A laugh that prompts you to cry out, "That tickles!" activates different brain areas than a laugh not provoked by tickling, a new study from Germany suggests.
In the study, about 30 men and women in their 20s were tickled for science — they had their feet tickled by a friend or partner while their brains were scanned in a functional magnetic resonance imaging (fMRI) machine. Separately, participants were asked to produce a laugh voluntarily (not in response to a joke) inside an fMRI machine, which measures blood flow to different areas of the brain to provide a real-time map of brain activity.
Both ticklish laughter and voluntary laughter activated the Rolandic operculum brain region, which is located in the primary sensory-motor cortex and is involved in movements of the face; both laughter types were also linked to activity in brain regions involved in vocal emotional reactions, such as crying.
However, only ticklish laughter activated the hypothalamus, a part of the brain involved in regulating many functions, including visceral reactions, the researchers said. [Which Animals Are Ticklish?]
Ticklish laughter also activated parts of the brain thought to be involved in anticipation of pain, which supports the idea that people who are tickled react defensively, the researchers said.
Ticklish laughter appeared to activate the same brain networks seen in earlier studies of humorous laughter. However, humorous laughter also activates an area of the brain involved in "higher order" functions, as well as a part of the brain called the nucleus accumbens, which is thought to be part of the brain's "pleasure center." Ticklish laughter did not activate these areas.
The results, which will be detailed in the June issue of the journal Cerebral Cortex, confirm the idea that ticklish laughter is a "building block" of humorous laughter — an idea first proposed by Charles Darwin and Ewald Hecker in the late 1800s, the researchers noted.
The study was conducted by researchers at the University of Greifswald in Germany, and researchers at the University of Fribourg and University of Basel in Switzerland.