Credit cards are a great convenience. They let us buy what we need even when we don’t have enough cash. They make it easy for us to shop online, buy meals, and rent cars when we travel. But credit cards also tempt us to spend more than we can afford.

Studies of consumer behavior show that people spend two to three times as much money when shopping with a credit card as they do when paying with cash.

The difference is in the level of impulse shopping. The act of paying with cash reminds us that we have a limited amount of money. We forget that limit—or ignore it—when we pay with a credit card.

When relying on cash, most people are disciplined in their buying and do a good job of ignoring the many impulse temptations they face. Because the cash is hard to part with, they take extra time to find the best bargains. When paying with a credit card, shoppers are much freer with their spending. They pick up those tempting extra items and add them to their carts. They also spend less time comparing prices and looking for bargains.

It goes even further. Credit cards free us to be more generous when shopping for gifts. They make us looser with our money when choosing food and drinks in a restaurant, and when leaving tips. And when we know we’ll be paying with plastic, we rarely buy just the one inexpensive item we were looking for. We add a couple of other things to the cart so we don’t look silly charging a small amount when we get to the front of the checkout line.