During our expansive exploration of sexual desire, we encountered a number of popular erotic interests that defied academic predictions and evolutionary theory. For example, among heterosexual men, the stunning popularity of shemale porn (sometimes referred to as futanari), incest porn, and bukkake porn, three of the most searched for erotic genres in the world. Among women, slash fan fiction (romantic and erotic male-male stories), incest stories, and the phenomenal global popularity of paranormal romance, whose leading example is Stephanie Myers’ Twilight novels.
As computational neuroscientists, we turned to the design of the brain to attempt to explain these prevalent yet baffling erotic tastes. In particular, we considered the operation of “sexual cues,” hardwired sexual taste predispositions analogous to our hardwired gustatory tastes. Just as our brains come hard-wired with five different taste cues—salty, sour, sweet, savory, bitter (some researchers add metallic and fat), our brains also come hard-wired with a finite set of sexual cues. However, though male and female brains share the same taste cues, our brains come loaded with entirely different sets of sexual cues. It’s as if the male brain has salty and sour cues, and the female brain has bitter and sweet cues. If we each tasted the sexual equivalent of peanut brittle, a man would report a salty flavor while a woman would report its sweetness.
In previous computational neuroscience research, we had modeled how the brain manufactured optical illusions, such as the enigmatic Mona Lisa smile, by simultaneously juxtaposing two different visual cues to create a strange and beguiling gestalt that was perceptually “more than the sum of its parts.” (In the case of the Mona Lisa smile, da Vinci juxtaposed a low-frequency grin with a high-frequency flat expression to produce the beguiling smile that seems to appear or disappear depending on where your eyes come to rest on the painting.)
Our brain can also be tricked by gustatory illusions: restaurants like Chili’s and T.G.I.Friday’s hire food engineers who craft culinary concoctions that combine different gustatory cues (salty, fatty, sweet, crunchy) into irresistible gustatory illusions that promote what the food industry calls cravability, such as Chili’s Texas Cheese Fries or Cheesecake Factory’s Oreo Dream Extreme Cheesecake.
It appears that our brains might also be tricked by erotical illusions. By combining (or distorting) multiple sexual cues into novel gestalts, it’s possible to evoke bewilderingly intense sexual arousal. Male erotical illusions are mostly visual, since the male sexual brain consists primarily of visual cues. Female erotical illusions are mostly psychological, since the female sexual brain consists primarily of psychological cues.
Erotical illusions account for one of the most popular and baffling sexual interests of heterosexual men: shemale porn. (Many transsexuals find the term “shemale” offensive when applied to an individual, though this is the common term for the genre within the adult industry.) Figures in shemale porn feature the body of a woman and a penis, often a large one.
In Japanese anime, transsexual characters are known as futanari. Futanari porn reveals exactly what appeals to straight men about shemales. Futanari characters are drawn with hyperfeminine bodies, typically very young, with large round breasts and hourglass figures, large eyes with long eyelashes and beautiful faces. They also possess giant horse-sized penises. Typical futanari features schoolgirls with giant protrusions beneath their plaid skirts, teenage girls with pink hair and a bulge in their jeans, slender ballerinas in tutus and sporting erections as long as their slender legs.
Recently, contemporary adult webmasters have found ways to manufacture “artificial shemales” that do not involve the use of actual transsexual actresses. The women are voluptuous and curvy, with enormous strap-on dildos that look like authentic if colossally oversized penises. The site is full of scenes of attractive, busty women stroking their giant artificial manhood.
The site makes the erotical illusion very clear: anatomical cues of femininity juxtaposed with the visual cue of a penis. (The penis is a prominent sexual cue for many heterosexual men.)
What about the opposite? What about someone with strong muscular arms, tattooed biceps, a bald head, a beard—and a vagina? The most famous transsexual male porn star is the cigar-puffing Buck Angel.
Buck Angel combines a number of visual cues of masculinity with the single feminine cue of a vagina. Straight men express no interest in Buck Angel, and some find him disquieting. But many gay men find him extremely intriguing. The sexual brains of most women, however, do not respond to Buck Angel as a visual erotical illusion. Instead, erotical illusions comprised of psychological cues are more effective at tricking the female sexual brain—such as paranormal romance.
Some of the psychological cues that consistently appear in the hundreds of thousands of female-authored erotic stories and the thousands of digital romance novels we analyzed include heroes who are alpha males (strong, confident leaders), intelligent and experienced, willing to protect women from physical harm, desired by many women (though they only love the heroine), who lust intensely after the inexplicably irresistible heroine, who hide a secret tender side, and whose aggressive nature is tamed by the heroine’s love. It turns out that these cues are all whirled together and amplified in the stories of paranormal romance.
Consider Edward Cullen, the vampire hero of Twilight. Since he is a vampire, he has the body of a 17-year old hotty—but the experienced, mature mind of a 107 year old. He is the ultimate alpha: an immortal warrior dispatches human bullies with ruthless ease, rescuing Bella Swan time and again. All the girls at Bella’s high school have crushed on Edward—but he is only interested in Bella, because of her inexplicably delicious smell. He lusts after Bella—literally, since he lusts after the blood coursing through her veins—but demonstrates his love for Bella by not acting on his primal urge to rip open her neck and drink her blood. Cullen is an Oreo Extreme Dream Cheesecake for the female sexual brain: a superalpha who eternally lusts after one uniquely special woman, but who forever demonstrates his kind and loving heart by not acting upon his savage impulses—at least, not when he’s around his beloved; he’s free to release his barbaric side when challenged by villainous opponents.
Unlike women, men are not aroused by romantic stories of vampire women with youthful bodies and elderly minds. The male sexual brain does not process the same sort of literary erotical illusion.
Erotical illusions make vivid one of the most fascinating aspects of human sexuality: that much of sexual arousal results from the integrative sorcery of our imagination.