No matter how you feel about TikTok, you must admit it can get us thinking. #GirlMath (or #GirlMaths if you’re Down Under or Across the Pond) went viral when it spoofed the ways women supposedly play mind games about spending.

Why Did Girl Math Become a Trend?

Girl Math is enough to make a feminist’s blood curdle (to be clear, there’s also Boy Math and even Corporate Math, although those memes don’t focus so much on shopping). 

But Girl Math is also, well, funny. And it hit a nerve. The trend likely went viral because it addresses, in the way only social media can, the psychology of spending and how very weird that can be. One thing is clear to anyone, girl or boy, who’s struggled to make a budget and stick with it: When it comes to money, it’s all too easy to play those kinds of mind games.

Read More: Why Do We Make Bad Shopping Decisions?

What Is Girl Math?

It’s easier to explain girl math by taking a look at a couple of examples.

• Returning an item, then thinking you can spend the refund money. It had already come out of your account, so now it seems like new money going in. 

• Spending an extra $25 on things you didn’t want, just so you don’t have to pay $5 shipping. 

• Thinking that if you pay for something in cash, it doesn’t count as spending because there’s no record of it. 

• Doing your Christmas shopping in the summer, then in December feeling like you didn’t spend any money on Christmas gifts.

• Purchasing an item at a discount price, then buying something else with the savings and considering the second purchase free. 

• Driving 25 miles out of your way to pay a few cents less for gas.

Read More: Why We Buy Weird Things in Times of Crisis

The Psychology of Spending Money

But it works both ways. If we have all these crazy mind tricks to make ourselves feel better about spending, we can use similar strategies to help control our spending. Johanna Peetz is a psychology professor at Carleton University in Ottawa, Ontario, who studies personal spending and self-regulation strategies.

How to Stop Spending Money

Based on her own research and input from research participants, Peetz makes a few suggestions on how to stop spending money on unnecessary things:

• Make it difficult to make impulse purchases online by deleting your credit card information from websites. If you have to rekey the info each time you want to make a purchase, you’ll have a little time to cool off and make sure you really want to spend that money.

• You can give yourself some cooling-off time for in-person purchases as well, Peetz says. Reserve an item you want to buy rather than purchasing it immediately. If you don’t think it’s worth going to the store again the next day, you probably shouldn’t buy it. 

• Getting an idea of the real cost of an item can help, too. Peetz suggests calculating how long you’ll have to work to pay for the item. An expensive new sofa might seem like a great idea until you realize that paying for it will cost two weeks of work.

Is Marketing Just Manipulation?

But be forewarned: You’re up against a formidable opponent. “The problem is,” says Peetz, “there’s a huge industry dedicated to making people spend.” She adds that the industry doesn’t consider how spending affects people’s happiness, just how to get more money from them. “The consumer has to work against all this advertising and all the tricky ways the industry tries to get your money. It’s almost like an arms race.”

But still, Peetz doesn’t want to suggest that spending = bad, Scrooge = good. Research has shown that spending, when done right, can actually improve happiness, she says.

Read More: Is a Shopping Addiction Real?

Does Money Buy Happiness?

Much of this research has been done by Michael Norton at Harvard University and Elizabeth Dunn at the University of British Columbia. They’re the authors of Happy Money: The Science of Smarter Spending, a book arguing that spending money in the right way can actually enhance happiness.

Norton’s and Dunn’s research has shown that spending money on other people actually makes us happier than spending it on ourselves. Simply buying someone a coffee or giving $5 to a homeless person can have a bigger effect on our overall happiness than buying something for ourselves, says Norton.

Why Does Spending Money Feel Good?

Norton also says money can make you happier if you spend it on experiences rather than stuff. “I play the guitar,” says Norton. “I know some people who buy guitars to put them on their wall as kind of a possession. Other people who buy guitars buy them because they’re going to play the guitar.” In both cases, the person bought an object. But the person who bought the guitar to play — or learn to play — is purchasing an experience.

Both Peetz and Norton point out that all this applies only to people who have some extra money to spend. For many, the problem is that they don’t have enough, even for the basics. Mind games to justify discretionary spending aren’t even an option for them.

Read More: A Neuroscientist Explains Why It’s Better to Give Than to Receive