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Why I give my students a ‘tragedy of the commons’ extra credit challenge

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Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#51

Post by tolmasky »

fcbrooklyn wrote: post #33

Actually, I think in this case the only rational choice is to ask for the 6 points. One of two things will happen: 1) Less than 10% will follow suit, in which case you'll get a 6 point boost, and you'll have secured an advantage over 90% of your classmates. 2) More than 10% will follow suit, and noone will get anything, in which case you will have no advantage over your classmates, and neither will any classmate have…

A lot of people are commenting on how the article said there would be no curve, but I interpreted your statement to mean a deeper comparison to other students: the intrinsic value of doing better or worse than them, that translates to actual physical results: better chance at valedictorian than them, better chance to stand out to the teacher, higher overall GPA, etc.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#52

Post by gorena »

edwardy20 wrote: post #40
fcbrooklyn wrote: post #33

Actually, I think in this case the only rational choice is to ask for the 6 points. One of two things will happen: 1) Less than 10% will follow suit, in which case you'll get a 6 point boost, and you'll have secured an advantage over 90% of your classmates. 2) More than 10% will follow suit, and noone will get anything, in which case you will have no advantage over your classmates, and neither will any classmate have…

> Because the "points" have no intrinsic value except in comparison to your classmates This is where your logic is wrong. The professor is not saying the class is graded on a relative scale (for example, top 10% of the class gets As). If everyone gets two points, and it bumps up everyone's GPAs, then of course it will benefit them all, especially in comparison to people who are not in the class.

This is not necessarily true. If you're already a good student, this devalues your GPA, mostly due to the generally awful GPA system. Assuming your school considers everything above a 92 to be a "4.0", if you're already in that range, you definitely don't want to help anyone else into that range.

Note that, of course, this would be fixed by just making GPAs decimal numbers out of 100, the average of all of your actual, numeric grades from each course (multiplied by credit hours?). You can divide it by 25 if you really want the weird 4.0 scale for some reason.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#53

Post by bsder »

This really doesn't work for me as an experiment.

10% is too easy to hit. Do 3 or more students need the 6 rather than the 2? Why should I choose the 2 if it won't do me any good?

In any class I teach, there are generally 10% on the line between grades that requires that I take into account a little more than just scores. Did they do all the homework? Did they improve on assignments or were they blowing them off? etc.

Given that 10% probably need the 6 and not the 2, this is likely to never work.

I had a tragedy of the commons that I hadn't intended. I had an extra credit programming assignment, but there was a catch--the students had to write the tests for the automated tester. If nobody wrote tests, nobody had the chance to get any extra credit. They were allowed to collaborate on the tests, but not the solution.

Everybody complained bitterly when nobody wrote tests.

My response was not terribly charitable: "This is extra credit, folks. Not charity. You all had two options.

First, write the tests yourself. Yes, writing tests is time consuming, but not horribly difficult. Some students started, realized the amount of work, and stopped. However, once somebody writes the tests, everybody get to benefit.

Second, encourage someone else to write the tests for you. Did any of you talk to the students most likely to write tests? Did any of you encourage these students to put in the work if you couldn't pull it off yourself? Did any of you offer to compensate them for their valuable time?

Many of you have been repeatedly asking for a group assignment since the beginning of the semester. THIS WAS A GROUP ASSIGNMENT AND YOU FAILED. It simply worked out that freeloaders weren't guaranteed to be carried by the best students. The best students realized the amount of work and simply opted out since they already had enough points.

Welcome to the real world. Figuring out how to get someone to do something that they don't really want to do is a fundamental problem of life."

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#54

Post by lifeformed »

fcbrooklyn wrote: post #33

Actually, I think in this case the only rational choice is to ask for the 6 points. One of two things will happen: 1) Less than 10% will follow suit, in which case you'll get a 6 point boost, and you'll have secured an advantage over 90% of your classmates. 2) More than 10% will follow suit, and noone will get anything, in which case you will have no advantage over your classmates, and neither will any classmate have…

I think it also depends on the class size. If there are only 10 students, then it's very risky to pick 6 points, since you have to be the only one who picks it. But if there are 1,000 students, then it'd make perfect sense to pick 6 points. Basically, the less of an effect your own decision has on the group outcome, the more rational it is to pick the selfish decision.

This is why I find voting hard to justify if you view it pragmatically (even though I do it). It's mathematically improbable that my vote will make any difference. Then why do it? Sure, if everyone thought that, it would be bad. But it doesn't matter what other people do: your vote still won't matter either way. It's such a huge pool of voters that it's literally impossible to put yourself in a position where your vote makes a difference. Basically, it's important that people vote. But it's not important that a particular person votes.

Can anyone convince me why I in particular should vote in an election of a quarter billion people? Are there any reasons other than following idealistic principles? I mean, following principles is important, but I was wondering if there are more pragmatic arguments.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#55

Post by Tossrock »

It's funny how many people are saying "oh just get everyone organized and have a lottery/auction". Yes, if we could perfectly organize large groups of people we could solve the tragedy of the commons. Unfortunately, organizing large groups of people is hard.

Even in the scenario where everyone is a rational actor (ie, fantasyland), effectively communicating to a group of > 20 people and obtaining unanimous consent is an exceedingly difficult problem.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#56

Post by jedmeyers »

ryan-c wrote: post #43
jedmeyers wrote: post #27

Get together, auction the 6 point slots. Then, depending on whether it works or not, either evenly distribute proceeds to everyone or return the money to the auction winners.

Or more generally allocate the 6 point slots in advance - how they're allocated doesn't really matter. The point is that everyone knows that if they are supposed to choose 2 points and instead choose 6, nobody gets anything. Someone still might blow it for everyone out of spite, though.

By involving the auction you are adding an additional incentive to not blow it for everyone - you are getting money from the person who will get higher extra grade than you.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#57

Post by tolmasky »

I'm surprised no rich student ever just offered ahead of the tally that they'd pay everyone $x if no one choose 6, where x is more valuable than 4 points. He now has the ability to safely choose 6, and everyone else is paid for their cooperation.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#59

Post by gorena »

bduerst wrote: post #48
fcbrooklyn wrote: post #33

Actually, I think in this case the only rational choice is to ask for the 6 points. One of two things will happen: 1) Less than 10% will follow suit, in which case you'll get a 6 point boost, and you'll have secured an advantage over 90% of your classmates. 2) More than 10% will follow suit, and noone will get anything, in which case you will have no advantage over your classmates, and neither will any classmate have…

From the article, the class isn't graded on a curve so your assumption that 2 points is worthless doesn't apply.

This assumes you haven't already maxed out the GPA value for the course. If you already have a 92 (I went to a school that didn't have "A+", YMMV), there's no reason to increase your grades, and anyone else increasing their grade has the potential to devalue yours.

Note that this is fixed by just averaging your actual grades out of 100 to form your GPA, instead of mapping from a 0-100 range to an enumeration to a 0-4 scale then averaging the results.

Re: Why I give my students a ‘tragedy of the commons’ extra credit challenge

#60

Post by bduerst »

Tossrock wrote: post #55

It's funny how many people are saying "oh just get everyone organized and have a lottery/auction". Yes, if we could perfectly organize large groups of people we could solve the tragedy of the commons. Unfortunately, organizing large groups of people is hard. Even in the scenario where everyone is a rational actor (ie, fantasyland), effectively communicating to a group of > 20 people and obtaining unanimous consent is…

The anonymous nature of this removes the reputation cost for picking the six points.

Collusion isn't possible because there is no penalty for breaking an agreement, and the signals it creates (everyone is picking 2) only makes rationally self-motivated individuals more likely to break it.

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