Via NCBI ROFL:
Introduction. Recent studies have uncovered multiple markers of vaginal orgasm history (unblocked pelvic movement during walking, less use of immature psychological defense mechanisms, greater urethrovaginal space). Other markers (perhaps of prenatal origin) even without obvious mechanistic roles in vaginal orgasm might exist, and a clinical observation led to the novel hypothesis that a prominent tubercle of the upper lip is such a marker. Aims. To examine the hypothesis that a prominent tubercle of the upper lip is associated specifically with greater likelihood of experiencing vaginal orgasm (orgasm elicited by penile-vaginal intercourse [PVI] without concurrent masturbation). Methods. Women (N = 258, predominantly Scottish) completed an online survey reporting their frequencies of various sexual activities and corresponding orgasms, age, and the prominence of the tubercle of their upper lip. Social desirability response bias was also assessed. Main Outcome Measures. Multivariate associations of lip tubercle prominence with vaginal orgasm (ever and past month consistency) and with orgasm by other means. Results. A prominent and sharply raised lip tubercle was associated with greater odds (odds ratio = 12.3) of ever having a vaginal orgasm, and also with greater past month vaginal orgasm consistency (an effect driven by the women who never had a vaginal orgasm), than less prominent lip tubercle categories. Lip tubercle was not associated with social desirability responding, or with orgasm triggered by masturbation during PVI, solitary or partner clitoral or vaginal masturbation, vibrator, or cunnilingus. Conclusions. The results are discussed in light of the unique nature of vaginal orgasm and the possibility of prenatal developmental influences. Brody S and Costa RM. Vaginal orgasm is more prevalent among women with a prominent tubercle of the upper lip.
Source: “Vaginal Orgasm Is More Prevalent Among Women with a Prominent Tubercle of the Upper Lip.” from J Sex Med. 2011 Jun 15
By the way, the tubercle is the center area of the upper lip.
For more on sex and attraction: A Billion Wicked Thoughts: What the World’s Largest Experiment Reveals about Human Desire. I enjoyed it.