New research has found that men's and women's brains process humor in different ways, and that personality types may also play a distinctive role in how people perceive things as funny or not.

When shown a funny cartoon, women showed more activation in the parts of the brain involved with feelings of reward, as well as language processing and working memory.

The findings, appearing in this week's issue of the Proceedings of the National Academy of Sciences, have implications that are no laughing matter.

"It's been well-documented that women tend to experience symptoms of depression twice as much as men," said Eiman Azim, a doctoral student in neuroscience at Harvard University who conducted the study while an undergraduate student at Stanford University. "This type of questioning might help us understand why emotive processing in women is different, and why they experience depression differently."

The research may also one day help individuals with cataplexy, a condition in which a sudden loss of motor control is set off by strong emotions, especially humor, the researchers said.

Both the brain's prefrontal cortex (important for language processing and memory) and the mesolimbic reward center are known to be activated by humor.

While some past studies had shown gender differences in how humor is used and appreciated, no one has yet looked at gender-based differences in how the brain responds to humor.

For this study, 10 females and 10 males underwent functional magnetic resonance imaging (MRI) while viewing 70 black-and-white cartoons. They were asked to rate each cartoon on a "funny scale," with 10 being the highest rating.

The behavioral responses to the cartoons, including reaction times, were essentially equivalent in the two groups. "It's not that they were getting something different out of the humor, or enjoying it differently," Azim said.

Many of the same brain regions were also used.

But there were differences, and the differences were surprising. During funny cartoons, women showed greater activation in the prefrontal cortex and the nucleus accumbens (NAcc), which is part of the mesolimbic reward center.

"It was surprising to find it in the two regions where we found it, but finding differences was not surprising," Azim said. "Men's and women's brains have evolved to process cognitive and emotive information somewhat differently. Looking at humor starts to reveal subtle differences in processing strategies."

The NAcc finding was the most surprising. This region is activated in all kinds of rewards, such as when you win at gambling or take cocaine.

"Females tended to activate this region more than men, and men tended to inactivate it during unfunny cartoons," Azim said.

Women also had more activation the funnier the cartoon was, while men tended to deactivate the center when they encountered an unfunny cartoon.

What does this mean?

"Females seem to be anticipating the reward less than men, and have greater activation when they get it," Azim explained.

If women's reward centers are more sensitive to stimuli, this may help explain the higher rate of depression among women, Azim said.

"It's a hypothesis, and more studies need to be done to verify it," Azim cautioned. "It indicates that there is a distinct strategy in ways men and women process humor, even though they are enjoying it the same."

A related study in the same issue of the journal found that personality traits, including extroversion and introversion, also have a bearing on how humor is processed.

- More articles on Laughter

Reference Source 101
November 8, 2005