Laughter

09/20/2014 - We all laugh.  And you'll find that humor has very little to do with it.  We ask what makes us laugh? Along the way, we tickle some rats, listen in on a baby's first laugh, talk to a group of professional laughers, and travel to Tanzania to investigate an outbreak of contagious laughter.

http://www.radiolab.org/story/91588-laughter/