Did you know that rats laugh when you tickle them? (I learn all sorts of interesting things from living with an animal behavior guy). Not only that, they vary the intensity of their laugh response depending on their level of enjoyment. Humans can’t pick up these high pitched giggles and guffaws without a bat-range listening device.

So, we humans can’t claim laughter as our exclusive domain– rats, dogs and chimps show signs of laughter and joy, too. Here’s more from a Perspective article in Science (requires a subscription).

Laughter seems to hark back to the ancestral emotional recesses of our animalian past (3, 4). We know that many other mammals exhibit play sounds, including tickle-induced panting, which resembles human laughter (2, 4, 5), even though these utterances are not as loud and persistent as our sonographically complex human chuckles (6). However, it is the discovery of “laughing rats” that could offer a workable model with which to systemically analyze the neurobiological antecedents of human joy (3). When rats play, their rambunctious shenanigans are accompanied by a cacophony of 50-kHz chirps that reflect positive emotional feelings (7). Sonographic analysis suggests that some chirps, like human laughs, are more joyous than others.

This isn’t brand new science: some of the rat studies date back more than 5 years. But there’s still a lot to learn– about how laughter is wired in the brain and about the emotional nature of animals. But I’m comforted that  laughter and joy seem to be so fundamental in brain development. And I’m happy to share a good chuckle with other members of the animal kingdom.