I think that both Matt and Kevin are right, although Matt did not defend   
his point in his initial post. The issue, it seems to me, is one of the   
evolution of fiat currency, not of its use. Kevin is right because   
children today learn to use their respective fiat currencies just as the   
capuchin monkeys did. The currency becomes a symbol to the individual   
that represents a projected consequence of using the currency.  
  
Matt is also right because monkeys did not invent fiat money. Humans   
did. And for them, the first users for the most part, and the second   
users almost certainly, associated liabilities with its use.  
  
This reasoning, by the way, is an application of the so-called   
regression theorem introduced by Mises. The means of introducing money   
are discussed by Mises at:  
http://www.econlib.org/library/Mises/msTContents.html  
See chapter 16.  
  
  
The reasoning of the regression theorem is also discussed by Mises.  
http://www.econlib.org/library/Mises/msTContents.html  
See Part 4.  
  
  
Pat Gunning