“Mostly because my credit card is giving me lots of miles,” he said.

This is exactly what the credit card companies want us to think, and the math works for them. They buy the frequent-flier miles for a penny or two each from the airlines (or mint their own points that cost them a similar amount) and sit back and hope that we will pay lots of interest or at least buy more than we otherwise would have.

Mr. Srivastava, a professor of marketing and consumer psychology at the Robert H. Smith School of Business at the University of Maryland, pays his bill off each month and doesn’t think he falls victim to the credit card premium. When he was doing the research that led to the paper, he switched to using a debit card for a while to establish his baseline for expenses. Now, he watches carefully to make sure he doesn’t exceed that level when using a credit card.

Priya Raghubir, Mr. Srivastava’s co-author, happened to be moving to New York City when their research was published in 2008. “I’ve never in my life been in greater debt,” she said, laughing at the memory now. “I knew all about how credit cards work, but it wasn’t my fault. All you need to do to take a taxi here is swipe a card.”

Six years later, her spending is more under control. She has experimented with using cash as much as possible and trying to see how long a large withdrawal could last, but it made her feel poor. Some of her recent academic research at New York University’s Stern School of Business, where she is a marketing professor, led her to a new credit card that delivered more rewards. She noted proudly that her son had taken the research to heart, controlling his spending by using cash for discretionary purchases when he goes out.

When I told Drazen Prelec, co-author of the “Always Leave Home Without It” research, which cheekily alluded to the old American Express slogan, about my own rewards lust, he suggested that it might be time for some therapy. I had hoped that he would set me straight himself, but he has his own uneven history with the incentive industrial complex.