Distortions of lip size bias perceived facial attractiveness

Perceiving faces as attractive or not guides decisions to approach or date a person and can sway opinions in recruiting and legal proceedings. However, the mechanisms underlying facial attractiveness are not fully understood. While popular models of face recognition emphasize holistic processing, individuals often attempt to enhance their own attractiveness in feature-centric ways (cosmetic surgery, make-up, injectables). Here, we use a local feature manipulation (lip expansion/contraction) and show that it alters the perceived attractiveness of male and female faces. Females showed peak preference for expanded lips when viewing female faces; males showed peak preference for contracted lips when viewing male faces. Distortions of lip size therefore mostly influence own-gender attractiveness ratings. Next, we tested whether visual adaptation to expanded or contracted lips would bias subsequent attractiveness judgements, and found peak attractiveness shifted towards the adapted lip size (e.g. expanded lips were preferred following exposure to expanded lips). Viewing faces with artificially altered lip size therefore powerfully influences attractiveness judgements. Outside the laboratory, cosmetic procedures to increase lip size are popular. Our findings indicate that (i) lip plumping will mostly appeal to women rather than men (who prefer thinner lips), and (ii) exposure to expanded lips renormalizes attractiveness to a larger baseline and may lead to lip dysmorphia.