New research helps explain why crude comedy, even when including death or moral taboos such as bestiality, can make people laugh. Disgusting jokes can be perceived as funny so long as they somehow come off as benign, as not hurting anyone or anything, the study finds.

Scientists and philosophers, and of course comedians, have long sought the ingredients of humor. Several past theories attempting to explain humor have failed in one way or another, said A. Peter McGraw, of the University of Colorado-Boulder, who co-authored the study with Caleb Warren.

Those theories meant to explain narrow segments of humor, such as jokes, can't also explain broader humor across domains. For instance, theories underlying general humor would suggest we think things that are incongruous and release tension are funny. But unintentionally killing a loved one, while incongruous and an example of a release of aggressive tension, is unlikely to be funny, the researchers point out.

Now, scientists have come up with three criteria they find could explain why things are funny. McGraw and Warren figured the anecdote or scenario had to be incongruous (violate some moral or social norms, such as having sex with a dead chicken – an example given by the researchers), benign, and also reconcilable. In other words, there has to be some way to be disgusted by a moral violation and also consider it simultaneously benign.

What a hoot?!

The researchers tested their ideas, including ways in which an immoral or disgusting act could also be seen as benign, and hence, funny.

They presented various situations to volunteers they rewarded with candy bars. In one experiment supporting the idea that violation makes fun fodder, the volunteers read one of two versions of a scenario: one describing the company Jimmy Dean using a rabbi as spokesman for a new line of pork products; or one where Jimmy Dean hired a farmer as spokesman. Participants were more likely to laugh when reading the situation with a moral violation — having a rabbi promote pork — and to think it was "wrong" compared with the control version of the scenario.

In another experiment, participants read a scenario in which a man rubs his genitals against a kitten, with some participants reading a version in which the kitten "purrs and seems to enjoy the contact," while others read a version in which the kitten "whines and does not seem to enjoy the act."

Most participants, regardless of which scenario they read, judged the act to be both wrong (72 percent) and disgusting (94 percent). However, they were more amused by the harmless version (when the kitten enjoys the act) than the harmful one – 61 percent versus 28 percent, respectively. More than half of participants reported being both amused and disgusted in response to the benign setup compared with 22 percent who reported the same for the harmful scenario.

In the harmless scenario the man in the story violates a moral norm related to bestiality, the researchers explain. But since no one is harmed, the behavior is also acceptable according to a norm based on harm, leading to the chuckle.

Mental distance from a violation can also make that violation seem harmless. In another experiment, participants were primed to have a near or far psychological mindset by plotting Cartesian coordinate points either very close to one another or more spread out. Then participants read about a man either having sexual intercourse or marinating a chicken before cooking and eating it. Most participants thought the violation was disgusting.

However, those in distant-psychological group were more likely to think the sexual act was also amusing compared with the psychologically near group, 73 percent versus 39 percent, respectively.

From slapstick to serious comedy

McGraw thinks the humor rules could explain everything from puns and jokes to slapstick and other forms of comedy.

"We laugh when Moe hits Larry, because we know that Larry's not really being hurt," McGraw said, referring to humorous slapstick. "It's a violation of social norms. You don't hit people, especially a friend. But it's okay because it's not real."

He recalled an internet video of a chain-smoking Indonesian toddler as a possible example. "When I was first told about that, I laughed, because it seems unreal — what parent would let their kids smoke cigarettes? The fact that the situation seemed unbelievable made it benign," McGraw said. "Then when I saw the video of this kid smoking, it was no longer possible to laugh about it."

The findings could also explain why comedy films tend to have most success in their culture of origin.

"It's hard to find a comedy that's funny cross-culturally, because the ways that violations can be benign differ from culture to culture," McGraw said. "The comedy that is funny cross-culturally tends to involve a lot of physical humor. The violations are clear no matter who you are."

The research will be published in forthcoming issue of the journal Psychological Science.