Forget plastic surgery -- smiling can make you look a lot younger than you actually are.

That’s the finding of a recent study by researchers at the Institute for Human Development in Berlin published in the current issue of Psychology and Aging.

Researchers found that various facial expressions can affect how people estimate age and quite often smiling makes people look more attractive and therefore younger. The study also discovered that older faces were “more difficult to estimate than the age of younger faces.”

“Facial expressions had a substantial impact on accuracy and bias of age estimation,” the study noted. “Relative to other facial expressions, the age of neutral faces was estimated most accurately, while the age of faces displaying happy expressions was most likely underestimated.”

The study included 154 German men and women ranging in various ages from young to old who were each called on to examine more than 2,000 photographs of 171 people and then estimate their age.

The photos with neutral facial expressions produced the most accurate age estimates, and those of older women generally drew lower age estimates than those of older men.