The "Central Tendency Bias" in the assessment of facial attractiveness in group-based and individual ratings-A survey-based study in 727 volunteers

Abstract

Background: The increasing number of esthetic procedures emphasizes the need for effective evaluation methods of outcomes. Current practices include the individual practitioners' judgment in conjunction with standardized scales, often relying on the comparison of before and after photographs. This study investigates whether comparative evaluations influence the perception of beauty and aims to enhance the accuracy of esthetic assessments in clinical and research settings.

Objective: To compare the evaluation of attractiveness and gender characteristics of faces in group-based versus individual ratings.

Methods: A sample of 727 volunteers (average age of 29.5 years) assessed 40 facial photographs (20 male, 20 female) for attractiveness, masculinity, and femininity using a 5-point Likert scale. Each face was digitally edited to display varying ratios in four lip-related proportions: vertical lip position, lip width, upper lip esthetics, and lower lip esthetics. Participants rated these images both in an image series (group-based) and individually.

Results: Differences in the perception of the most attractive/masculine/feminine ratios for each lip proportion were found in both the group-based and individual ratings. Group ratings exhibited a significant central tendency bias, with a preference for more average outcomes compared with individual ratings, with an average difference of 0.50 versus 1.00. (p = 0.033) CONCLUSION: A central tendency bias was noted in evaluations of attractiveness, masculinity, and femininity in group-based image presentation, indicating a bias toward more "average" features. Conversely, individual assessments displayed a preference for more pronounced, "non-average" appearances, thereby possibly pointing toward a malleable "intrinsic esthetic blueprint" shaped by comparative context.

Keywords: Esthetic rating; Eye tracking analyses; Facial beauty; Facial perception; Lip esthetics.