German and Cameroonian kids were part of an experiment based on the classic "marshmallow test": Put a single treat before a child but tell the child if he or she waits, say, 10 minutes, a second treat will be given.
Nathalie Dieterle for NPR
Cameroonian soldiers stand guard at a lookout post on Feb. 25 as they take part in operations against the Islamist extremist group Boko Haram in northern Cameroon, near the border with Nigeria.
Edwin Kindzeka Moki/AP
No one knows how many children have been affected by the spread of Boko Haram across Nigeria and neighboring countries. This photo shows the school uniforms of the girls kidnapped from a school a year ago.
Glenna Gordon/Glenna Gordon for NPR
A child receives a polio vaccine Sunday in Kano, Nigeria. The country is the primary source of the virus in Africa but appears to be making progress against the disease; the current outbreak in Cameroon that has spread to Equatorial Guinea came by way of Chad, not Nigeria.