use their fantasies to "turn off" undesirable aspects of an act. Conversely, a person may use fantasy to focus and maintain arousal, such as a man receiving fellatio ignoring a distraction. Men tend to be aware of only parts of themselves during sex-—they are more likely to focus on the physical stimulation of one area, and as such, do not see themselves as a "whole". Many couples share their fantasies to feel closer and gain more intimacy and trust, or simply to become more aroused or effect a more powerful physical response. Some couples share fantasies as a form of outercourse; this has been offered as an explanation for the rise of BDSM during the 1980s — in order to avoid contracting HIV, people turned to BDSM as a safe outlet for sexual fantasy. Couples may also act out their fantasies through sexual roleplay. Fantasies may also be used as a part of sex therapy. They can enhance insufficiently exciting sexual acts to promote higher levels of sexual arousal and release. A 1986 study that looked at married women indicated that sexual fantasies helped them achieve arousal and orgasm. As a part of therapy, anorgasmic women are commonly encouraged to use fantasy and masturbation. Common fantasies The incidence of sexual fantasies is nearly universal, but vary by gender, age, sexual orientation, and society. However, because of a reliance on retrospective recall, as well as response bias and taboo, there is an inherent difficulty in measuring the frequency of types of fantasies. In general, the most common fantasies for men and women are: reliving an exciting sexual experience, imagining sex with a current partner, and imagining sex with a different partner. There is no consistent difference in the popularity of these three categories of fantasies. The next most common fantasies involve oral sex, sex in a romantic location, sexual power or irresistibility, and rape. According to a 2004 United States survey, the incidence of certain fantasies is higher than the actual performance. Gender differences Origins of sexual fantasies The sexes have been found to contrast with respect to where their fantasies originate from. Men tend to fantasize about past sexual experiences, whereas women are more likely to conjure an imaginary lover or sexual encounter that they have not experienced previously. Male fantasies tend to focus more on visual imagery and explicit anatomic detail, with men being more interested in visual sexual