Smile dimensions affect self-perceived smile attractiveness

Abstract

Facial expressions play a leading role in human interactions because they provide signaling information of emotion and create social perceptions of an individuals' physical and personality traits. Smiling increases socially perceived attractiveness and is considered a signal of trustworthiness and intelligence. Despite the ample information regarding the social importance of an attractive smile, little is known about the association between smile characteristics and self-assessed smile attractiveness. Here we investigate the effect of smile dimensions on ratings of self-perceived smile attractiveness, in a group of 613 young adults using 3D facial imaging. We show a significant effect of proportional smile width (ratio of smile width to facial width) on self-perceived smile attractiveness. In fact, for every 10% increase in proportional smile width, self-perceived attractiveness ratings increased by 10.26%. In the present sample, this association was primarily evident in females. Our results indicate that objective characteristics of the smile influence self-perception of smile attractiveness. The increased strength of the effect in females provides support to the notion that females are overall more aware of their smile and the impact it has on their public image.

Figure 1

Selected landmarks on 3D images: (a) Right and left most lateral facial point (at the intersection where the outer outline of the ear connects to the face); (b) Right and left corner of the mouth; (c) Upper stomion (the midpoint of the upper lip inferior border); (d) Lower stomion (the midpoint of the lower lip superior border); (e) Upper vermillion midpoint (the midpoint of the upper lip superior border); (f) Lower vermillion midpoint (the midpoint of the lower lip inferior border); (g) Menton (the most inferior point of the median plane of the chin); (h) Right and left most median point of the upper eyebrow ridge. (Image was created using Viewbox 4 software (version 4.1.0.1 BETA, http://www.dhal.com/viewboxindex.htm). The projection of the midpoint between the right and left most median points of the upper eyebrow ridge on the surface image was considered the most superior midline point of the face (point MP) and was used to define facial height. (Image was created using Viewbox 4 software (version 4.1.0.1 BETA, http://www.dhal.com/viewboxindex.htm).

Figure 2

Bland–Altman plot showing the level of agreement in self-perceived facial attractiveness between the first and second visits of 93 subjects. (Graph was created using SPSS version 26.0, https://www.ibm.com/products/spss-statistics).

Figure 3

Linear regression of proportional smile width on self-perceived smile attractiveness, in (a) females and (b) males. (Images were created using SPSS version 26.0, https://www.ibm.com/products/spss-statistics).