Less is probably more when it comes to a convincing smile, a new study finds.
More than 800 people were shown a series of 3D computer-animated smiles and asked to rate them. The smiles differed in features such as amount, mouth angle, symmetry and how many teeth were shown.
Bigger smiles that showed more teeth tended to be rated as less effective, genuine or pleasant. Successful smiles were those with a pleasing balance of teeth, mouth angle and amount of smile, the investigators found.
The study team — led by Nathaniel Helwig from the University of Minnesota — also found that smiles were rated as more successful if they developed symmetrically on the left and right side of the face.
The findings could help guide facial reanimation surgery and rehabilitation for people with stroke and other medical conditions that affect facial expressions, the researchers said.
Findings from the study were published online June 28 in the journal PLoS One.
The U.S. National Library of Medicine has more on facial paralysis.