Humor hits men and women differently, new brain research shows.

The findings appear in Proceedings of the National Academy of the Sciences, a serious journal that’s not very giggly reading.

Two studies in the journal’s online edition pair humor with high-tech science. The results may be enlightening about how men’s and women’s brains handle emotions.

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Funny or Not?

The rules were simple:

—View a bunch of cartoons one by one.

—Press a button to call each cartoon funny or not.

—Rank the funny ones on a 1-to-10 scale (scarcely funny to absolutely hilarious).

—Meanwhile, get your brain scanned by functional magnetic resonance imaging (fMRI).

Ten women and 10 men did that. Eiman Azim and colleagues kept watch. At the time, Azim was a Stanford University undergraduate student; now, he’s a graduate student at Harvard University.

Both sexes found about eight out of 10 cartoons funny. Men and women mainly agreed about which cartoons were funny.

Their brains, however, handled humor differently.

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Her Brain, His Brain

When women found cartoons funny, their brain scans showed more activity in certain brain areas, including the nucleus accumbens.

When the women saw cartoons that didn’t tickle their funny bone, their nucleus accumbens had a ho-hum response.

Men’s brain scans were different. Their nucleus accumbens didn’t react to funny cartoons and showed a drop in activity with unfunny cartoons.

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Surprise may be at the heart of the study. Here’s the researchers’ theory.

Perhaps women didn’t expect cartoons to be funny, while men expected the opposite. When they got what they expected, their nucleus accumbens were calm.

When women were pleasantly surprised, their brain scans may have reflected that with a flurry of activity in the nucleus accumbens.

Men, on the other hand, may have been let down by unfunny cartoons, causing a dip in that brain area’s activity.

If so, it might be a new clue about emotional responses. That could prove interesting for depression research, write Azim and colleagues.

“The results help explain previous findings suggesting women and men differ in how humor is used and appreciated,” says Allan Reiss, MD, in a news release.

Reiss is Stanford’s Howard C. Robbins Professor of Psychiatry and Behavioral Sciences. He also directs Stanford’s Center for Interdisciplinary Brain Sciences research. Reiss worked on both of the new studies on humor.

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Personality, Humor, and the Brain

Personality was the topic in the second Stanford study.

The study also used cartoons and MRI brain scans. But first, the participants — eight women and nine men — took personality tests.

The tests covered neuroticism, extraversion, conscientiousness, and other traits.

Introverts and extraverts showed different brain activity patterns in viewing and rating the cartoons. But introverts didn’t necessarily laugh or smile more or less than extraverts, write the researchers.

They included Dean Mobbs, now a graduate student at University College London.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Azim, E. Proceedings of the National Academy of the Sciences, week of Nov. 7, 2005; online early edition. Mobbs, D. Proceedings of the National Academy of the Sciences, week of Nov. 7, 2005; online early edition. News release, Proceedings of the National Academy of Sciences.