Bizarre social experiments in the classroom are often the stuff of urban legends and nothing more, but one University of Maryland professor decided to give his students a real life lesson they (and we) could not possibly forget. And their grades suffered as a result -- well, sort of.

Psychology professor Dylan Selterman introduced his pupils to the concept of the "Tragedy of the Commons" -- an ethical observation that human beings usually take more than an equal or sustainable share of a public good, thereby ultimately destroying it for everyone.

It's most often used in the environmental context, because obviously, but Professor Selterman presented it like so:

The text reads: "Here you have the opportunity to earn some extra credit on your final paper grade. Select whether you want 2 points or 6 points added onto your final paper grade. But there's a small catch: if more than 10% of the class selects 6 points, then no one gets any points. Your responses will be anonymous for the rest of the class, only I will see the responses."

Simple enough, right? Everyone -- or at least 90% of the class -- picks "2 points" so everyone gets at least some points. But in reality? That's... not what happens.

According to Selterman, about 20 percent of the class chose six points. Which means no bonus points for anyone. BOO.

In an article for the Washington Post, Selterman wrote that this happens almost every stinking time he gives the challenge, and he's got some theories as to why it is that kids can't resist the siren song of six.

"This exercise impels students to consider how their actions affect others, and vice versa," he wrote. "I’ve been giving it to students since 2008, and only one class has successfully mastered the challenge. In all other classes, more than 10 percent chose 6 points. Students’ temptation to reach for more points is very strong.

"It feels good to be cooperative both from a strategic and moral perspective. After all, if every student chose 2 points, everyone would get the extra credit, thus making it a rational choice," Selterman continued. "But many students choose the seemingly selfish option. Why? Perhaps to increase their own grades, or perhaps because they fear that they will be taken advantage of. No one wants to be the chump that chooses fewer points when they could have had more."

Of course, this is not a new development for mankind, and it's certainly not a problem shared by just the current crop of college students either.

In fact, Selterman told USA Today that he first heard of the experiment back when he was at college.

"Some have asked me if today’s college students are more prone to self-interested behavior. I don’t think that’s the case," he said. "The temptation to be self-serving in these situations is not new. Communities have been grappling with the commons dilemma for centuries."

But by introducing his students to the concept of sharing and caring, Selterman hopes it'll make a difference.

"When people leave my classroom, I want them to realize they have the tools to change the world for the better, and to help usher us into a more enlightened society," he wrote.

And it looks like Selterman is in good company with his tutorial, too.