Why grubby notes may slip through your fingers faster.

When I popped a few notes into a card for my niece this Christmas I made sure the notes were new and crisp, rather than crumpled grubby ones.

Why should that matter, I wondered.

Surely a tenner is still worth ten pounds, whether the note is freshly minted or has been through a hundred hands. Or is it? New research from the University of Guelph** shows that not all notes are created equal, and we’ll cherish new ones over grubby ones any time.

I wouldn’t give my niece a dirty note just as I wouldn’t give her a pair of pre-worn socks.

In five different studies, the Guelph researchers gave people old or new notes to spend (bet they didn’t have trouble finding participants for that study). People spent more and took more chances with older, worn money. Each time the same main reason emerged: people don’t like "dirty money."

Apparently it's the 'ick' factor: the idea of touching something that others have handled. People want to rid themselves of worn currency, fearing the contamination from others.

People value a crisp new note because they take pride in it, almost viewing it as a reflection of themselves. So, when spending around others, we are more likely to hand over our new-looking currency, even if we have to use four £5 notes rather than one crumpled £20 note. It's about social currency. If the transaction has no social value you'll get rid of your old notes. But when spending (or giving) to impress you want your notes to spell 'clean'.

I wouldn’t give my niece a dirty note just as I wouldn’t give her a pair of pre-worn socks. This challenges the long-held belief that we take money at face value - it’s actually subject to the same inferences and biases as the products it can buy.

**Fabrizio Di Muro and Theodore J. Noseworthy. Money Isn’t Everything, but It Helps If It Doesn’t Look Used: How the Physical Appearance of Money Influences Spending. Journal of Consumer Research, April 2013