Soe Zeya Tun / Reuters

The most common gripes among moviegoers watching 3-D movies were that their eyes felt tired or they had a headache. But nearly 11 percent felt like they wanted to puke.

If you found yourself feeling a little woozy while watching 3-D films like "Avatar" or "Tron," you won't be surprised to hear this. More than half the people who put on the special glasses and caught a showing of a 3-D flick reported the movie made them feel sick to some degree, a new study suggests.

Roughly 55 percent of viewers had at least one physical complaint after the experience, according to research recently published in the journal PLoS ONE.

The most common gripes among moviegoers were that their eyes felt tired or they had a headache. But nearly 11 percent felt like they wanted to puke.

"I was surprised by the relatively high proportion of people who reported symptoms after a 3-D movie," said study author Angelo Solimini, Ph.D, an adjunct professor and research scientist in hygiene and public health at Sapienza University of Rome.

But there's no reason to shy away from a showing of movies like "Up" or the soon-to-be-released "Oz: The Great and Powerful." Solimini pointed out that viewer's symptoms were usually mild and seemed to disappear as soon as they took off their 3-D glasses -- except, perhaps if it triggered a headache.

Although Solimini has only seen one 3-D movie, "Despicable Me," he got the idea for this study after chatting with a group of parents. After taking their children to see a 3-D film, many of the mothers complained of physical discomforts, but their kids did not.

To look into these side effects, he rounded up 497 healthy adults in Italy, ages 18 to 65. Participants were asked to see one 2-D movie and one 3-D film during a three-week period. They could choose whichever movies they wanted as long as they didn't see the 2-D and 3-D flick on the same day.

Before and after seeing each flick, participants completed questionnaires about their movie-going experience, in which they rated their symptoms in three main areas: nausea, vision problems and dizziness.

Close to 55 percent of the viewers of the 3-D flick reported some level of sickness following the film compared to only 14% of those watching a 2-D film.

Nearly half of the 3-D viewers complained that the film hurt their eyes. It strained their eyes, blurred their vision, or made it hard to focus.

Slightly more than one in five 3-D moviegoers felt somewhat disoriented at the theater. They had a headache, or felt off-balance or dizzy, whether their eyes were open or shut.

About one in 10 3-D film attendees felt queasy during the show.

Some individuals were more prone to these unpleasant feelings than others. The study found that women, especially those with a history of car sickness, vertigo, or frequent headache, may be more vulnerable to these symptoms.

As for why some people find it harder to handle 3-D movies than others do, Solimini suggests it's because the distance at which our eyes converge is different from where they focus. This mismatch causes extra work for the visual system that for some individuals may result in these annoying side effects.

The most susceptible people, he explains, are those with unequal vision in both eyes or those with small vision misalignments.

Solimini draws an analogy between seeing a 3-D film and riding a roller coaster. Both are forms of entertainment in which some people may be willing to put up with an increase in symptoms and mild -- but temporary -- discomfort as part of the experience. 

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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.”

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