A study revealed that manipulating lip size could impact perceived facial attractiveness, with pronounced gender-specific preferences that may have implications for cosmetic procedures and body image.

In the study, published in the Proceedings of the Royal Society B, researchers from the University of Sydney and the University of Queensland found that female faces were rated more attractive with plumper lips, whereas male faces were perceived as more attractive with thinner lips. More surprisingly, these preferences were primarily driven by own-gender biases.

"Female [individuals] showed peak preference for expanded lips when viewing female faces; male [individuals] showed peak preference for contracted lips when viewing male faces," the study authors wrote. "Distortions of lip size therefore mostly influence own-gender attractiveness ratings," they added.

The researchers recruited 32 participants (16 male individuals and 16 female individuals) who rated the attractiveness of 24 face identities (12 male individuals and 12 female individuals) with lips manipulated across 7 different size levels.

Adaptation Effects on Attractiveness Perception

Following adaptation to faces with enlarged or contracted lips, participants’ perceptions of attractiveness shifted toward the adapted lip size. This renormalization effect occurred whether adaptation and testing happened within the same identity or between different identities, though the effect was stronger for within-identity conditions.

"Viewing faces with artificially altered lip size therefore powerfully influences attractiveness judgements," the study authors stated. "Outside the laboratory, cosmetic procedures to increase lip size are popular. Our findings indicate that lip plumping will mostly appeal to women rather than men (who prefer thinner lips), and exposure to expanded lips renormalizes attractiveness to a larger baseline and may lead to lip dysmorphia," they suggested.

Feature-Based Processing Challenges Holistic Face Perception

Notably, adaptation to isolated lips (without facial context) also produced significant shifts in attractiveness ratings of whole faces. This finding related to theories of face perception that focused on holistic processing.

"The theory of holistic processing for face perception posits that isolated lips would be represented separately from whole faces with lips," the study authors explained. "If this is the case, and holistic processing underwrites facial attractiveness, then adapting to isolated lips should have no impact on the subsequent judgements of whole faces," they detailed.

The results suggested that lip size might be encoded separately from the whole face or other local features, contradicting the conventional understanding that faces are processed primarily as integrated wholes rather than collections of individual features.

Implications for Cosmetic Procedures

The researchers argued that their findings had significant implications for cosmetic procedures, particularly lip augmentation. While such procedures remained popular among women, the study suggested these modifications might not enhance attractiveness in the eyes of male observers.

"Our data suggested that costly cosmetic procedures that increase female lip size, such as injectables and lip-enhancing surgeries, may not appeal to men," the study authors noted.

Additionally, the adaptation effects observed raised concerns about a potential maladaptive cycle in which continuous exposure to artificially enlarged lips could lead individuals to perceive only increasingly plumper lips as attractive.

"Exposure to distorted lips that have been artificially expanded beyond biological limits could initiate an iterative process whereby only further expansion to even plumper lips will be perceived as attractive to an adapted observer. Ultimately, such a process would culminate in lip dysmorphia," the study authors cautioned.

This study represented one of the first to specifically manipulate lip size alone to investigate the role of local features in facial attractiveness perception, providing valuable insights into both the psychological mechanisms of beauty perception and potential consequences of cosmetic interventions.

The authors declared having no competing interests.