Scientists have gone into the mysteries of tickling for centuries, with Aristotle asking why people don't feel a ticklish sensation when they tickle themselves. Many psychological and neurological studies have been carried out on the subject. Tickling has been associated with our ability to laugh, feel good, and play. And it seems that rats too behave in the same way as humans when tickled.
Usually, the life of a rat in a lab is not a pleasing one. They are starved, crippled, sliced, drugged and even shocked just for better scientific understanding. However, a particular group of German rats has been fortunate enough to become participants of a study on tickling.
Scientists from Berlin-based Humboldt University decided to study on the subject of rat tickling to find out what exactly occurs in their brain when it's tickled. The study, published on Nov. 11, 2016 in the journal Science, locates the "tickle center" in the brain, which gives rise to ultrasonic squeaks-similar to human laughter.
The findings can have enormous implications on human psychology, especially with respect to the significance of human touch in creating special bonds. According to the paper, rats emanate ultrasonic vibrations when tickled by humans, which takes place via dopaminergic mechanisms. Many similarities between human and rat ticklishness like tickling-evoked anxiogenic modulation and vocalizations, show that tickling is an extremely conserved and old kind of social physicality, states the paper.
When the neurons linked with tickling were stimulated artificially, researchers found the rats "laughing." However, when the rats were tickled in an anxiety-induced situation, they didn't elicit the same response, which shows that emotions certainly have an effect on the neuronal activity.
A fascinating thing about ticklishness is that is that it's dependent on the mood, said Shimpei Ishiyama, a scientist at the Humboldt University. Even Darwin once noted that kids tickled by an unfamiliar person had a tendency to scream rather than laugh, he remarked.