What do you do when you're feeling down? Eat a carton of ice cream? Drink a few beers? Read war poetry? Maybe you go shopping. Researchers at Harvard, Carnegie Mellon, Stanford, and Pittsburgh universities have released the results of a new study, finding that sad and self-absorbed people tend to spend more.

The scientists ran an experiment where one group of participants watched a depressing video about a boy whose mentor dies, while another group watched a more neutral program on the Great Barrier Reef. Then participants were asked how much they'd pay for a "sporty-looking, insulated water bottle." Those who'd seen the sad program offered nearly four times as much money as those who watched the nature program.

An Associated Press article noted that as opposed to "retail therapy," where people consciously take themselves shopping in order to feel better, they're generally unaware of this kind of sadness-induced over-spending. It can, after all, occur in relation to something someone might have planned to buy regardless of mood, and its effect is simply to lead the consumer to spend more.

How could retailers capitalize on this information? This cynical financial writer wonders if you'll start seeing Wal-Mart (NYSE: WMT) or Best Buy (NYSE: BBY) playing reruns of "Old Yeller" or "Titanic" on HDTV monitors to get customers in the buying mood. Starbucks (Nasdaq: SBUX) could pipe in sad music, and web retailers like Amazon.com (Nasdaq: AMZN) could put up full-scale graphic designs meant to depress customers and thus spike sales.

What's going on -- and what to do about it
So how can this phenomenon be explained? The key seems to be how self-focused we are. Sadness can prompt us to circle in on ourselves, focusing on our feelings more than usual. Scientists measured the degree to which study participants were self-focused by counting how many times they used words such as "I," "me," etc. in their writing. They believe that "sadness can trigger a chain of emotions leading to extravagant tendencies." When sad, people often increasingly focus on themselves, eventually feeling worthless (or worth little). In order to combat this feeling, they spend more.

It's good to be aware of any tendency to spend more when you're feeling down. In the course of your routine purchases, occasionally ask yourself whether you're buying something you really need, or simply trying to make yourself feel better. Don't short-change your critical savings.

Learn more in our Savings Center, and here:

Longtime Fool contributor Selena Maranjian owns shares of Wal-Mart and Starbucks. Best Buy and Wal-Mart are Motley Fool Inside Value recommendations. Amazon.com, Best Buy, and Starbucks are Motley Fool Stock Advisor recommendations. Try our investing services free for 30 days. The Motley Fool is Fools writing for Fools.