Scientists have long recognized that poverty can aggravate health problems. Now they're also beginning to understand that the stress of too little income actually changes the way people think. Princeton psychologist Eldar Shafir says that's normal for someone who's not making ends meet. He studies the brain on scarcity. He says it doesn't matter what kind of scarcity you're dealing with. When humans don't have enough of something, that fact dominates our consciousness.
