Déjà vu?

A psychology exam at an American university concluded with this question -
"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 to the rest of the class, only I will see the responses."
The setter said he has been including this final question since 2008, and only once had less than 10% of students opted for 6 points.  He said his objective was to teach students that "if too many people overuse a common resource then everyone in the group suffers, not just the selfish ones".  But what immediately struck me was that this is simply a slightly different slant on the Prisoner's Dilemma - see the series of posts in December 2011.