A casual observer might take note of Darren Sharper's pending plea agreement in rape charges spread across at least four years and four different states for any number of the obvious reasons—this is, after all, a case involving a former NFL All-Pro being revealed as a serial rapist. One of those reasons, though, would clearly be the "penis monitoring" attached to Sharper's lifetime probation in Arizona, whereby instruments will be attached to his penis to measure how sexually arousing he finds various graphic images. This makes for some obvious enough jokes, but it's also based on ridiculous science.

Plethysmography as a medical function was developed nearly 50 years ago, and measures the volume of different parts of the body. Plethysmography for penises, outside of use in the judiciary system, can be used to observe possible causes of erectile dysfunction. Think of it like taking the blood pressure of a penis, but (a little) more exact. The two types in common use measure either volume or circumference. In the context of Sharper, here's how this works: The apparatus is attached to his dong, he is shown graphic sexual images, and court-appointed officials observe whether they turn him on.

There are some problems with this.

1. The science is based on bad assumptions

A large part of any scientific endeavor involves setting standards and measuring against them. Can you imagine any topic harder to standardize and score than sexual proclivities? Now imagine setting up a standardized test to test against them. These visual and audio stimuli are basically thrown together ad hoc by the states that use plethysmography, based on what the individual testing groups believe would arouse a "normal" or sexually deviant person. At best, it isn't ideal to engage the overlapping, complex sexual desires of humans and try to draw conclusions. But without a set group of stimuli to which testers can refer back, the "test" distills down to a selection of functionally random images and sounds and how hard they make someone's dick.

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Physiological differences aside, and forgetting smaller matters of taste—you might like blonde-haired women, for example, but think the lighting in a particular shot is unflattering, therefore, no boner—there is also the problem that arousal is not the same as desire. Here's a passage from the Skeptic's Dictionary with more context:

From a scientific, moral, and legal point of view, what should matter is whether a person gives in to perverse desires and commits sex crimes. It is neither immoral nor a crime to get aroused. Furthermore, being aroused is not identical to having a desire. A man or woman may be aroused by the sight of animals copulating or be aroused by a film of a woman eating a banana and a man eating a fig in particularly provocative ways. Still, they may have no desire to engage in bestiality or have sex with a bowl of fruit or have sex at all. ... There are many pedophiles who are not aroused by photos of naked children. ...

Decreased arousal may not be strong evidence for decreased tendency to engage in criminal sex acts. Strong arousal need not imply strong desire for what causes the arousal; and weak arousal need not imply weak desire. Furthermore, no test can determine whether a person will act on his feelings and desires. Nevertheless, many of those who treat sex offenders swear by the PPG even though there is no compelling evidence that PPG readings validly indicate a tendency to commit or not commit sex crimes.

This applies to cases like Sharper's, where government officials are trying to determine how likely an admitted rapist is to repeat his crimes given that he has already demonstrated that he is willing to act on desire. The issue here is that the arousing factors might be (are likely to be, actually) completely unrelated to sexual imagery. We know there's a fundamental disconnect between erotic images and sexual violence—there are many, many motivations behind sexual assault that are not uncontrollable arousal—but in the context of this science, there isn't enough information to make that distinction. What you enjoy watching and what you actually want to do are two different things. Conflating them helps no one.

2. It's also completely unreliable

Let's put rape and the line between fantasy and crime aside. Possibly, you might think, this test could be used to identify more obvious sexual deviances, like pedophillia. It doesn't, because there's very little predictive reliability in it. Here's a passage from the Transsexual Road Map's primer on plethysmography:

Bradford (1997) candidly reviews the problems in penile response in testing. He collected data from a group of 200 subjects, 100 of whom were admitted child molesters and 100 of which were volunteer "community control" subjects. Even using an admitted population of child molesters, Dr. Bradford's penile tumescence testing could only correctly classify 62% of the admitted homosexual child molesters and 52% of the admitted heterosexual child molesters. According to the report, twenty-five (25%) accuracy in classification would have been expected from mere chance.

Other studies report that plethysmography has an even poorer accuracy record. Simon & Schouten cite a study (Wormith) in which 42% of the pedophiles were classified as having normal sexual preferences. Another study they cite (Barbaree and Marshall) found that only 35% of pedophiles demonstrated the "pure" child-preference profile (Simon 1993, at 508). See also McAnulty 1990.

The primary concern, according to Bradford, "is the external validity of the procedure, or the extent to which the assessment of sexual preference in the laboratory predicts behaviour outside the laboratory" (Bradford 1997).

Those are not good results for a test that is part of a court-ordered probation program. But that's not even the most ridiculous part of using this as a reliable diagnostic. It turns out that people are pretty good at not getting boners when they need to be:

The largest and most unresolved problem with using measurements of penile response as a diagnostic or classification tool is the fact that penile response can be controlled by test subjects. "The problem of faking, more than any other, continues to limit the clinical utility of phallometric tests" (Schouten 1992).

In one test, researchers made the "striking and somewhat unexpected finding [of] the ability among 80% of the subjects who exhibited sexual arousal to the stimuli to later voluntarily and completely inhibit sexual arousal." (Hall 1988) Of Hall's 122-member test group, 114 were able to reduce their response, 91 were able to completely inhibit response and only 4 were unable to reduce their arousal. Problems of accuracy in classification increase when the test is used with a non-admitting population because response is subject to voluntary control and the test is therefore vulnerable to faked response.

