Wanna hear primates laugh? It's infection, I guarantee it! Audio samples within.
Primatologist and psychologist Marina Davila Ross of the U.K.'s University of Portsmouth led a team that tickled the necks, feet, palms, and armpits of infant and juvenile apes as well as human babies. The team recorded more than 800 of the resulting giggles and guffaws.Apes Laugh, Tickle Study Finds (Thanks, Marilyn!)