PORT-AU-PRINCE — Outside my window, I hear a musical sound. Pa-Ping! Pa-Ping! It stops for a few seconds, then starts again. Ping! Ping! It goes on for half an hour — Pa-ping! Ping-ping-ping! — until finally, I drag myself out onto the morning heat to see if someone left an alarm going somewhere.
No alarm. It’s the sound of a language program being studied by Bianka, one of our teenaged girls. The program is called Duolingo. Every time you answer a question correctly, you get a ding.
