For a believable impression neither the corners of the mouth should be raised too high nor the teeth too strong
The subjects evaluated the smile of different computer-animated faces.
Minneapolis (USA) - Less is often more - this also obviously applies to the perfect smile. If the corners of the mouth are raised too much, the impression of an honest smile does not often arise. Likewise, it is not always advantageous to show too much teeth, according to US psychologists in the "PloS ONE". A positive effect, however, is when the smile spreads symmetrically on the face. The researchers had investigated the effect of different smiling expressions using computer-generated faces and thus determined what makes a pleasant and pleasant smile.
"We define a 'successful smile' as one that is classed as effective, sincere and sympathetic - in the perceptual sense of these words," write Nathaniel E. Helwig of the University of Minnesota and colleagues. The psychologists used 3D computer models in which they could vary different parameters of a smile in a precisely defined way - including alignment of the angle of the mouth, the extent of the smile and how much the teeth are visible. The differently animated faces presented more than 800 subjects. They should assess how effective, sincere, sympathetic and emotional they felt the smile.
"We have found that a successful smile can be expressed through a number of different spatio-temporal processes," the psychologists write. Such a smile involves a complicated balance of the angle of the mouth, strength of the smile, and showing the teeth. The Floskel "Much helps a lot" is not tendenziell. For a more extended smile or one that makes more teeth visible, the subjects often judged as less pleasant than a more reserved one. However, this statement can not be generalized, since the overall impression depends on the interaction of the individual components in the individual case. In addition, symmetry plays a role: a smile that unfolds almost simultaneously at the right and left is felt more appealing.
The results are not only of a theoretical nature, but can be used in the eyes of researchers in a number of areas, such as surgery to restore faces after an accident, rehabilitation after a stroke or even for computer graphics. In future studies, the psychologists want to investigate further combinations of the parameters used, in order to get a more accurate picture of their interaction. In addition, they can imagine extending the method to other facial expressions, such as surprise, anger, fear, or grief.