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The science of the gross-out comedy

Warner Bros.

We know, Ed Helms. We're shocked, too!

By Bill Briggs

We’re all grown-ups here.

Kind of.

So why have so many “Bridesmaids” viewers cringed with laughter while watching the bride (Maya Rudolph) and her girlfriends -- bedecked in designer dresses -- suddenly erupt in a food-poisoning-induced storm of vomit and diarrhea? (Pity that poor -- once-white -- wedding gown).

Why, in "The Hangover Part 2," will packs of theatergoers today simultaneously grimace and grin at the glimpse of a young man’s severed ring finger -- still wearing a Stanford class ring?

And why, in 2007's “Knocked Up,” did some of us wince and giggle when we saw a baby’s head crown from Katherine Heigl’s ladyparts as she screamed, “Get out!” to a horrified dude who had peeked into her birthing room?

Those scenes put the gag in -- well -- gag. But many of us roared despite our repulsion. What are we, like, 8 years old?

Why do disgusting or shocking movie moments still make some of us cackle till we cry?

According to two experts -- one a researcher, one a comic -- there’s psychology behind that crude comedy.

“Humor is elicited by the perception of something that seems to be unsettling, threatening, wrong, scary or anger-inducing,” said Peter McGraw, assistant professor of marketing and psychology at the University of Colorado, Boulder. “There’s a wonderful quote by Mark Twain that sums it up nicely: ‘The secret source of humor is not joy but sorrow. There is no humor in heaven.’ ”

Last August, McGraw co-authored a study examining why we laugh at images we consider to be morally wrong. By asking his test subjects to read offensive scenarios -- then tweaking those descriptions to see if the subjects still found them humorous -- the researchers developed their “benign violation theory.”

“Of course, things that are wrong usually make us upset. So at the same time that something is seen as a violation, it also has to be seen as benign -- that it is, in some way, OK or acceptable,” McGraw said.

That benign aspect is fueled, McGraw said, because the situation has “psychological distance” -- it’s happening to someone else, or it happened a long time ago, or that it’s so absurd, it seems obviously contrived. (This is where the old saying, "Tragedy plus time equals comedy," applies.)

Is there a demographic that seems most immune to insult and who, therefore, laughs harder at the raunchiest material?

“Young men seem to be pretty impossible to offend,” McGraw said. “As a result, a lot of things that everybody finds to be violations, they find to be benign violations.”

“It’s the frat humor,” agreed comedian Alonzo Bodden. “It all goes back to ‘Animal House’ and ‘Stripes.’

“When it’s done well, it’s funny,” Bodden said. “It’s funny because it’s so totally inappropriate.”

Bodden agrees with McGraw’s “benign violation theory.” But as a man who stands alone on stage seeking laughter, he also understands that what’s hilarious to one person, can just seem stupid to another.

“When it’s predictable or too over-the-top,” Bodden said, “when the (filmmaker or comedian feels they) have to make it so much wilder and more ridiculous, now it’s not funny anymore.”

To help draw his scientific conclusions, McGraw and his co-author, Caleb Warren, asked 36 participants to read the description of a violation. Some were aghast at the passage. But most were amused – because, to them, it seemed benign. 

The scene? A man rubs his genitals against a kitten -- which "purrs and seems to enjoy the contact."

See. Made you laugh. Well, some of you.

What's your favorite gross-out scene from a movie? Or -- can you think of a movie that went a little too far? Leave a comment telling us the movie and the scene.

Bill Briggs is a frequent contributor to msnbc.com and author of “The Third Miracle.”