The Influence of Width Ratios on Structural Beauty in Male Faces

Abstract

This study investigates the relationship between interocular distance relative to overall facial width (width ratio) and perceived subjective beauty in male faces. Building on the methodology of Pallett et al. (2010), who found that average proportions in female faces were rated as most attractive, the current study aimed to test this hypothesis in male faces. Faces from the Chicago Face Database (Ma et al., 2015) were morphed into average faces within three groups (with low, medium, and high width ratios), each composed of 96 or 97 individual images. These three average faces were then systematically manipulated in their width ratios across three levels in both directions, respectively, resulting in a total of 21 comparable faces. The use of multiple base faces served as a control for potential artifacts of image processing. Consequently, comparisons were restricted to within-group pairs to avoid confounding by co-varying facial features (e.g., skin tone), which precluded direct cross-condition comparisons but ensured internal validity. In a two-alternative forced-choice task, participants selected the more beautiful face from each pair. The data were analyzed using a Bayesian model which enables inference of the width ratio perceived as most beautiful. Results support the hypothesis that averageness in facial proportions correlates with higher perceived attractiveness. The study highlights the importance of controlling for image manipulation, including attempts at methodological implementation, and of considering ethnicity as a potential moderating variable. These findings offer a data-driven foundation for understanding facial aesthetics and cognitive processes of human perception, with applications in advertising, artificial face generation, and plastic surgery.

Figures (8)

• Figure 1: Left: Scatterplot of faces from the Chicago Face Database, with attractiveness ratings on the y-axis and width ratios on the x-axis. Colors indicate group membership: low (orange), medium (green), and high (blue) width ratios, defined by dividing the dataset into thirds based on width ratio values. Vertical lines represent the mean width ratio of each group. Note: The attractiveness ratings provided by the database were not used in this study’s assessment of beauty. Right: Example image from the Chicago Face Database (marked with a star in the plot).
• Figure 2: Left: Facial template showing the measurement points used to calculate the width ratio, defined as the ratio of inner eye distance to total face width. The width ratio of the depicted face is indicated above the image. Note that this is an example image not used for our study as it is a female face. Right: Morphing mask used to generate the average faces, shown here overlaid on the composite face of the low width-ratio group.
• Figure 3: Average composite faces created from one-third of the male faces in the Chicago Face Database grouped by ratio: low (left), medium (middle), and high (right).
• Figure 4: Overview of all stimuli used in the experiment, consisting of 21 manipulated faces generated by morphing 97, 96, and 97 images from the low (a), medium (b), and high (c) width ratio groups, respectively. From left to right in each condition: $-100$, $-66$, $-33$, $0$, $+33$, $+66$, $+100$ (arbitrary units). The original average face ($0$) served as the baseline and was manipulated to generate the other faces. (d) The diagram below shows the program-calculated width ratios of all faces, verifying the consistency and validity of the manipulations.
• Figure 5: Illustration of the methodological procedure: (1) plot of faces from the Chicago Face Database by width ratio, (2) generation of three averaged faces (low, medium, high width ratios), (3) manipulation of each average face's width ratio using the Liquefy function in Adobe Photoshop, (4) pairwise comparisons of all manipulated faces within each condition, including two comparisons for each possible pair and one self-comparison per average face, (5) expected shift in perceived beauty towards the average face.