Seriously folks, scientists want to know what tickles people's funny bones, and they're looking into the brain to find out.

At Stanford University, Professor Allan L. Reiss and his colleagues are using a brain-scanning technique in combination with "Bizarro" and "Far Side" cartoons to see if activity in the gray matter between the ears reveals whether men and women react differently to visual humor.

At Dartmouth College in New Hampshire, students are laughing at the TV sitcoms "Seinfeld" and "The Simpsons" while being scanned by the same brain-scanning technique, known as functional magnetic resonance imaging or "fmri".

Strange as such research might appear to laypeople, "humor is quite amenable to scientific study," says neuroscience Professor Gregory S. Berns of Emory University, who wasn't connected with either of the brain-scanning studies.

Berns, who in a 2004 article for the journal Trends in Cognitive Sciences, wrote about Reiss' earlier studies of humor, said such studies must be conducted in the tightly controlled circumstances of labs like Reiss' because, as he noted with a chuckle, "we can't study people in a comedy club audience with fmri."

In their lab, Reiss and his four Stanford colleagues found that on the average, males and females seem to be amused - or not amused - by the same kinds of cartoons.

Yet, as they reported in an article in the Proceedings of the National Academy of Sciences, there's a puzzle: When men and women analyzed the same cartoons, different parts of their brains tended to light up on the fmri screen. This hints that for some unknown reason, male and female brains tend to process information about cartoons in different ways.

"There was no difference between males and females in any (humor-related) behavioral or performance parameter, except (the brains of) females reacted more quickly to cartoons that were not funny," Reiss told The Chronicle.

The deeper meaning of this finding remains unknown.

So far, scientists haven't drawn Earth-shattering conclusions from their brain-scans of cartoon-viewers and TV sitcom-watchers. True, in the resulting fmri images, the brains appear to be lighting up in some interesting ways, with noticeable differences between male and female brains. But for now, no one has a persuasive idea why, for example, Homer's declaration of "D'oh!" or Elaine's "yadda yadda yadda" or Bart's "Ay caramba!" or Jerry's "Hello, Newman" should make one part of anyone's brain glow while another part remains dark.

But researchers hope that continued scanning will offer some answers. As Berns half-jokingly suggested in his 2004 article, "Scientists have found the funny bone in the brain."