Men consistently report higher levels of sexual desire than women. Differences in levels of hormones — testosterone, specifically — are believed to at least partially explain the gender divide.

Hormonal changes that occur as couples move from the passionate early stage to the compassionate later stage into monogamous relationships sometime between six and 30 months may also mediate changes in desire over time. Pharmaceutical companies are currently researching the impact of testosterone on women’s desire, but so far, the results have been inconclusive.

Hormones are only part of the story, Murray told LiveScience. “Although they are one piece of the sexual desire puzzle, focusing too heavily on hormones can remove the contextual factors that play into desire, such as whether or not a woman is in a satisfying, loving relationship, and if she has time to feel relaxed, playful and sexy,” she said.