Greet clients with a smile. It’s a basic rule for every team member. The bigger the better, right? Not so much.

Research using computer-animated 3-D faces suggests that less is more for a successful smile, according to a new study.

According to a study published in the open-access journal PLOS ONE, Nathaniel Helwig of the University of Minnesota and colleagues presented a series of 3D computer-animated facial models to 802 participants. Each model's expression was altered by varying the mouth angle, extent of smile and the degree to which teeth were on show, as well as how symmetrically the smile developed. Participants were asked to rate smiles based on effectiveness, genuineness, pleasantness, and perceived emotional intent.

The researchers found that a successful smile—one that is rated effective, genuine and pleasant—may contradict the "more is always better" principle, as a bigger smile which shows more teeth may in fact be perceived less well.

Successful smiles have an optimal balance of teeth, mouth angle and smile extent to hit a smile “sweet spot.” Smiles also were rated as more successful if they developed quite symmetrically, with the left and right sides of the faces being synced to within 125 milliseconds.

Source: 10.1371/journal.pone.0179708

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