Rats Love Being Tickled

Freudensprungen! That, as the New York Times explains, happens to be the scientific term for jumping for joy, and a new study reveals that rats are among the animals that partake. The study, in fact, also shows that rats love to be tickled and that they burst out in the equivalent of rat laughter during the tickling. That laughing part was previously known, but the new study sheds light on what's going on in the brain. In the research, neuroscientists from Germany's Humboldt University tickled young male rats in various ways and outlined their findings in Science, reports the Los Angeles Times. Among the revelations: a stressed-out rat has no interest in being tickled, but the same rat essentially giggles when tickled under better circumstances. (It's too high-pitched for humans to hear.)

"They were so excited," animal psychologist Shimpei Ishiyama tells Smithsonian. "They were jumping around and they chased my hand. Pretty much like human kids, giggling and chasing around." For the record, the belly seems to be the sweet spot. The point of all this? Tickling is actually kind of a puzzle to scientists, and they're trying to unravel its mysteries. Researchers tracked brain activity and found that certain cells fired during the actual tickling and even while the rodents were merely chasing the tickler's hand. The latter part was a surprise, but a bigger one was that if researchers stimulated those same brain cells with an electrical current, sans tickling, the rats behaved as if they were being tickled, reports Science. "Maybe ticklishness is a trick of the brain to make animals or humans play or interact in a fun way," speculates co-researcher Michael Brecht. (City rats will not find this development at all funny.)