Orgasms can happen ... anywhere
Now to more pleasurable thoughts. Women may not need a guy, a vibrator, or any other direct sexual stimulation to have an orgasm, as exercise may do the trick. A study involving women who had experienced exercise-induced orgasms and a group who reported exercise-caused sexual pleasure found that 40 percent of these women had these experiences on more than 11 occasions in their lives.
Even so, most of the women in the "orgasm" group said they felt some level of embarrassment when exercising in public places, the researchers say in a 2012 issue of the journal Sexual and Relationship Therapy.
The elusive orgasm
While some women can orgasm with a little physical activity, about one in four women find reaching orgasm an elusive goal. Research detailed in August 2010 in the Journal of the British Association of Urological Surgeons found that for women ages 18 to 30 the No. 1 sex complaint is trouble reaching orgasm, while older women mostly complain about lack of sexual desire.
Science not helping
Unfortunately, science has not yet come to the rescue. A review of 101 studies on female orgasm disorder, in which a woman has trouble climaxing or reaching orgasm at all, showed treatments for the disorder are inadequate. In addition, the Food and Drug Administration reported in 2010 the drug flibanserin (female Viagra) didn't increase a woman's sexual desire.
Think good thoughts
But perhaps women can take things into their own hands, or minds, as other research has found a lack of erotic thoughts, and even negative thoughts, during sex are linked to the trouble some women have reaching orgasm. These negative or distracting thoughts fell into six categories: thoughts of sexual abuse, sexual failure, a partner's lack of affection, sexual passivity and control, things that had no erotic nature, and body shortcomings.
"There is no easy way to avoid negative or distractive thoughts," study researcher Marta Xavier Cuntim, a clinical psychologist in Portugal, told LiveScience at the time the study was published in 2011 in the journal Sexologies. "However, if we know that they exist, it is easier to learn to deal with them."
Taking sex outside the species is generally frowned upon. But back when humans had other hominin cousins to hang out with, things got cozy. Up until about 47,000 years ago, modern humans and Neanderthals likely interbed. However, research suggests that these liasons only occasionally resulted in offspring.
Wait a minute. What is sex, anyway? According to the famous Kinsey Reports, opinions vary. In a 2010 study by the Kinsey Institute, 45 percent said manual stimulation of the genitals is sex, 71 percent said oral sex is sex and 80 percent said anal intercourse is sex.
Equal rights in bed
Equality pays off between the sheets: Research published in October 2012 in the journal Sex Roles found that young men who believe that men should take charge in the bedroom were actually less likely to feel confident in sexual situations compared with guys who were less concerned with gender roles. The belief that men need to dominate may prevent them from communicating about sex with their partners or asking questions about things they don't know.
Gals enjoy larger penises
Does size matter? For some. A study published Sept. 24, 2012 in the Journal of Sexual Medicine found that women who report having frequent orgasms with vaginal stimulation are more likely to say they prefer sex with men with larger penises.
For what it's worth, the same study considered an "average" penis to be about the length of a U.K. 20-pound note or a U.S. dollar bill, which are 5.9 inches (14.9 centimeters) and 6.1 inches (15.5 cm) long, respectively. Across multiple studies, average erect or flaccid-but-stretched penis length ranged from 4.7 inches (12 cm) to 6.5 inches (16.7 cm).
Don't worry, guys
On the whole, however, women worry less about penis size than men, according to a 2007 review of research published in the British Journal of Urology International. Personality and grooming rank way higher on the list of concerns, the researchers found. Eighty-five percent of women were happy with their partner's penis size, compared with only 55 percent of men who were satisfied with their own penis.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.