Ah, sexual fantasy. It has one big advantage over sexual reality: You have total control over everything that happens. You won't be humiliated or suffer at the hands of a brutish lover unless, of course, that's what you want.

Consider the possibilities. Your fantasy partner can be a celebrity, the guy who works down the hall, or your best friend's mate. You enjoy complete choice of venue: a tropical island, an elevator, a tree swing. And the activity in question can range from romantic, longing glances to sexual gymnastics that would strain a circus contortionist.

So perhaps the most surprising fact about our fantasies is this: The sexual scenario we most often imagine is the ordinary, non-kinky intercourse with a past or current lover. Despite the potential for limitless freedom, our fantasies generally stay firmly tethered to reality.

Don't worry if you assumed most fantasies were a bit more risque. Even in today's tell-all culture, sexual fantasies remain one of our last taboos, something that people simply don't discuss.

"We tell each other almost everything--our sexual habits, who we lust for, how much money we make," notes Columbia University psychiatrist Ethel Person, M.D., author of By Force of Fantasy. "But I do not know the sexual fantasies of my closest friends. We regard fantansies as too revealing. They're treasured possessions, yet we're ashamed of them."

Even psychologists long found sexual fantasy vaguely disreputable, ignoring the topic almost entirely for the first half of the century. But the last two decades have produced a flurry of new information, say University of Vermont psychologist Harold Leitenberg, Ph.D., and South Carolina's Kris Henning, Ph.D. And it turns out that a lot of what we thought we knew is wrong.

Imaginary Lovers

The misconceptions about sexual fantasies began with Freud himself. In 1908 he declared that "a happy person never fantasizes, only a dissatisfied one." Later thinkers embroidered this theme, developing what has become known as the deficiency theory.

"People still believe that fantasies are compensation for lack of sexual opportunity," says Leitenberg. "That if your sex life was adequate, you wouldn't have to fantasize."

But the data show that, if anything, frequent fantasizers are having more than their share of fun in bed. They have sex more often, engage in a wider variety of erotic activities, have more partners, and masturbate more often than infrequent fantasizers, Leitenberg and Henning report in Psychological Bulletin.

The association between fantasies and a healthy sex life is so strong, in fact, that it's now considered pathological not to have sexual fantasies.

And no wonder. Researchers studying sexual fantasies confirm that everyone has them, from adolescence onward. Well, almost everyone: About five percent of men and women say they have never had a sexual fantasy (or won't admit to it). Person believes that these fantasy-free folks are getting a vicarious fix elsewhere--from movies, for example. Or else they simply aren't paying attention to their own thoughts.

Most adults say they first remember fantasizing between the ages of 11 and 13. From there they quickly pick up speed. Sexual fantasies and thoughts are most common in hormone-addled teens and young adults. In one study, researchers asked people at random times during the day whether sex had crossed their minds during the past five minutes. Among 14- and 15-year-olds, 57 percent of boys and 42 percent of girls said yes. Affirmative responses were less common with increasing age: among 56-to 64-year-olds, 19 percent of men and 12 percent of women answered yes.

Once you get beyond age, though, it's hard to predict whether a given person has lots of fantasies. Attempts to identify a "fantasy-prone" type of individual have been woefully unsuccessful. Even religious and political views provide few clues. Conservatives have just as many fantasies as liberals--despite the fact that, according to one study, nearly half of conservative Christians feel sexual fantasies are "morally flawed or unacceptable."

The devout aren't the only ones who have mixed feelings. One in four people feel strong guilt about their fantasies, reports Leitenberg. Most of this hand-wringing "involves people who feel guilty about fantasizing while making love to their partners," he says. Even among sexually adventurous groups like college students, 22 percent of women and 8 percent of men said they usually try to repress the feelings associated with fantasy.

Guilt also strikes when fantasy and personal ideology collide. "There are people who feel that their sexual fantasies are not a part of them," Person says. "The CEO of a Fortune 500 company may have masochistic fantasies of being tied to a bed, and he might be perfectly comfortable because he sees that as respite from having to be in control; whereas some feminists are ashamed because they have masochistic fantasies and they feel that the fantasies are contrary to their political beliefs."

Such guilt exacts a heavy toll. Those who fret over their fantasies have sex less often and enjoy it less, even though the content of their fantasies is no different from those of the guilt-free.

But even unusual and "deviant" fantasies give little reason for concern in healthy individuals. It's true that we sometimes use fantasies as a springboard for later sexual hijinks. But the path from fantasy to deviance is anything but direct.

Rape fantasies, for instance, are far more common than rapes themselves. And as an extreme example, consider that only 22 percent of child molesters say they had sexual fantasies about kids before their first molestation. So unusual fantasies are a concern only when they become compulsive or exclusive, or for individuals "in whom the barrier between thought and behavior has been broken," say Leitenberg and Henning.

Exactly why your fantasies differ from those of your friends is not well understood. But theories abound. Certainly personal experience and the things we see, hear, and read about enter the mix.

External stimuli like sexy advertisements or scantily clad passersby, in fact, may be responsible for the off-noted observation that men fantasize more than women. In a sample of college students, researchers found that men fantasized or thought about sex 7.2 times a day, compared to 4.5 for women. For each sex, two of those fantasies were internally triggered. But men reported twice as many externally provoked thoughts.

Our favorite internally triggered fantasies probably attain preferred status through classical conditioning, the sane process that had Pavlov's dogs drooling at the sound of a bell. Fantasies that accompany orgasms are particularly reinforced, for instance, making them more arousing next time around. From there "we embellish them, change them," says Person. "They're like an evolving series." Scenarios that don't accompany arousal are discarded.

While the most common fantasies involve routine sex with a past, present, or imaginary partner, that's not to say that we don't occasionally give our fantasy muscles a more strenuous workout. In addition to those decidedly "vanilla" scenarios, Leitenberg and Henning describe three other primary flavors of fantasy:

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