The exploration into cardholders’ minds hit a breakthrough in 2002, when J. P. Martin, a math-loving executive at Canadian Tire, decided to analyze almost every piece of information his company had collected from credit-card transactions the previous year. Canadian Tire’s stores sold electronics, sporting equipment, kitchen supplies and automotive goods and issued a credit card that could be used almost anywhere. Martin could often see precisely what cardholders were purchasing, and he discovered that the brands we buy are the windows into our souls — or at least into our willingness to make good on our debts. His data indicated, for instance, that people who bought cheap, generic automotive oil were much more likely to miss a credit-card payment than someone who got the expensive, name-brand stuff. People who bought carbon-monoxide monitors for their homes or those little felt pads that stop chair legs from scratching the floor almost never missed payments. Anyone who purchased a chrome-skull car accessory or a “Mega Thruster Exhaust System” was pretty likely to miss paying his bill eventually.

Martin’s measurements were so precise that he could tell you the “riskiest” drinking establishment in Canada — Sharx Pool Bar in Montreal, where 47 percent of the patrons who used their Canadian Tire card missed four payments over 12 months. He could also tell you the “safest” products — premium birdseed and a device called a “snow roof rake” that homeowners use to remove high-up snowdrifts so they don’t fall on pedestrians.

Testing indicated that Martin’s predictions, when paired with other commonly used data like cardholders’ credit histories and incomes, were often much more precise than what the industry traditionally used to forecast cardholder riskiness. By the time he publicized his findings, a small industry of math fanatics — many of them former credit-card executives — had started consulting for the major banks that issued cards, and they began using Martin’s findings and other research to build psychological profiles. Why did birdseed and snow-rake buyers pay off their debts? The answer, research indicated, was that those consumers felt a sense of responsibility toward the world, manifested in their spending on birds they didn’t own and pedestrians they might not know. Why were felt-pad buyers so upstanding? Because they wanted to protect their belongings, be they hardwood floors or credit scores. Why did chrome-skull owners skip out on their debts? “The person who buys a skull for their car, they are like people who go to a bar named Sharx,” Martin told me. “Would you give them a loan?”

Some credit-card companies began using these and other discoveries to find new customers and to scrutinize existing cardholders. A few firms began sending offers to people who had registered for baby showers or weddings, for example, since data showed that getting married or having a child — in addition to making people buy lots of new stuff — often also makes them more responsible. Other companies started cutting cardholders’ credit lines when charges appeared for pawnshops or marriage therapy because data indicated those were signs of desperation or depression that might lead to job loss.

But on the whole, companies, including Canadian Tire, stuck to more traditional methods of managing risk, like raising interest rates when someone was late paying a bill, because they worried that customers would revolt if they found out they were being studied so closely.

“If you show us what you buy, we can tell you who you are, maybe even better than you know yourself,” said Martin, who now works for Wal-Mart Canada. “But everyone was scared that people will resent companies for knowing too much.”

Then last year, the economy blew up. Three things became obvious very quickly. First, all those extra charges that theoretically protected credit-card companies from losing money? Well, the worst-case models were way off, and some companies started hemorrhaging cash. Second, many of the predictions that card companies built around their understandings of people’s psyches were surprisingly accurate, even during an economic tsunami. And finally, when people start losing their jobs and feeling poor, it suddenly becomes very, very important to figure out how to persuade them to pay their credit-card bills.