Liza Gross

Packed with nutrients, easy to grow and adaptable to local cuisines, this tropical superfood could bring more food and cash to poor farmers around the world.

Although vaccines are among the safest, most effective ways to protect children from major communicable diseases, some parents still doubt this. As a result, some choose immunization schedules that defy science or refuse to vaccinate altogether.

If these parents were distributed randomly, their decisions would be less likely to ...