that she said she had been in search of for a year and started to feel like she had to purchase them. And inside her brain, analysis provided by a facial tracking company called Nviso said Roberts was on a shopping high. Her eyes were open and alert and her mouth slightly open -- signs that the pleasure center in her brain was lighting up, which experts at University of Michigan say is comparable to the joy felt after having sex.

“I was super excited, and I was more excited with the size and the price,” Roberts said of finding the pants. “It was like, ‘This is meant to be. It’s right. I have to get these.’”

While at Forever 21, Roberts seemed to be enjoying herself, but according to the facial tracking software, her brain said something else.

According to Nviso, her quick tightening of her lips and visual scanning of items indicated that she was disappointed and felt stress. Though she scored three items under $90 at the store, her stress level showed that she may have felt compelled to buy the clothes because they were so cheap.

“I definitely find some awesome pieces at Forever [21]. It’s so inexpensive I don’t even look at price tags when I go in there,” said Roberts.

University of Michigan Ross School of Business assistant marketing professor Scott Rick and his team of researchers took an even closer look at shoppers using facial tracking and actually scanning shoppers’ brains.

“We decided to ask the brain rather than the person. So we had people shop while having their brain scanned with functional MRI,” Rick told “Nightline.” “We found again some subtle emotions underlying these shopping decisions.”

Rick said there was evidence of pleasure and activation in regions that are targeted by dopamine in the shoppers’ brains, and the similar brain region that underlies the craving for drugs, sex or friends also appeared to be active while shopping. The more the subject wanted an item, the more the frontal cortex of the brain lit up. And if the price was right, there was even more activity.

“There is this pain that’s associated with the spending, and to the best that we can tell, there seems to be this trade-off. It's waning off of pleasure versus pain when we are making that shopping decision,” Rick said.

So because spending can cause stress, the pleasure has to outweigh the pain in order for someone to buy something, according to Rick. This is why low-priced, fast fashion is so hard to resist.

Besides keeping prices low, retailers use dozens of other tricks to lure customers to buy more. Michelle Madhok, who analyzes retail and marketing trends, knows these tactics all too well.

“These stores are set up to set off your brain. They’re hitting something at your human behavior that makes you want to buy,” Madhok told “Nightline.” “There’s the lights, the music. Sometimes they smell good, so it’s really immersing yourself in the feel-good experience.”

Roberts said learning the science behind her shopping habits still won’t deter her from getting that fashion fix.

“Finding a good deal makes me really happy,” Roberts said. “If I can get something for under $100 or under $50, I get very excited. And then I want to buy more.”