Asked by: Toby Graham, Shrewsbury
It’s all down to the lack of surprise. A 1998 study at University College London found that, when someone tries to tickle themselves, the brain reduces the intensity of the sensation by damping down signals in the somatosensory cortex – the brain region that processes touch.
If someone else tickles us, however, the brain doesn’t know what’s coming, and this mechanism doesn’t kick in – and we bear the full brunt of the tickling. This probably evolved so that we are able to differentiate between our own touches and those of another animal, such as a bug that could sting or transmit disease.