Martha (right), an extinct passenger pigeon, at the Smithsonian's Natural history Museum in Washington. The passenger pigeon was once the world's most plentiful bird. Sept. 1 is the centenary of the bird's extinction. Susan Walsh/AP hide caption

itoggle caption Susan Walsh/AP

Lindolfo Carballo, an immigrant from El Salvador, meets his son, Raynel, outside school. In El Salvador, he says, families often "teach their boys one thing and their girls differently." He's trying to set a different example for his children. Sarah Tilotta for NPR hide caption

itoggle caption Sarah Tilotta for NPR

A recent study found a brief delay in peak growth spurt among boys who took ADHD stimulants for at least three years, but no significant effect on their ultimate height. iStockphoto hide caption

itoggle caption iStockphoto