We all laugh. This hour of Radiolab asks why.

If you look closely, you'll find that humor has very little to do with it. We ask what makes us laugh, and how it affects us. 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.

***Is Laughter just a Human Thing?

***How Does Laughing Affect Us?

***Contagious Laughter

[February 25, 2008]