Don't Worry! Be Happy! Look Younger!

Forget the face lift. Skip the Botox. And ditch the pricey wrinkle creams. The secret to a younger-looking face may be looking happy, new research suggests.

Study volunteers were most likely to underestimate the age of happy faces.

"Our study is the first to show that facial expression affects both accuracy and bias in age estimation," says lead author Manuel Voelkle, a research scientist at the Max Planck Institute for Human Development in Berlin. It appears in the journal Psychology and Aging.

Pictures of happy faces can be misleading because smiling or laughing can flex muscles around the eyes and mouth, creating temporary wrinkles. Since it's hard to tell temporary wrinkles from real ones in photos, people give a less accurate age estimate, Voelkle says.

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He also suspects that smiling faces carry a halo effect, meaning we generally perceive a grinning person to be more positive, more attractive, and younger.

To explore how well people estimated age across the adult life span, researchers recruited 154 German men and women, who were young, middle-aged and older. In at least 10 different testing sessions, each participant was shown more than 1,000 faces and asked to guess the person's age in the photographs. The faces had angry, fearful, disgusted, happy, sad and neutral expressions.

The age of faces with neutral expressions were estimated most accurately — which helps justify those "natural expression, both eyes open" U.S. passport photos. But faces with more emotion tended to throw off age predictions.

The study found that as people got older, they're less accurate at correctly guessing someone's age. Younger people tended to underestimate a person's age while older people seemed to overestimate them.

It's helpful to sense how old someone is from a picture. Whether you're looking at a Facebook photo, LinkedIn profile, or surveillance camera video, correctly perceiving a person's age can make a difference to how we approach and interact with that individual.

"Age is one of the most important attributes we use to describe a person," Voelkle says.

Researchers were surprised to find that older female faces were estimated to be more than three years younger than older male faces. (Make-up wasn't the reason because all the photos were taken without the person wearing cosmetics, eyeglasses or jewelry.)

Voelkle suggests that ladies may pay more attention to their physical appearance than guys do. Or it could be that women have a longer life expectancy than men. Looking at it from this perspective, he says, "it's possible to conceive of age as distance to death, rather than distance from birth."