Where is the starting line of life?

Conservatives have little patience for no-strings-attached transfers, but many are amenable to things like vocational training. Such programs seem like straightforward ways to expand opportunity. Offer classes and guidance to people who seek to learn new skills and become more attractive hires. That’s how you offer a hand up—and that beats a handout eight days a week.

It may not be that easy. In their new book Scarcity, behavioral economist Sendil Mullainathan and psychologist Eldar Shafir complicate that distinction. They note that many poor people fail to follow through on promising opportunities—even, curiously enough, when money is no object. Across the world, poor people are disproportionately unlikely to get their children vaccinated even when all they have to do is sign up; they are disproportionately reluctant to wash their hands even though this is cost-free. Low-income Americans on Medicaid, which pays for their prescriptions, still fail to take their medication regularly.

This phenomenon defies the assumptions of standard economics. People whose lives are teetering on the brink have more incentive than anyone to seize on free and low-cost opportunities to improve their lot. But, the data show, they are in fact the least likely group to take advantage of these opportunities. What gives?

Mullainathan and Shafir developed several experiments to find out.