the above link is to a yahoo article titled: 'Dirty' Money Affects Spending Behavior, Study Finds.
According to the study, people are more likely to spend dirty or crumpled money than fresh new money. (Personally I think that is a load of crap, but whatever).
At the bottom they explained how they completed the study. In summary, they gave participants an anagram. If the participants solved it, they received either a crumpled up $10 or a fresh one. Then they were told that they could do another anagram if they bet their current $10. If they solved the anagram they would win $20 (which was shown to them and was again, either new or crumbled).
According to the results, people with a crumpled $10 who were offered the new $20 if they won gambled more often than those with a fresh $10 or who were offered a crumpled $20.
However, when I went to the actual study (http://http://www.jcr-admin.org/files/pressPDFs/100312163624_Noseworthy_Article.pdf) there was more to it than that, including a feeling of pride, where people were more likely to spend a new bill in the presence of others, but save it when alone.
A little bit about the study: Participants were undergraduates from the University of Winnipeg. There were two studies. One, the above gambling study, and the one mentioned below.
Undergraduates were offered $20 for participation in this study. Once in the study, they were offered wallets with a total of $20 in it, divided into a $10, a $5, two $2, and a $1. They were randomly assorted into groups that had crumpled bills and groups that had crisp bills. All of the bills were new.
In total, all results showed that people are more likely to save new crisp bills, and spend crumpled ones. Okay, now I will admit, it sounds a bit more likely. But still, there is definitely the problem of the fact that the study only tested on Undergrads...seriously, can you draw many conclusions about the entire population from a group of college students looking for easy money? Answer: definitely not.
Also, in the age where the majority of us use debit and credit cards, I foresee bills becoming (and this study) eventually becoming obsolete.