The science of MRI has officially confirmed what many people had already deduced for themselves--there is nothing funny about being tickled. Researchers at the University of Tuebingen in Germany used magnetic resonance imaging to scan the brains of 18 subjects, recording neural responses of three types of laughter: humorous and joyful laughter, mean-spirited, mocking laughter and tickling-induced laughter.
"Laughing at someone and laughing with someone leads to different social consequences," says Dirk Wildgruber, who led the study. "Specific cerebral connectivity patterns during perception of these different types of laughter presumably reflect modulation of attentional mechanisms and processing resources."
The researchers believe that the two types of laughter related to social interaction (joyful and taunting laughter) are more associated with the parts of the brain responsible for processing complex social information. However, all three types of laughter, including tickling, activate a part of the brain called the Rolandic Operculum, which is responsible for controlling facial movements as well as vocal and emotional reactions.
Interestingly, when participants of the study were tickled, an additional part of the brain was activated - the hypothalamus. The hypothalamus is associated with what is colloquially known as the 'fight or flight' response; this part of the brain controls instinctive reactions such as hunger and body temperature, fatigue levels and sexual behaviour.
Because tickling actually stimulates a nervous response in the brain associated with pain, the researchers concluded that laughter during a 'Tickle Torture' is actually an unconscious display of submission. This also explains why you'll get no response if you try to tickle yourself; your intelligent brain knows there is nothing to laugh about.