What Happens When You Tickle A Rat?

Rats are used for all kinds of scientific experimentation, and many rats have given their lives so that scientists can figure out how to cure diseases, test theories and generally help mankind live longer and better.

But the rat in this video posted by National Geographic hit the jackpot, because he's the subject of an experiment on tickling!
Researchers at The Humboldt University of Berlin discovered rats vocally express enjoyment when they're tickled, just like humans do, and they like tickling so much they come back for more.

(YouTube Link)