When is it okay to joke about a tragedy? New research shows that a comedian must carefully balance how bad and how distant an unfortunate event is to make a joke about it that won't leave an audience stone-faced or shouting, "Too soon!"

Researchers from the Humor Research Lab (HuRL) at the University of Colorado Boulder conducted several studies to explore how psychological distance and severity impact humor about an unlucky turn of events.

In the first study, participants in an online survey were asked to describe a personal experience that became either less funny or funnier as time passed, and then to rate its severity. The events that became funnier over time generally were rated as more severe than the events that lost their humor, the researchers found. They labeled these serious but distant events "benign violations."

Similarly, in a second survey, participants tended to rate a grave event, such as being hit by a car, as funnier if it happened five years ago. Meanwhile, the researchers found that a minor event, such as stubbing a toe, was perceived as funnier if it happened the day before, according to a statement from the Association for Psychological Science, which published the study in its journal Psychological Science.

In another study, undergraduates were asked to read Facebook status updates from strangers and friends, who posted about accidentally donating money via text message. The students said that a stranger accidentally donating $1,880 was funnier than a friend doing so. However, the participants said a friend making a $50 donation was funnier than a stranger making the same mistake.

"These findings suggest that there's a real sweet spot in comedy – you have to get the right mix between how bad something is and how distant it is in order for it to be seen as a benign violation," Peter McGraw, who runs HuRL, said in a statement.

"Having some distance from tragedy helps to create a benign violation, which facilitates comedy. But when you become too distant from a mild violation, it's just not funny anymore," McGraw added.

Follow LiveScience on Twitter@livescience. We're also onFacebook &Google+.

• 7 Things That Will Make You Happy
• 10 Things You Didn't Know About You
• 7 Thoughts That Are Bad For You