Why does cash feel as if it disappears faster, even when you spend the same amount?

As you count out bills and take your change, you watch the money leave. When there are fewer bills and coins mixed in, even your fingertips can feel the difference.

A card is just as thick no matter how many times you use it. Payment is over the moment you insert or tap it, and you check how much you spent later as a number on a screen. So until you look at your statement in the evening, what you spent that day doesn't really stay with you. A debit card drains away as numbers on a screen too.

In 2001, Drazen Prelec and Duncan Simester at MIT auctioned tickets to a sold-out basketball game. Half the participants were told they'd pay in cash, and the rest were told they could pay only by card.

The average bid was about $28 on the cash side and about $61 on the card side, more than double. Payment was due by the next day, so installments or interest could hardly explain the gap. The researchers concluded that cards dull the pain of paying.

Many people assume card spending goes up only because of math like installments or interest. But as this experiment showed, the gap appeared even when the bill had to be paid right away. Even with the same amount, simply feeling the moment the money leaves less sharply can change how much you spend. When the bill is pushed to next month, the pleasure of buying and the pain of paying drift further apart, and what you spent on what can blur even more.

That doesn't make cards bad. They leave a record and spare you the change, which are real advantages.

If you mostly use cards, turning on payment alerts makes you see the amount the moment you spend it. Link a debit card to an account holding a set week's living expenses, and what's left becomes as visible as the thickness of a wallet. When choosing something expensive, ask yourself how much you'd pay if you were handing over cash. The point is to bring the moment the money leaves back in front of your eyes.