Researchers found we spend old or filthy bank-notes more freely than freshly-minted ones.
Professors Fabrizio Di Muro and Theodore Noseworthy said dirty and clean bank-notes evoke feelings of disgust and pride in equal measure.
They said: The physical appearance of money can alter spending behaviour. Consumers tend to infer that worn bills are used and contaminated, whereas crisp bills give them a sense of pride in owning bills that can be spent around others.
Prof Di Muro, of Winnipeg University, and Prof Noseworthy, of Guelph University in Ontario, said we don't like the idea of touching something countless other people have also handled.
This is magnified when a bank-note is dirty, worn or crumpled because we can see evidence this cash has passed through a lot of hands before getting to ours, they said.
The researchers added: Consumers may value a crisp banknote more than a worn bank-note because they believe the latter is disgusting and thus want to be rid of it.
In several studies consumers were given either crisp or worn bills and asked to complete a series of tasks related to shopping.
They tended to spend more with worn bills than with crisp bills. They were also more likely to break a worn larger bill than pay the exact amount in crisp lower denominations.
However, when consumers thought they were being socially monitored, they tended to spend crisp bills more than worn bills.
The researchers said: Money may be as much a vehicle for social utility as it is for economic utility.
We tend to regard currency as a means to consumption and not as a product itself, but money is actually subject to the same inferences and biases as the products it can buy.
Prof Di Muro and Prof Noseworthy said their study published in the Journal of Consumer Research shows we're proud to be in possession of new, crisp currency.
Even though it's just money we value it more when it's nice and clean because it makes us feel proud to have it - especially if we're in a social setting where other people might see the bills, the researchers said.
This could mean that asking a bank cashier for newer notes could in fact help curb spending, they said.
