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Does science buy male bisexuality?

        Health | Sexuality

Bedroom Science: Measuring Bisexuality
How do you measure sexual attraction?
How do you measure sexual attraction?
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Although science can't explain the interpersonal aspects of attraction that serendipitously draw people toward each other from amid a sea of strangers, it's certainly figured out how to track and quantify the less romantic stuff. To evaluate sexual orientation, researchers can collect psychophysiological data on what stimulates people's inner urges. In other words, science can verify in the most basic terms what turns us on.

Functional MRI data is allowing researchers to glimpse into how and where the brain manages arousal. Not surprisingly, titillating thoughts and material literally wash over the brain, lighting up visual processors and attention processors, as well as motivation and reward systems. Sexual orientation may also influence which parts are triggered, although scientists have yet to substantively confirm distinct differences [source: Bailey].

Currently, the main instrument for measuring sexual arousal is the plethysmograph, which is a gauge designed to capture volume expansion, such as how much people's lungs can fill with air [source: Bergner]. Penile and vaginal plethysmographs can therefore identify the amount of blood flow to the genitals in response to sexual and non-sexual stimuli (generally pornographic film clips and nature footage, respectively). Researchers typically will assess study participants' sexual orientation through self-reporting and the Kinsey scale and then compare those results to plethysmograph data and evaluate how the information matches up.

Joint studies conducted in the early 2000s at Northwestern University found two stark characteristics of male arousal. Compared to women, gay and straight men exhibit significantly more "category-specific" arousal [source: Chivers et al]. Or, what evokes male sexual excitement correlates much stronger to their stated real-world sexual preferences, whereas straight and gay women displayed more sexual fluidity, meaning they were physiologically stimulated by a range of material [source: Chivers et al]. When the Northwestern researchers replicated the experiment on a group of bisexual men, the categorical specificity remained, rather than the expect fluidity. Bisexual men, the 2005 data seemed to indicate, expressed heterosexual or homosexual arousal patterns like the rest of their male cohorts [source: Rieger, Chivers and Bailey].

In a major blow to male bisexuality, science had chipped away at any social progress that had been made toward accepting it as a valid, long-term sexual orientation. But not for long.


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