You know the situation. Class was supposed to start 10 minutes ago, but the professor has yet to show. You're antsy. You've got better things to do than sit around for a tardy instructor, you think.

People start to leave. One student says to another as they both walk out, "Yeah, if the professor doesn't show up after the first 10 minutes, you can just leave. It's a rule or something."

"Really?" says the other student. "I always thought it was 20 minutes."

Yeah, you've heard this too, you think. So you compromise: At a quarter after, you bolt.

The Waiting Rule

Wishful thinking. That's what many folklorists say about the "rule." Fact is, there's no such thing. Never was one.

Nevertheless, the belief that such a rule exists has spread, and rarely is a college or university exempt from the myth in one form or another. In fact, "The Obligatory Wait," as University of Utah professor Jan Harold Brunvand calls it in his book The Baby Train, is just one of many such legends that are spread throughout society.

In some versions of "The Wait," the length of time varies with an instructor's rank. Jim Griffith, the coordinator of the Southwest Folklore Center at the University of Arizona, explains, "Sometimes, it can get pretty elaborate - five minutes for a lecturer, 10 minutes for an assistant professor and 20 minutes for a full professor. If it's a department head you wait until the next class."

However, Brunvand notes in his book that "As far as I know, a waiting rule for late professors has never been made an official regulation by a college administration."

So if these rules don't exist, why are they so widely believed? Many folklorists say the myths are spread as truth, because those who believe them wish they were true. After all, who wouldn't trust the words of the omnipotent "friend of a friend?"

"I think (the myths) serve a function, each one," Griffith says. "If you're sitting around the classroom, and the teacher doesn't show up, you're in sort of a bind. Can I leave? Am I going to get punished if I do leave? Suppose he walks in and gives a quiz?

"It's really comforting to have a set of rules, so somebody created those rules."

James Uhrig, senior library assistant at the UA Main Library, says he remembers the "waiting rule" from his days as an undergraduate at the UA in the early 1970s.

"That was something I heard people say in classes that I had," Uhrig says. "In fact, there were a couple of occasions where we waited that period of time and the teacher didn't show up and we left.

"In the '70s it was like if someone had heard something that they heard in good faith to be true, and they acted on that, that was sort of allowed. It was like, oh well."

Some things never change.

The Automatic 4.0

Fact: If your roommate commits suicide, the university automatically awards you a 4.0 for that semester.

Just kidding.

Griffith says as far as he knows, the "automatic 4.0" myth started in the middle 1980s, but that "when I first heard it, it was at least a B average. Now it's gone up to a 4.0. That's great."

Many folklorists believe that these myths reflect society's values - in this case, getting good grades is the anxiety du jour. Griffith, who attended the UA in the 1950s, says contemporary myths are merely a sign of the times.

"In my day, student suicide? Aw, come on," he says. "The pressures just weren't on us in the '50s and '60s. Now it's something real. People's roommates do commit suicide, so this belief has grown.

"Folklore tends to serve a purpose, and when it no longer serves a purpose, it goes away."

On the Internet, the story is alive and well. There are several newsgroups devoted to the subsets of urban myths, including alt.folklore.college. Messages regarding the "automatic 4.0" usually are along the lines of: "Really? At my school it's only a 3.5."

The variations are a tall tale's tell-tale sign. For his Humanities 420 class, Dave Albert, 23, biochemistry senior, did a paper on college myths. For the assignment, he gave surveys to students asking them if they knew of the listed legends and if so, if there were any changes between the legends they heard and the ones listed.

Of the 16 surveys returned, 10 people said they had heard of the "automatic 4.0," and three people elaborated. The most technical response was, "They add the 4.0 to your cumulative GPA. However, you do not receive the credits necessary for graduation." The others were: "I heard this with regard to ASU - but was told the policy was university specific;" and, "If your roommate dies (for whatever reason) you get a 4.0 for the semester."

Albert says the rule has "too many holes" to be true. Imagine that.

The Roommate Murder

If you scare easily, do not read on. However, it you were ever a freshman and you're female, you probably heard these stories anyway.

There are many variations regarding the "roommate murder," but one of the most popular ones go like this: Two female roommates share a dorm room; one goes to the library while the other sleeps; the former runs back later because she forgot something, leaves the room without turning on the light, and goes back to study. Hours later, she returns to find her roommate murdered and a note on the mirror written in blood, "Aren't you glad you didn't turn on the light?"

Jessica Armistead, 19, a theater arts freshman and a resident of Yavapai Hall, told the above version and a different one which had the first roommate going to a party. Her roommate, who was in the room and had never heard the stories before, then had Armistead "check under the bed."

"I started walking out the door and she started shaking," she says, laughing. "But I guess that's the purpose of these stories."

Not surprisingly, other residents of the hall had heard either the same story or variations upon the theme. Two said the note read, "Aren't you glad you didn't turn on the light, bitch?"

"I heard a slightly different version my freshman year and the people that told me said it was true," says Jamie Davis, 19, chemical engineering sophomore. "I thought that it had actually happened here at the University of Arizona, but I had a friend at NAU say, 'I heard the same story too.'"

However, some folklorists offer a word of warning: If you're planning on rushing home from class to frame your roommate's suicide so you can get straight A's, better wait to see if that professor shows up.

After all, you wouldn't want to miss class.

You can find the frequently asked questions list of college myths and legends at http://osnome.che.wisc.edu/~palou/afcFAQ. Also check out http://cathouse.org/urbanlegends/afufaq.