Different kinds of jokes are processed in different parts of the brain 鈥� but the amusement they cause is experienced in a single place.
Jokes are funny partly because they lead you along one line of thought, only to take you in an unexpected direction. Vinod Goel at York University in Toronto and Raymond Dolan of the Institute of Neurology in London were interested in knowing where in the brain this mental shift takes place.
The researchers used functional MRI to scan 14 healthy people while they listened to two types of jokes. Half the jokes were 鈥渟emantic鈥�, for instance, 鈥淲hy don鈥檛 sharks bite lawyers? Professional courtesy鈥�. The other half were puns, such as 鈥淲hy did the golfer wear two pairs of pants? He had a hole in one.鈥� Control jokes were set-ups with punchless punchlines.
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To their surprise, the researchers found that the different jokes were processed in completely different brain areas. 鈥淲e did find the shift,鈥� says Goel, but where it occurred depended on the joke type. 鈥淭here was no central area.鈥�
Semantic jokes used a bilateral network in the temporal lobes, whereas the puns used areas near those for speech production, on the left side.
Laughing out loud
The jokes were intentionally lame, admits Goel, because they didn鈥檛 want the volunteers to laugh out loud and move their heads inside the scanner. Nonetheless, volunteers were asked to rate them according to how funny they found them.
Intriguingly, when the volunteers found either kind of joke genuinely funny, they always activated another part of their brain, known as the medial ventral prefrontal cortex.
This 鈥渇unny spot鈥� only responded when the joke was amusing 鈥� 鈥渘ot if it was stupid, old or offensive,鈥� says Goel. And the more they liked a joke, the more the area lit up, the researchers report in the current issue of Nature Neuroscience (vol 4, p 237).