How to use advertising appeals to promote green purchase behaviour —The double-edged sword effect of a large usage-based scale frame

Why the Way We Count Can Change How We Go Green

Imagine two ads for the same water‑saving washing machine. One says it saves 5 liters of water every time you wash. The other boasts 5000 liters saved over its lifetime. The numbers describe the same benefit, but they feel very different. This paper explores how such number tricks in green advertising can nudge people toward—or away from—buying eco‑friendly products, and why this "bigger is better" style of messaging can help and hurt at the same time.

Big Numbers, Same Reality

The researchers focus on a simple idea: companies can describe an environmental benefit using either small everyday units or large lifetime totals. In their study, they used a water‑efficient washing machine. Some people saw an ad saying it saves 5 liters of water per wash (a small‑number frame). Others saw an ad saying it saves 5000 liters over 1000 washes (a large‑number frame). Both statements are mathematically identical, but the second one feels more impressive because the number is larger. The team wanted to know whether this difference changes how valuable people think the product is and how likely they are to buy it.

How Our Minds Shortcut the Math

Many of us do not stop to check the math in everyday ads. Instead, we rely on mental shortcuts. One such shortcut is the "numerosity" rule of thumb: bigger numbers seem to signal more of something, regardless of the units used. The study shows that this shortcut works in favor of green products. When the benefit was described with a large number, people reported higher overall value for the washing machine—both in terms of helping the environment and saving money over time. In turn, this stronger sense of value made them more willing to consider buying the product.

When Big Numbers Backfire

However, there is a catch. The same big numbers that make a product look generous can also set off alarms. Some consumers look more carefully at unusual or flashy messages and wonder if they are being manipulated. In the study, people who saw the large‑number version of the ad were also more skeptical: they were more likely to doubt the truthfulness of the claim and to suspect marketing tricks. This suspicion reduced their willingness to buy. In other words, the large‑number message cut both ways—raising perceived value but also raising doubt, partially canceling out its own positive impact.

Different Minds, Different Reactions

The authors also found that not all consumers react to these messages in the same way. People who naturally focus on hopes, gains, and improvement—called promotion‑focused consumers—responded well to the large‑number frame. For them, the big lifetime savings strengthened the feeling that the product was worthwhile, increasing their intention to buy. By contrast, people who think more about duties, safety, and avoiding loss—prevention‑focused consumers—were more wary. For them, the large‑number frame boosted skepticism, making them less inclined to purchase. The same ad that excites one group can unsettle another.

What This Means for Green Choices

To a layperson, the message of this study is straightforward: the way numbers are framed in green ads can meaningfully change how eco‑friendly products are seen. Large totals can make benefits feel bigger and more attractive, but they can also raise eyebrows and breed distrust, especially among cautious shoppers. For policymakers and companies, this means that "louder" green claims are not always better; they need to be paired with credible proof and tuned to the mindset of the audience. For consumers, it is a reminder to look past the size of the number and pay attention to what it really represents in everyday use.

Citation: Hou, C., Li, T., Gu, Y. et al. How to use advertising appeals to promote green purchase behaviour —The double-edged sword effect of a large usage-based scale frame. Humanit Soc Sci Commun 13, 268 (2026). https://doi.org/10.1057/s41599-026-06633-1

Keywords: green advertising, number framing, consumer behavior, sustainability marketing, purchase intention