Employment program representative Mark Robbins (L) explains unemployment insurance payments to a client at the Employment Development Department of California service office in San Francisco, January 6, 2012. REUTERS/Beck Diefenbach The daily pressures and stresses of poverty take up so much mental energy that it reduces cognitive function. According to a new study, published in Science today, being preoccupied with money can cause low income people to suffer a drop in IQ of 13 points on average.

A few comparisons highlight how severe that is. That difference in IQ is about the same as the gap between a chronic alcoholic and a normal adult, according to The Atlantic. It's comparable to the cognitive drop people see when they've just pulled an all-nighter.

In the researcher's first study, people across the income spectrum in New Jersey were asked how they would respond to a situation where their car suddenly required repair: Would they pay right away, borrow money, or put the repairs off for now. And how would they decide?

Before giving a response, they were run through a series of "common fluid-intelligence and cognition tests."

When the repairs were said to cost $150, poor and rich people performed cognitive tasks at the same level. When the number was $1,500, poor people performed far worse on those tasks, while wealthier individuals weren't affected.

Poverty is often blamed on "the personal failings of the poor," co-author Jiaying Zhao says. This is evidence that the situation itself hurts people's ability to concentrate and make decisions.

"Stress itself doesn't predict that people can't perform well — they may do better up to a point," Princeton professor and co-author Eldar Shafir says. "A person in poverty might be at the high part of the performance curve when it comes to a specific task and, in fact, we show that they do well on the problem at hand. But they don't have leftover bandwidth to devote to other tasks. The poor are often highly effective at focusing on and dealing with pressing problems. It's the other tasks where they perform poorly."

A second study looked at a more natural scenario, the abilities of Indian farmers who get the vast majority of their income after their harvest, but live under serious financial strain beforehand. Pre-harvest, they show the same strain and reduced mental bandwidth that the first study found in impoverished people. Post-harvest tests, conducted when the farmers were comparatively rich, resulted in higher scores.