We’ve not uncovered a lot of evidence that the animal kingdom is rich in yuks and one-liners, but maybe we just didn’t know what to listen for. In this month’s issue of Scientific American, cognitive scientist Jesse Bering tells about recent research that suggests that rats can laugh. Not that you’d recognize their laughter as such. “Rat laughter comes in the form of high-frequency 50-kilohertz ultrasonic calls, or ‘chirps,’ that are distinct from other vocal emissions in rats,” writes Bering. So, no ha-ha’s.
How do you crack a rat up? You tickle him. The study, conducted by researcher Jaak Panksepp, found similarities involving chirping in young rodents and laughter in young children during rough-and-tumble play. For instance, just like children, rats that enjoyed being tickled would seek out human hands that had tickled them before. And, if given a choice, young rats spent more time with adult rats that were inclined to chirp/laugh than with those that didn’t.
This shouldn’t suggest that rats have a sense of humor, which requires complex cognitive mechanisms that are not proven to exist in nonhuman species. So you still can’t expect them to chuckle at “Ratatouille.”
In a special issue, Discover magazine explores how science exposes invisible worlds — places, organisms and processes that we can’t regularly access because they’re temporally or geographically distant or just really small. There’s a piece on researchers who are looking for tetrachromats, people who can see 100 million colors — far more than the average human — because their eyes have four types of cone cells instead of the typical three. But these people are hard to find, since perceiving color is entirely personal and these rare individuals have no way of knowing that what they see is in any way special. There are also items on scientists mapping out the habitats of household microbes and the gradual migration of our planet’s continents into a single landmass, a process that will take place over the next 100 million years. And there’s a piece about the science of actually making things invisible, which lists ways that scientists might be able to deflect light.