As the results suggest, fantasy plays a role in many Americans' sex lives. Among sexually active adults, 51 percent (men and women alike) say they talk with their partner about their fantasies in order to enhance their sex lives. And as noted, men are more likely to fantasize about threesomes, an unexpected sexual encounter with someone new, or cheating on their spouses.
Looking at pornographic Web sites likewise attracts more men. Fewer men or women fantasize about sex outdoors (likely because so many have done it), or sex at work.
The role of fantasy in a happy sex life is not clear-cut. Discussing fantasies does lend itself to excitement: Forty-four percent of couples who talk about their fantasies call their sex lives very exciting, compared with 28 percent of those who don't. People who discuss their fantasies with their partner are also 10 points more apt to enjoy sex a great deal. But they're just six points more apt to be very satisfied with their sex life, and no more likely to be satisfied with their marriage or committed relationship.
A regression analysis (measuring the effect of one factor by controlling for the influence of others) finds that factors related to Americans' satisfaction with their sex lives include how exciting they rate their sex lives, their frequency of sex (especially for married men), how regularly they experience orgasms, whether they're married or in a committed relationship and, only for people in a relationship, their lifetime number of sex partners (more partners is related to less satisfaction).
Positive contributors to an "exciting" sex life include wearing something sexy, discussing fantasies, age (excitement diminishes with age), being married or in a committed relationship, and frequency of orgasms.
On the negative side, sexual excitement declines with the duration of a marriage or committed relationship -- losing the spark. Nonetheless, people who are married or in a committed relationship still are more likely to be satisfied with their sex lives than those who are not in such a relationship, controlling for other factors such as age and frequency of sex.
Items missing from the list of contributors to a satisfying (rather than exciting) sex life also are notable; age, for example, is not a significant predictor. (That's limited of course to people who are active sexually, which excludes most senior citizens.)
Another regression analysis finds that Americans' satisfaction with their sex lives is a significant predictor of their satisfaction with their marriages or committed relationships. Satisfaction with family lives, and to a lesser degree with finances and social lives, also predict satisfaction with marriage, while satisfaction with health and work do not.
While directionality is hard to establish, it seems more plausible that satisfaction with sex fuels satisfaction with marriage than the reverse. That's because more people are very satisfied with their marriages than are very satisfied with their sex lives. If satisfaction with marriage drove satisfaction with sex, this gap would not exist.