Ten years ago when neuroscientist Jaak Panksepp published his research showing that rats laugh when you tickle them, he might have gotten laughed off the stage. Most people still thought that “sophisticated” emotions like laughter required the kind of consciousness that we associate only with humans. But Panksepp’s research is winning them over. Panksepp says,

Although some still regard laughter as a uniquely human trait, honed in the Pleistocene, the joke’s on them.

For more info, see John Tierney in the New York Times. For an accessible essay by Panksepp, see “Beyond a Joke: From Animal Laughter to Human Joy?” Science, 1 April 2005. Thanks to Sandy Hockenbury of Boulder Media Women for the heads-up.