Since 1999, Scientists have wondered whether the sound that rats make when they are tickled, is actually a result of laughing. In this video by the National Geographic, so researchers at Humboldt University in Berlin have been trying to find out what happens in the brain, when we are tickled - in the aid of Science!
The researchers found out that rats do actually "giggle" when they are tickled, but at frequencies that humans can't hear. They also found out that the rats developed a fondness for human hands tickling them to the point that, when the tickling stopped, the rats looked to see where the hand had gone and did not turn away! In fact they treated the researcher's hand as a playmate and started to come back for more tickling!
The scientists observed the rats ticklishness and tried to work out how the brain actually processes the tickling sensation to try and get to the bottom of the feeling of ticklishness and why it makes us (and the rats) laugh :)