Why Does Impulse Buying Happen in a Sale and Not at Full Price?

Impulse buying in a sale: a 2025 study found the same headphones felt worth $17.35 or $18.89 depending only on where the old price sat.

Gizella Nagyne Palinkas

10/25/20268 min read

The short answer

Impulse buying happens in a sale and not at full price because a discount does not only change the price — it changes what you believe the thing is worth. In a 2025 experiment, people shown the same pair of headphones estimated a fair price of 18.89**whentheregularpricesattotheleftofthediscount,and**17.35 when the discount sat on the left instead. Nothing about the product changed. Only the arrangement of two numbers did.

That is the whole mechanism in one sentence: the seller supplies the number you compare against, and you compare against it.

What's happening psychologically

When you judge whether something is expensive, you do not weigh it against your income or against its usefulness. You weigh it against a reference price — an internal "this is roughly what this costs" figure. That figure feels like your own opinion. It is mostly assembled from whatever numbers you have recently seen.

A discount hands you a reference price for free. "$40, now $28" does not read as "costs $28". It reads as "worth $40, available for $28", and the gap between the two becomes a thing you feel you are receiving. That is why the saving so often gets spent twice — once on the item, and once in the mental arithmetic that treats $12 as money you now have spare.

At full price, no reference number is offered. You have to produce one yourself, from what the thing is worth to you. That is a slower, more effortful judgement, and it is the one that ends with you not buying things.

What research says

The clearest recent measurement of this comes from Park and Jang (2025), published in Frontiers in Psychology. They ran three experiments on US participants, varying only where the regular price sat relative to the discount price.

Study 1A (213 participants, headphones, about a 30% discount): fair-price estimates were 22.24**withnopromotionatall,**18.89 with the regular price on the left, and $17.35 with the discount price on the left. The difference between the two promotional layouts was statistically significant, F(1,207) = 4.22, p = 0.041, with a small effect size (d = 0.32).
Study 2 (121 participants, a travel bag): regular-price-left produced both a higher reference price (239.76**against**215.08, p = 0.022, d = 0.42) and a higher rating of the product's quality (5.90 against 5.56 on a 7-point scale, p = 0.048). The authors report that perceived quality fully mediated the price effect.
Study 1B (101 participants, a dietary supplement) found something more interesting. Without a quality-certification mark on the packaging, the layout effect was strong ($26.31 against 21.02,p=0.03).**Withacertificationmark,theeffectdisappeared**(27.19 against $28.27, p = 0.64).

That last result is the practical one. When people had an independent signal of what the product was actually worth, the price framing stopped mattering. The framing fills a vacuum. Give the vacuum something real and it has nothing to work with.

An everyday example

You are not shopping. You open an app to check one thing, and a banner says 30% off, two days left.

You look at a jacket. You do not ask "would I pay $63 for a jacket?" You ask "would I pay $63 for a $90 jacket?" — and that is a different question with a different answer, because the second one has an answer built into it. The $27 becomes something you are being given rather than something you are not spending. Then a second number appears, "only 2 left", and the decision gets faster rather than better.

You buy it. The next day it is fine. It is just that you were not looking for a jacket, and the jacket was not the thing that changed.

What this does not necessarily mean

It does not mean you are bad with money. This is a feature of how prices are read, not a flaw in your character. The effect was produced in a controlled study by moving two numbers a few centimetres apart.
It does not mean the item is a bad buy. Sometimes a thing you wanted anyway goes on sale. The pattern described here is about where the decision came from, not about whether the purchase was wrong.
It does not mean the effect is large. The effect sizes in this study were small to moderate (d = 0.32 to 0.68), the samples were between 101 and 213 people, and the authors list their own limits: only moderate discounts of around 30% were tested, vertical price layouts were not compared, brand perception was not accounted for, and the samples "may not represent all demographic groups well."
It does not mean the familiar claims about spending are all solid. The widely repeated idea that paying with cash hurts more than paying by card is, on current evidence, less settled than it sounds. One 2026 undergraduate honors capstone from UC Riverside found the opposite ordering in hypothetical $20 scenarios — but it is not peer-reviewed, and 577 of its 832 participants failed an embedded attention check. It is mentioned here only as a reason not to repeat the cash-versus-card claim with confidence, not as evidence for the reverse.
And it is not a verdict on anyone else. This is a pattern, not a diagnosis, and knowing about it is not a licence to judge how somebody else spends.

Practical things to try

Name your own number before you look at theirs. Decide what you would pay if the item simply cost that all year. Write it down. Then look at the price. This is the one step that actually addresses the mechanism, because it means you arrive with a reference price instead of borrowing one.
Stop calculating the saving. It is not money you had. Saying "I saved $27" out loud is what converts it into money you can spend.
Find the certification. Study 1B's finding generalises usefully: look for an independent signal of what the thing is worth — a review you trust, a specification you understand, the price history. Any real information shrinks the room the framing works in.
Put time between the price and the purchase. A day for small things, a week for anything you would have to explain to someone. Insight does not switch the effect off; distance does.
Treat urgency cues as information about the seller. A countdown or "only 2 left" tells you something about how the page was built, not about the product.
Decide what you are shopping for before you open the app, and buy only that. Most unplanned purchases are not decisions that went wrong. They are decisions that were never scheduled.

