323 women were interviewed and asked if they were more likely to orgasm vaginally with a longer-than-average or shorter-than-average penis. The longer penises won the day in this study. The women who reported the largest number of vaginal orgasms were more likely to report that longer is better.
“This might be due … to greater ability of a longer penis to stimulate the entire length of the vagina and cervix,” said researched Stuart Brody, a psychologist at the University of West of Scotland. He also said that “Male anxiety about penis size may not reflect internalized, culturally arbitrary masculine stereotypes but an accurate appreciation that size matters to man women.”
Nailing down the variables is tough, however. The women might have misreported — or the correlation of size and orgasms might have alternative explanations. Women who have more orgasms may prefer longer penises, but climax to shorter ones as well. Secondly, it might not be the size of the penis, but the confidence of the man that thrilled the women: well-endowed men may be more confident.
The research was made available in September on the Journal of Sexual Medicine.