Ever wondered why humans feel ticklish?

Are you ticklish? And if so, are you only ticklish in certain places? Does it serve a purpose?

Researchers have been tickling rats to see if the furry rodents can offer clues.

Berlin researchers Michael Brecht and Shimpei Ishiyama used electrodes implanted in the rats' brains for deeper investigation of the tickling and ­concentrated on an area where we (and rats) perceive touch called the ­somatosensory cortex, reports the Mirror.

Somatosensory cortex is the main sensory receptive area for the sense of touch.

As the result of some recent research, experts say tickling and being tickled has evolved so we interact, laugh, have fun and bond closely.

The link to play and emotions in the somatosensory cortex is also intriguing, while the similarity of tickling in rats and humans is, Dr Brecht said, "amazing".

They pointed out in their report that tickling raises many questions.

Since then they found a way of recording brain activity while playing with the rats. So, researchers can track what's going on in their brains while they're being tickled and "laughing".

"The team first accustomed young rats to play and tickling which they would invite. "They are very eager to be tickled," said Dr Brecht.

"We still don't understand how moods affect behaviour and learning more about them would be very important in psychology," Dr Brecht explained.

That similarity he says, suggests that tickling, in evolutionarily terms, is very ancient, going back to the roots of touch as a way to form social bonds in the ancestors of rats and humans.

"Maybe," Dr Brecht speculated, ­"ticklishness is a trick of the brain to make animals or humans play or interact in a fun way.