Want to look younger? Well, you should probably stop smiling.

According to a new study from Ontario's Western University and Israel’s Ben-Gurion University, smiling can actually make you look a year older than if you’re wearing a straight, neutral face. Does that surprise you? If so, your look of profound shock can actually drop time off your perceived age.

“We associate smiling with positive values and youth,” the study’s co-author, Melvyn Goodale, director of Western University’s Brain and Mind Institute, said in a press release. “Think of all the skin-care and toothpaste companies that sell the same idea every day.”

Although “well-rooted in popular media,” that idea, the study says, “is a complete misconception.”

In “The effects of smiling on perceived age defy belief,” which was published on May 8 in the Psychonomic Bulletin and Review, researchers showed university students images of people with smiling, neutral and surprised expressions. The study’s participants routinely believed that the smiling faces were the oldest and the surprised faces were the youngest.

Goodale said that a smile can age you because it forces people to see wrinkles forming around your eyes. A surprised face, by contrast, smooths out such lines.

“The striking thing was that when we asked participants afterwards about their perceptions, they erroneously recalled that they had identified smiling faces as the youngest ones,” Goodale added. “It may seem counter-intuitive, but the study shows that people can sincerely believe one thing and then behave in a completely different way.”