Game Theory?

A few weeks ago when I was at a party on campus, the party just so happened to be running out of "soda."  My friend and also owner of the house quickly began taking up a collection to buy some new soda.  He was having a rough time getting people to donate to the pot so he thought it was a good idea to put a twenty dollar bill in the large, clear, glass cup.  I asked him what is the point in doing that?  I thought that if everyone sees the twenty dollar bill in there, then they will feel as if we have gathered enough money to make another soda run.  However, he claimed that if people saw the twenty dollar bill in there then they would be willing or at least feel as if they could pay up with some cash.  It did not really make too much sense to me at the time.  A few days back when we had the extra credit assignment in Arps Hall, the game in which people could add to the group pot even though it was in their best interest to keep the money for themselves reminded me of this situation.  The people at the party played as the students who could add to the pot or be a bunch of jerks and keep their money.  As the game showed, people added to the pot when they could see what the maximum contribution was.  My friend's idea worked as people added to the pot at the party.  In one game that we did in Arps, once money was added to the pot their was no way of getting it back.  This game also reminded me of the party because once people added to the pot their was no way they were getting their money back!  I am not really sure what this theory is called, maybe Game Theory, sorry Kyle, but I do like it since it is a easily carries over into my real life just about every weekend.