Can Being Poor Lower Your IQ?

NEW YORK (MainStreet) — A low income is known to be associated with bad health, higher mortality and low education—that's horrible enough. And now new research published in the journal Science suggests the sheer strain of financial trouble siphons away enough mental power to cause a substantial drop in IQ.

The study, led by researchers Eldar Shafir and Sendhil Mullainathan, conducted two tests on vastly different people: shoppers in a New Jersey mall, and sugar cane farmers in India. In New Jersey, a sample of participants with incomes ranging from $20,000 - $70,000 were asked how they would fix a car requiring "X" number of repairs. The repair cost ranged from low to high. This first kind of problem solving served as a reminder about their financial situation. Then, participants were given IQ tasks, and here's what happened: the low income participants performed just as well as the more affluent when the X amount was low, around $150. But when the cost increased, the poor "performed significantly worse" than the rich, according to the study, suggesting the looming worry over money can affect cognition.

"In terms of working capacity—the number of things you juggle in your head—you have a limited capacity," says Shafir. He likens it to remembering a seven-digit number as an example: if you're struggling to remember it, you're not going to perform very well with another problem needing immediate attention. Likewise, if you're preoccupied with bills and always feel a need to keep an eye on every dollar spent, your mind might struggle with other tasks.

The second part of the study focused on Indian farmers who are only paid once a year, after harvest. Pre-harvest, they're very financially strained; afterwards they're not. The researchers conducted IQ tasks before and after the harvest, and found farmers did significantly worse on the tasks pre-harvest—a whole 13 IQ points lower, in fact, which is roughly equal to losing an entire night's sleep.