When a Small Difference Tips the Sale: The Lopsided Logic of Product Comparisons

For most consumers setting out to buy something new, comparing attributes becomes a part-time job. Hours of searching across review and comparison sites, browsing nearly endless cross-product comparisons: less expensive and more storage, but shorter battery and fewer megapixels.

“It is well documented that a product’s appeal is influenced by how it compares to other products,” write Imperial Business School’s Guy Voichek and Yale SOM’s Nathan Novemsky. “However, not much is known about how the size of a difference between products affects the intensity of contrast effects.”

An article by the researchers published in the Journal of Consumer Research gets at the heart of this question, and the answer is surprising. Intuitively, you might expect that the bigger the gap between two products, the stronger the comparison effect in both directions: the better one looks better, the worse one looks worse, and both effects scale up. But Voichek and Novemsky find that the relationship only holds on one side of the ledger. When a product is the worse of the two being compared, the size of the gap matters. When it’s the better of the two, the size of the gap barely registers. Consumers see that one product is superior and largely stop there.

This pattern, which the authors call asymmetric scope sensitivity, rests on two well-established findings. First, when people compare options, they tend to identify which is better before considering by how much. Second, people spend fewer cognitive resources evaluating good things than bad things. Put those together, and consumers comparing two products will fully process the size of the gap when looking at the loser, but skip that step when looking at the winner.

Building the case across product categories

In a first set of studies, the researchers asked participants to evaluate products presented side-by-side in the kind of comparison table familiar from any e-commerce site. They varied two things: whether a target product was rated better or worse than its competitor, and whether the difference was small or large. The pattern was striking. For products rated worse than the competition, shrinking the difference made them seem meaningfully closer in quality. For products rated better, the size of the difference didn’t move the needle: being slightly better delivered the same boost as being much better. A follow-up study extended this to a setting where participants evaluated both products in a pair, the way shoppers actually do, and the asymmetry held even when the same gap was examined from both directions moments apart.

What it means for choice

The next set of studies translated these effects into purchase behavior. In one, participants chose between two mobile phones. When the phones were identical, sales split evenly (with some people choosing to continue shopping for another product). When researchers degraded one phone slightly by making it a touch cheaper but with marginally worse specs, sales of the slightly worse phone held steady, while sales of the slightly better phone nearly doubled. Overall purchase rates jumped from 57% to 80%.

Another study examined products that involve a tradeoff — better on one attribute, worse on another. Shrinking the tradeoff (making the differences on both attributes small) made products meaningfully more attractive, because the inferior attribute looked less bad while the superior attribute didn't lose any of its shine.

Why it happens — and how to undo it

A final pair of studies pinned down the mechanism. When evaluating the worse product in a pair, consumers spent more time on the comparison page and were more likely to report having considered the size of the gap. When evaluating the better product, they moved faster and gave the magnitude less thought.

Crucially, when researchers simply prompted participants to consider not just whether but by how much one product was better, the asymmetry disappeared. Positive contrast became as scope-sensitive as negative contrast. This confirms that the effect is about attention, not value.

What practitioners can take from this

The findings cut against a long-standing assumption in marketing that any comparison hurts the loser more than it helps the winner. For minor quality differences, Voichek and Novemsky show the opposite. “Providing a comparison between products with minor quality differences significantly enhances the appeal of one product without diminishing the attractiveness of the other,” they write.

That has three practical implications. First, marketers can lift sales of one product without cannibalizing another by inviting comparisons between similar items. When highlighting a select few attributes, choose those where the gap is small to capture disproportionate upside without the corresponding downside. Second, manufacturers may not need groundbreaking improvements to gain ground on close competitors; small advantages can generate as much positive contrast as large ones. A modestly improved next-gen model can punch well above its weight.

Third, and counterintuitively, when an offering really is far superior to the competition, simply showing the numbers isn’t enough. Voichek and Novemsky point to Samsung’s classic “It doesn't take a genius” ad, which compared a Galaxy phone’s 790 hours of standby time to the iPhone’s 225. The authors suggest “the ad might have been more effective if it were to highlight, for example, that the Galaxy has much longer battery life rather than simply presenting the two attribute values and assuming consumers will consider the size of the difference.”

For consumers, the lesson is the mirror image. “Reminding consumers to consider not only whether, but also by how much, products are better and worse than one another,” the authors note, “would help them avoid giving too much weight to minor differences or too little weight to major differences.”

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