Consumers fancy themselves immune to this financial anesthesia. But study after study has documented credit cards’ ability to get people to spend more than they otherwise would, even when cash, credit, and debit were randomly assigned to experimental subjects: Credit cards make people more likely to forget how much they spent on something. They make frugal people spend recklessly. They make people willing to spend a lot more on one-off purchases. And large credit limits promote the illusion that daily purchases are inconsequential.

A seminal 2001 study by Drazen Prelec and Duncan Simester titled “Always Leave Home Without It” firmly established a “credit card premium” that arises under certain circumstances. That premium was identified decades earlier, by Richard Feinberg, a professor of consumer behavior at Purdue University, in a 1986 study. Feinberg's experiments suggested that simply seeing a credit-card logo was enough to make people willing to spend more money on a product.

Prelec and Simester’s findings downplayed the importance of logos, but further solidified the theory that credit cards extract more money from people than cash in identical circumstances. The two researchers found that their Boston-based experimental subjects were willing to pay strikingly different amounts of money on tickets to a Celtics game, depending on their method of payment. Those paying with cash found roughly $30 to be a reasonable price, while those paying with credit on average were satisfied with $60. This Celtics experiment suggests that the premium is largest and most dangerous when people are making one-off purchases or buying things with uncertain value.

“Twice as much” is a finding so outlandish that many will consider themselves exempt from credit cards’ dark magic—in fact, even the people who have rigorously studied it themselves use credit cards. Prelec told The New York Times last year that he uses one occasionally—only to book travel or make big purchases, which, he claims, doesn't violate the recommendations of his own research. The University of Maryland’s Joydeep Srivastava, the author of another study scrutinizing plastic, still uses one too. “Mostly because my credit card is giving me lots of miles,” he explained to the Times.

There are without a doubt certain circumstances under which using a credit card is a good idea. If you need a cheap line of credit before a paycheck comes (and you’re absolutely sure you can pay off the bill), use a credit card. If you need to build good credit in order to get a loan, use a credit card. And if you have determined that a credit card’s perks make absolute total sense for you personally, use that credit card. (For example, one of my colleagues, an avid magazine reader, uses a credit card that gets her significant discounts on more than one of her subscriptions. Miles and cash-back programs, though, are often too stingy to justify risking the credit-card premium.)