In a series of studies, Harvard University economist Sendhil Mullainathan and Princeton University psychologist Eldar Shafir found that being poor, and having to manage serious financial problems, can be a lot like going through life with no sleep. The reason is that if you are poor, you are likely to be preoccupied with your economic situation, and your mind has less room for other endeavours. This claim has important implications for how we think about poverty and for how we select policies designed to help poor people.