The study that scanned brains of 10 men and 10 women as they watched cartoons found out that while men and women got a kick out of the same cartoons, their brains responded in slightly different ways, Allan Reiss, a Stanford psychiatrist who led the study said.

The first-of-its-kind imaging study showed that women activate the parts of the brain involved in language processing and working memory more than men when viewing funny cartoons.

Their reward centers also lit up more intensely. This may be because they didn't expect the cartoons to be as funny as the men did, and so felt more intense pleasure when they got the punch line.

The results help explain previous findings suggesting women and men differ in how humour is used and appreciated, Allan Reiss.

Past studies have shown gender differences in the use and appreciation of humour and the meaning and function of laughter, but no previous research has examined sex-specific differences in the brain's response to humour.

After analysing the data, the researchers found that men and women share much of the same humor-response system; both use to a similar degree the part of the brain responsible for semantic knowledge and juxtaposition and the part involved in language processing.

But they also found that some brain regions were activated more in women.

These included the left prefrontal cortex, suggesting a greater emphasis on language and executive processing in women, and the nucleus accumbens, or NACC, which is part of the mesolimbic reward centre.

Reiss said he was taken off guard by the NACC finding. After puzzling over it, he and his colleagues theorised that because the women in this study used more analytical machinery when deciphering humorous material, it signaled that they were not necessarily expecting the cartoons to be as rewarding as did the men.

When a woman's brain encountered the punch line, her reward center lit up.

According to Reiss, the activation of this centre not only signals the presence of something pleasant, but that the pleasure was unexpected.

If subsequent studies show that women's reward centre and other regions of the brain are more sensitive to emotional stimuli, including negative stimuli, that could help explain why depression strikes twice as many women as men, potentially leading to new therapies, Reiss said.

The study's results also have potential implications for individuals who suffer from cataplexy, in which a sudden loss of motor control is precipitated by strong emotions, most notably humour.