Rats laugh when tickled.
Scientists are finding there is a long evolutionary trail to our odd noises of amusement, and the latest proof comes from ticklish rats.
You've probably never heard a rat laugh, and there's a good reason.
Jaak Panksepp, of Bowling Green State University in Ohio, and his students found that the rodents emit gleeful "chirps" when playing, but only at ultrasonic tones five times higher than the human ear can hear. Once Panksepp hooked up an ultrasonic detector to listen in on rats in his lab and started tickling the animals, he realized the effect on them was dramatic.
"We used our hands as if they were playmates and pounced and tickled the rats with our fingers. The chirping sounds were out of sight, just out of sight," said Panksepp, who wrote about the studies in this week's issue of the journal Science. "The animals became bonded to you and came back for more. Every possible measure of whether they like it shows yes, they love it."
Not only did the rats respond instantly to the tickling, after awhile, they reacted the way a child often does before a tickling hand even reaches them.
