Their antennae go up when they see the words "clearance," "markdown" or "closeout."
Impulse buyers have a keen sense of sight. They can spot a bargain from three aisles away.
The American Marketing Association describes impulse buying as "a purchase made without planning." Often the purchase is an emotional reaction to a marketing stimulus.
"It's fair to say I'm a shopaholic," says Linda Stauffer, 41, of Indianapolis. "Sometimes I just buy because it's inexpensive. I have a sister-in-law who has the same tastes I do, so sometimes I buy for her."
About 23.6 million Americans are compulsive shoppers, according to a Stanford University study. Earlier this year, the Commerce Department reported that U.S. consumers spent more than they earned in 2005. The result was the country's first negative rate of saving since the Great Depression.
Could impulse shopping bust your budget? Possibly.
Stanford University researchers say compulsive shopping can lead to serious psychological, financial and family problems, including debt. Antidepressants might be prescribed for those with uncontrollable spending urges.
But Stauffer says she's not in that category.
"I love shoes, but I really like it when I can buy a $10 sweater that someone else paid $80 for," said Stauffer.
"I have a lot of winter sweaters hanging in my closet with the tags still on them. They were bargains at the time," she says. Stauffer also stocks up on practical items like gifts, and stores them away for special occasions.
Future Foundation, an international marketing consulting service, reports gender differences in unplanned purchases. Women's are highest in food, clothes and toiletries. Men binge mostly on mobile phones and home electronics.
Roland Black, 35, hates to shop, but he recently left an Indianapolis shopping mall with an unplanned purchase — a holiday CD, marked down 70 percent. What would typically cost him $20 was $6.
"I usually shop for bargains. When I grocery shop, I'll buy extra loaves of bread if it's on special. And if there's a cooking demonstration, I might try out a new product if it's a good deal," says Black, a married father of three.
Shoppers like Black might not realize it, but they're the targets of savvy retail strategists. The holiday CD display was front and center at the music store.
Attractive packaging and eye-catching displays are directed at impulse buyers, says Ramon Avila, a Ball State University marketing professor.
"You go into the store to buy sausages, and the display includes chips, buns and soft drinks, and the next thing you know, you've bought a whole picnic," says Avila.
"Every grocery store manager has a job to increase revenue. Sometimes they do that by placing candy, magazines and batteries near the checkout counter so last-minute purchases will pull up the shopping basket prices."
Experts say impulse buyers need to be aware of marketing techniques that pull them in, and learn to avoid those traps. For example, if you walk by an in-store cooking demonstration, but sausage isn't on your list, just keep walking.
Impulse buyers need to change their shopping habits or avoid grocery stores and malls, says Suzon Tropez, a Texas-based financial analyst. "People shop for different reasons — they're bored, want a pick-me-up, or they're not paying attention to what they're doing."
She suggests that spenders ask themselves the following questions before purchasing: "Do I need this? Can I afford this? Can I pay my bills if I charge this?"