New research from the University of Minnesota challenges the notion that a dazzling, wide smile is the key to making a good impression. Instead, a 'perfect smile' appears to be one that strikes a balance between being broad enough and showing just the right amount of teeth.
The study's findings, published in Plos One, come from an investigation into the intricate mechanics of facial expression. Dr Stephen Guy, a co-author of the research, highlighted the importance of smiles in daily communication, often overlooked until it's too late. The team believes their work could offer significant value to clinicians working to restore facial movement and expression in patients with facial paralysis.
To pinpoint the characteristics of an ideal smile, researchers presented 802 members of the public with 3D computer-animated virtual faces displaying various smiles. These faces differed in mouth angle, breadth, and number of teeth shown, as well as having one specific smile manipulated for symmetry. Each animation was shown for 250 milliseconds, and participants were asked to rate the smiles on scales such as 'fake' to 'genuine' and 'creepy' to 'pleasant', alongside emotional intent and overall effectiveness.
The analysis revealed that the most positively rated smiles had mouth angles between 13 and 17 degrees, a width between 55% and 62% of the distance between the pupils of the eyes. While acknowledging there isn't just one perfect smile, Dr Guy stressed that variations don't inherently make a smile 'bad'. In fact, unsuccessful smiles often featured high angles, significant breadth, and a large display of teeth.
Interestingly, the study also found that a slight asymmetry could lead to higher ratings than a perfectly symmetrical smile, provided the delay between the two sides did not exceed 125 milliseconds. The researchers acknowledge limitations, noting their model primarily focused on the mouth's impact, despite previous research indicating the crucial role of the eyes. This research builds upon existing understanding of facial perception, offering a detailed breakdown of specific smile parameters. Future work is expected to integrate broader contextual factors, including the eyes and overall body language.