When professional help may be appropriate

Everything above describes an ordinary pattern in ordinary shopping. If spending feels genuinely out of your control, if it is causing you distress or financial harm, if you are hiding it, or if it has become the main way you manage difficult feelings, that is worth talking to a doctor or a qualified therapist about — and it is a different thing from what this article describes. Nothing here is a diagnosis or financial advice.

Which number is doing your deciding?

The six-question quiz below is about how you actually decide, not how you would like to. It sorts you into one of four patterns and gives you three things to do about that one.

Frequently Asked Questions

Q: Why do I buy things in a sale that I would never buy at full price?

A: Because the sale supplies the number you compare against. A price judgement is made against a reference price, and a discount hands you one ready-made: "worth $90, yours for $63" instead of "costs $63". Park and Jang's 2025 study measured this directly — the same headphones were judged worth $18.89 or $17.35 depending only on which price sat to the left. At full price you have to build your own reference figure, which is a slower judgement and the one that more often ends in not buying.

Q: What is the psychology of impulse buying in the simplest terms?

A: A fast comparison beats a slow valuation. You can compare two numbers in front of you almost instantly; working out what a thing is worth to you takes effort and attention you may not have at 10pm. Impulse buying is usually not a failure of willpower in the moment — it is the cheaper mental operation winning, because the more expensive one was never started.

Q: Does knowing about this stop it happening?

A: Mostly not, which is one of the more irritating things about this area. Reference-price effects operate on the judgement itself rather than on your reasoning about the judgement, so you can spot the framing and still feel the pull. What reliably helps is changing the situation rather than your insight: deciding your number first, and putting time between seeing a price and paying it.

Q: How do I stop impulse buying before Black Friday?

A: Write down, now, what you are actually shopping for and what you would pay for each item at any time of year. Doing it in advance is the point — it means that in late November you are checking a list rather than evaluating an offer. Mind Decoded's view is that the useful work happens weeks before the sale, because during the sale you are being handed reference prices faster than you can build your own.

Q: Is the "saving" real?

A: Sometimes. A discount off a price nobody was paying is not a saving, and a discount off a price you were genuinely about to pay is. The way to tell is the number you wrote down before you looked. Without that number, there is no way to distinguish the two cases, which is precisely why the framing works so well.

Q: Why does a quality mark change anything?

A: In Park and Jang's second study, adding a certification mark to the packaging made the price-layout effect disappear entirely. The reasonable reading is that framing has most power where real information is absent. When you have an independent way of judging what something is worth, the arrangement of the numbers stops being the best evidence available.

Q: Is this the same as shopping addiction?

A: No, and the distinction matters. This article is about an everyday pattern in how prices are read — something close to universal, measured in people who were simply shown two numbers. Compulsive spending that causes distress or harm is a clinical matter and belongs with a professional, not with an article about reference prices.

If you want to work on this

The free step. Mind Decoded's newsletter is where this kind of thing arrives — one everyday pattern at a time, with the research and its limits. Sign up at our-mind-decoded.com.

The paid one. If you want the "write the number down first" habit on paper, the No-Spend Challenge Tracker is a seven-page printable: a 30-day grid, a spending-trigger log, and a want list with a wait-until date next to each thing. Undated, A4 and US Letter, instant PDF. €5.00 →

Get the No-Spend Challenge Tracker — €5.00

Sources

Park, E. Y., & Jang, J. M. (2025). "Psychological effects of horizontal price display: how left-right location shapes reference price and perceived quality." Frontiers in Psychology, 16, Article 1497372 — https://doi.org/10.3389/fpsyg.2025.1497372 — all fair-price figures, the quality ratings, the certification-mark result, the statistics, and the authors' stated limitations.
Guidotti, M. S. (2026). "Do college students experience more pain of paying with cash or card?" UC Riverside Honors Capstones 2025–2026, eScholarship — https://escholarship.org/uc/item/5f13p45z — cited only in "What this does not necessarily mean", and explicitly as an undergraduate honors capstone rather than peer-reviewed research. 832 participants, hypothetical $20 scenarios; 577 of 832 failed an embedded attention check, which the author reports.

Not claimed anywhere on this page: any figure for how many people buy on impulse; any percentage of purchases that are unplanned; any claim about brain regions; any AI-search or Google-search volume; any claim that this article's advice has been tested. The Black Friday date (27 November 2026) is the fourth Thursday of November plus one day, which is arithmetic rather than a cited fact.