For the past five days, most of us have been focused on the news from Paris and Belgium, as events there continue to unfold after Friday’s attacks. We’ve learned a lot about ISIS from those news reports. But there’s another group, one that is even deadlier, that you’re not hearing much about. The Nigerian militant group Boko Haram has killed about 20,000 people during its six-year reign. Just this week, two markets in Nigerian cities were bombed, killing dozens of people who were out shopping. Boko Haram is suspected in both incidents. An Al Jazeera reporter who's covering the conflict explains who they are and what they're after. Then a psychology professor explains why the human mind has trouble processing soaring death tolls, and why that might encourage indifference to the actions of groups like Boko Haram. Plus, we catch up with radio producer David Isay. Before he founded StoryCorps, he produced a groundbreaking documentary. We revisit Ghetto Life 101.