When shoppers come across advertisements online, the shape of a button that reads “Shop now” or “Add to cart” can make a difference.

Online consumers are “significantly” more likely to click on an ad with a curvy design than those with sharp features, according to a University of South Florida study published this month.

While physical stores can use scents and touch to help create an experience that converts to sales, online shopping is heavily reliant on visual cues, according to the study.

There have been plenty of studies exploring how color, wording and interactivity can influence online shopping behavior. But there hasn’t been as much research on the effects that shapes can have on digital ads.

When it comes to shapes, the USF study published in the Journal of Consumer Research found rounded rectangle buttons have higher click rates than those with sharp 90-degree angles.

That subconscious preference can translate to more sales for businesses.

A human trait developed by evolution

It’s an “evolutionary” instinct, said USF Muma College of Business marketing researcher Dipayan Biswas.

Curvy elements evoke more positive feelings — such as friendliness, nurturing, femininity — while sharp angles have negative connotations associated with danger, Biswas said.

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“Human beings and animals are a little bit apprehensive about anything that has sharp-angled edges because they tend to hurt us,” he said. “That’s why children’s products almost never have sharp edges. They’re always rounded.”

Previous research on the shape of call-to-action buttons, such as those that say “Add to cart” or “Buy now,” have argued that because sharp features are perceived as more threatening, it makes them more effective at grabbing attention. It’s a similar logic to how the color red — commonly signaling a warning — is used in marketing.

But the USF study proposes the opposite is true: Softer features are more visually appealing.

The Tampa researchers set up an experiment where 50% of online traffic for an unnamed hotel chain was directed toward a website with curvy design and the other half with sharp rectangles. More people clicked on buttons for the curvy webpage, according to the study.

That led to an 15% increase in revenue and the hotel switching over to curvy buttons after the experiment, Biswas said.

USF conducted several different experiments tracking eye movements and click rates using businesses and marketing students as test subjects. In each one, curvier buttons had higher success.

How button shapes influence shopping

Framing does matter, Biswas said. The study suggests softer buttons should be primarily used for positive messaging like shopping.

“Sharp buttons work best if you’re trying to encourage people to avoid something,” Biswas said.

For an online shoe ad, a button reading “avoid discomfort” would be more effective with sharp edges. It could also be better used for “don’t drink and drive” or “stop smoking” campaigns, he said.

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More retailers have converted from sharp to curved online buttons in recent years. The Walmart grocery division switched to curved buttons in 2020. USA Today also tested curvy and sharp buttons.

Biswas said he was inspired to research this topic after hearing from Tampa Bay business leaders that many didn’t consider shapes into their online strategy and would “just randomly pick one.” The USF study shows that being more intentional about website design can generate more sales.

But it’s also a warning that these tactics may be increasingly used to manipulate shoppers to spend money.

“If you’re being influenced by these unconscious variables and you end up spending way more than you planned for,” Biswas said. “That’s usually not good for most people.”