Their breakdown is simple. Men like pornography. Women like romance novels. “Men’s brains are designed to objectify females,” Ogas and Gaddam write. Since men’s only concern is with the biological fitness of women for child­bearing, everything they need to know to feel desire is visible to the naked eye: “The shapely curves of female ornamentation indicate how many years of healthy childbearing remain across a woman’s entire lifetime.” Male desire is “solitary, quick to arouse, goal-targeted, driven to hunt.” That’s why there was a nearly perfect concordance between male reports of sexual arousal and evidence of physical arousal measured by a device attached to participants’ genitals in a well-known study by the sex researcher Meredith Chivers.

By contrast, Chivers found that a lot more blood flowed to the genitals of her female subjects than their self-reports would suggest. Straight men were physically aroused by videos of straight sex, but not by videos of gay sex or bonobos mating, and their self-reports confirmed what the sensors measured. Straight women were physically aroused by every­thing, including the bonobos, but their self-reports often contradicted what the sensors measured.

Chivers’s study shed light on the failure to produce a “female Viagra”: while increased blood flow to the penis is sufficient to incite a man to sexual desire, increased blood flow alone will not produce feminine desire. Ogas and Gaddam have come up with a speculative explanation for this mind-body gap: the existence of a neural structure that, they claim, “inhabits a woman’s conscious mind and intercepts signals coming from her body, preventing them from triggering conscious, psychological arousal.” This neural structure, which the authors term the “Miss Marple Detective Agency,” was supposedly contrived by evolution to protect a woman against the risks of reckless sex and to ensure that her partner would be a “strong and decent man willing to invest in a stable, long-term, child-rearing relationship.” Miss Marple has to be satisfied before a woman can be aroused.

Ogas and Gaddam argue that romance novels and their Internet-era counterpart, “fan fiction,” dramatize the workings of female desire. Such stories feature the strong, rich, handsome, competent, socially dominant alpha men whom women need to care for their offspring, and to whom they yearn to submit. How exactly a neural structure residing in the conscious parts of the brain can be innate to a single sex is never answered. Later, the authors write that every male has a set of “female software,” and vice versa; they concede that “male fans of sexual submission porn are accessing the female submissive circuitry their brain shares with women,” which raises the question of what makes the software female if both sexes possess it.