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Sat 02 September 2023:

These shoes are perfect, made for me! I have to get them! But really, I should be paying off my car loan instead. I can’t justify this purchase. Or can I …?

We all know this feeling, this tension between what you really want to do and what you really should, or shouldn’t, do. What you are experiencing is cognitive dissonance.

It’s a psychological discomfort we feel when our behaviours and our values or beliefs do not match. Not to worry, we can make that discomfort simply disappear with a good dose of #GirlMaths!

Free Woman Carrying Tote Bags Stock Photo

So what is #GirlMaths?

GirlMaths recently became a viral phenomenon on TikTok after New Zealand FVHZM radio hosts Fletch, Vaughan and Hayley used #GirlMaths to justify one host’s mother’s expensive dress purchase as basically free because the dress was going to be worn at least four times.

@fvhzm Using #girlmath to make an Italian silk dress basically free 🫡🇮🇹 Let us know if you need help justifying your spending 🫶 #itsbasicallyfree ♬ original sound – FVHZM

Since then, influencers have added to the #GirlMaths trend with gems such as “If I buy it for $100, wear it, and then resell it for $80 then I basically wore it for free”, “If I pay with cash, it means it’s free”, and “If I just returned something, then purchase something new for the same amount of money, then it’s free”.

The reason #GirlMaths resonates so well with everyone and allows it to go viral is that we are very familiar with this type of thinking. The mental gymnastics of #GirlMaths needed to justify cost-per-wear or cash-is-free is a perfect display of behavioural biases and heuristics, such as confirmation bias and denomination bias, being applied to everyday consumption decisions.

The psychology of decision-making

Behavioural biases and heuristics are shortcuts in our thinking that help us make decisions quicker and easier, and are great for reducing the cognitive dissonance we sometimes experience.

Our brain has a lot of decisions to make in a day and simply doesn’t have the power to scrutinise every little detail of every decision. These shortcuts in our thinking may facilitate the decision making process, but they don’t always mean we make the most optimal decisions.

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Confirmation bias is a bias where you justify your decisions by considering only the evidence that supports what you want and ignore the evidence that would mean you’d have to make a different decision. Cost-per-wear does sound quite financially savvy. It is just like bulk-buying pantry essentials, right?

The issue is you are ignoring the facts such as: 1) your disposable income does not match this expense in light of your utility bills, 2) you could rewear a cheaper dress all the same, and 3) by spending money on a fancy dress, you lose the opportunity to spend the money on other better investments for wealth accumulation, or to pay off your car loan.

Free Woman Wearing a Brown Dress Carrying Shopping Bags Stock Photo

The financial and social costs

But it’s all a bit of innocent fun, right? Surely people won’t take #GirlMaths that seriously? We beg to differ.

First, the term is unnecessarily gendered. Gendered language operates to reinforce societal expectations with a particular gender and can promote stereotypes, biases and binary categories.

In this case, the term “girl maths” reinforces problematic stereotypes that equate women with consumption, frivolity and extravagant spending. When stereotypes are reinforced within our own social circles, we are more likely to internalise these as part of our identity.

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By representing women in a less favourable way, the term operates to both demean and discriminate on a gendered basis. This is heightened by the use of “girl” as opposed to “woman”, which implies someone is childlike or lacking in knowledge or experience. It also begs the question what “boy maths” – set up as something opposing and different – might connote.

Second, the #GirlMaths trend reminds us of the power of “finfluencers” – social media content creators amassing huge online followings by sharing advice on anything from budgeting to buying a house, to investing.

These online gurus appeal to Gen Z and millennials, simplifying complex financial concepts into digestible nuggets, much like #GirlMaths simplifies purchases based on cost-per-wear or cash-as-free.

Free Happy woman shopping online at home Stock Photo

Just as regulators such as ASIC repeatedly warn us of the dangers of buy-now-pay-later services, we must caution the #GirlMaths trend as a dangerous cocktail for young women who are susceptible to the “advice” of finfluencers.

The trend resembles BNPL by breaking down expenses into smaller, more palatable portions, making purchases seem justifiable and affordable at the moment.

Denomination bias describes this tendency to spend more money when it is denominated in small amounts rather than large amounts. We find it much easier to spend $50 four times than $200 all at once.

However, the convenience of these shortcuts in our thinking can obscure the hidden financial risks. You may overlook the bigger picture of your financial health, and spend more than what you can afford. That’s why a large number of BNPL users find themselves ending up in a modern debt trap.

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The perils of #GirlMaths

The danger of #GirlMaths to young women lies in the cocktail of feeling oddly familiar and reinforced in this biased thinking, the problematic stereotypes that shape identities, and the power of finfluencers, who wield increasing influence over the financial choices and decision-making of young women.

While the term may initially come across as innocent fun, it’s crucial not to underestimate its potential harms. Instead, let’s champion the use of inclusive language in finance that doesn’t perpetuate gender biases.

And if you’re a staunch supporter of #GirlMaths, we strongly urge you to take into account the possible adverse financial consequences of these quick-fix spending habits.


Janneke Blijlevens

Senior Lecturer in Marketing, RMIT University

I am a Senior Lecturer in the Marketing Discipline and currently teach Interactive Marketing, and Principles of Social Impact. I am a founder member and former director of the RMIT Behavioural Business Lab and I manage the Bachelor in Business Major in Social Impact. With a Masters in Psychology, a PhD in design and consumer behaviour, and work experience in both design and business schools my research is truly interdisciplinary. I have extensive experience in using design thinking to uncover behavioural drivers to understand why people make certain decisions and uses this ability to design behavioural interventions that help people make better decisions for themselves and society. I have led multiple research projects delivering on behavioural insights and designed behavioural interventions, with many having gained world-wide attention and generating impactful outcomes including evidence-based, socially responsible recommendations implemented in sectors such as energy, finance, and community service. I am also a regular contributor in written, radio and TV media commenting on consumer decision making, behavioural insights, and the design of behavioural interventions and policy.


Angel Zhong

Associate Professor of Finance, RMIT University

Angel Zhong is an Associate Professor of Finance at RMIT University. She specialises in asset pricing and investor behaviour in financial markets, with a strong focus on the equity market. Her research is at the forefront of the development of the Fama-French asset pricing model in the Australian market. She has also undertaken research in the difference in behaviour of institutional investors and retail investors on stock markets around the world. She is an aspiring academic with strong ties to the industry. Her research has strong investment applications for investors. In addition to academic research, she regularly undertakes applied research and is a successful recipient of grants in the area of measuring mispricing and sentiment in the Australian equity market. Angel remains engaged with external stakeholders while undertaking her academic responsibilities. Her research has frequently attracted media interest, including TV interview on ABC and SBS, regular interviews on Ausbiz, radio interview on ABC, coverage in the Age and the Australian Financial Review.


Lauren Gurrieri

Associate Professor in Marketing, RMIT University

Dr Lauren Gurrieri is a marketing academic whose research examines gender, consumption and the marketplace with a focus on gender-based inequalities in consumer culture.

This includes how women can be stigmatized, stereotyped and excluded in marketing; issues of body idealisation, objectification and violent representations in marketing; and the strategies used by female consumers to resist and challenge marketplace norms.

Her most recent research investigates these issues in digital culture in the form of Instagram influencers.

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