"The optimist in me says in three years we can train this tool to read mammograms as well as an average radiologist," says Connie Lehman, chief of breast imaging at Massachusetts General Hospital in Boston. Kayana Szymczak for NPR hide caption

President Trump at the signing ceremony for the First Step Act in December. While some prisoners are benefiting from reduced sentences, implementation of other aspects of the law has been hit with delays. Jim Watson/AFP/Getty Images hide caption

This illustration made available by NASA shows the Kepler space telescope, the planet-hunting spacecraft that launched in 2009. NASA via AP hide caption

Arthur Brooks, seen speaking at Georgetown University in 2015, has a new book called Love Your Enemies: How Decent People Can Save America from the Culture of Contempt. Pablo Martinez Monsivais/AP hide caption

A Rhode Island resident holds an envelope he received for the 2020 census test run in Providence County. Hansi Lo Wang/NPR hide caption