Both men and women have sexual fantasies, though -- perhaps not surprisingly -- the types of things they fantasize about differ.

Researchers at the University of Granada have released the results of a study which found that women fantasize about "pleasant" sexual encounters a few times a month, while men fantasize much more frequently and about more "exploratory" sexual activities including group sex, "being promiscuous," "being a swinger," and "participating in an orgy."

The study included responses from 2,250 Spanish people between the ages of 18 and 73 who had been in a heterosexual relationship for at least six months.

Nearly all of the respondents reported that they had fantasized about a "pleasant" sexual experience, while 80 percent said they had fantasized about an "unpleasant" one.

A commonly reported unpleasant sexual fantasy among the women surveyed was “being forced to have sex," the study revealed. This fantasy had occurred at least once in most of the female participants' lifetimes.

For men, the most commonly reported "unpleasant" sexual fantasy was a homosexual encounter.

While the University of Granada report did not go into specifics regarding how often these fantasies occur, previous studies have shown men think about sex every seven seconds.

Dr. Logan Levkoff, a HuffPost blogger, previously wrote that having sexual fantasies is part of a healthy lifestyle and that a woman's sex life isn't complete without them.

"Other than our skin, our brains are the biggest sex organ we have," Logan wrote in January. "We are supposed to use them. We are supposed to have an active fantasy life. Sexual fantasies do not make us sluts. Nor do they suggest that we have trouble in our current relationship. Fantasies make us healthy sexual beings."

Dr. Diana Hoppe, a California-based OB/GYN physician, has also stated that it can be healthy for women to connect with their sexuality through fantasizing about sex.

"A woman's libido is a reflection of her overall health, and a healthy sex drive not only indicates a well-balanced life, but also has health benefits," Hoppe told the San Francisco Business Times. "A healthy libido equals a healthy you."