So, a full 80 percent of participants were able to will their dongs into tricking this test.

3. It has a bad, bigoted history

Probably naturally, the idea that you can determine what arouses a person has grabbed the attention of those fixated on knowing exactly who is gay, and perhaps (or thus) in need of fixing. The modern use of the technology originated in 1950s Czechoslovakia, where Kurt Freund invented it as a screening tool, meant to test men who were trying to get out of the army on claims of being gay. Later, it would be used as a way to screen for "gender variance."

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This is where it's concerning that this sort of test is still associated with the court. With no set standard—and no way to come up with one that would work anyway, because the underlying test is junk—it's a simple rhetorical turn to map behavioral profiles onto sexual preferences. Another passage from the Transgender Road Map:

The real long-term issue with Bailey and Blanchard is "thought crime" described by Orwell in 1984 or "future crime" described by Philip K. Dick in "The Minority Report." Their claims about the predictive value of neurometrics sound a lot like phrenology revisited.

Bailey, Blanchard, and Lawrence embrace a model in which gender variance is associated with sex offenses, criminality, mental illness, and lying. Blanchard asks in one paper "what defect in a male's capacity for sexual learning" could cause gender variance (Blanchard 1991). This parole officer mentality permeates their theories and methods, which are carried out under the assumption that those who agree with them are "honest and open" (Bailey 2003, 147) or "unusually candid" (Lawrence 1998). Those who disagree are lying.

When challenged by transsexual women, they frequently try to discredit critics by accusing them of deception. In his widely denounced book, Bailey quotes a Blanchard employee who asserts that "most gender patients lie" or "provide misleading information" (Bailey 2003, 172-175). Bailey also attempts to dismiss scientific criticism as "political correctness" (Pinnel 2003) or "identity politics" that are "a hindrance to scientific truth" (Bailey 2003a). He claims that "there is good scientific evidence that you should believe me and not them" (Dreier 2003).

Freund's research did lead him to attempt "conversion therapy" on his patients in Czechoslovakia, but he eventually came to the conclusion that it was useless; even gay men who had married women did not show signs of becoming attracted to them. He eventually lobbied for homosexuality to be accepted, and for conversion therapy to be discontinued, due to its inefficacy and fundamental category error.

This has not stopped his methods from finding other homes.

4. Arizona is mandating U.S. citizens undergo treatment once used as a gay "cure"

Back to Sharper. Here's how penile plethysmography works in the "rehabilitation" of sex offenders, as of 1993:

A subject may be exposed to stimuli depicting as many as twelve different sexually stimulating fantasies. A complete set of twelve audio presentations might consist of six consenting and six nonconsenting situations. Additionally, each of these sets of sexual situations might cover the full range of child, adolescent, and adult targets for both genders. Some operators supplement the audio presentation by briefly showing three or four slides of nude persons of different ages and gender.

For child sex offenders, there's the added problem of trying to "stimulate" subjects without using confiscated child porn, which was necessarily created by exploiting kids.

Visual stimulus materials depicting individual, nude children of various ages and sex need not be exploitive and are more appropriate for assessing an offender's sexual preferences. Audio stimulus materials can be effective in depicting explicit sexual acts and can be used with fewer legal and ethical objections. No one is exploited in using audio materials.

Presumably, rapists are not shown actual footage of sexual assaults caught on some sort of surveillance, but reenactments which are necessarily staged and therefore, however realistic, created as erotica. This isn't a semantic point; it's definitional. Agencies create "stimuli," more commonly referred to as pornography, for use in demonstrably unscientific and inaccurate tests, and judge reactions of the test subjects based on, among other things, how well their clinically-developed porn films match up to ingrained preferences. Forget that there is a logic gap the length of an Xvideos tag separating arousal from desire from action; this is fundamentally compromised data by design.

Yet this is then acted upon, in Clockwork Orange-style gay-conversion fashion. Here's a description of how child sex offenders are treated:

Aversive conditioning using noxious odor and masturbatory satiation are among the procedures used in some of these programs. Recent research supports the efficacy of aversive conditioning in reducing deviant sexual arousal in juvenile sex offenders. The plethysmograph is used in 27% of the juvenile sex offender programs, Thirty-sex percent of the 726 adult sex offender treatment programs use the plethysmograph.

Think about this for a moment. This treatment—strapping a person into a machine that force-feeds them pornography and then "punishes" sexual stimulation associated with those images—is so far outside the scope of how you'd envision modern legal recourse, and so far into revenge fetishization, that it's impossible to imagine it applied outside of the narrow way we define and react to sex crimes. Effective or otherwise, it is an attempt at reconditioning a person's sexual identity away from its natural state, functionally turning the government's focus on a person's thoughts instead of his actions, which are punishable by methods more in the confines of the Eighth Amendment. Inquisitional methods like these, seen as necessary for sex offenders—a class of criminal subjected to lifetime punishment, something we don't even extend to murderers—would be dismissed prima facie as barbaric science fictions if a state ever attempted to apply them to the pleasure centers of a serial burglar, or an attempted murderer, or a con artist, or a shoplifter.

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Darren Sharper will serve his probation in Arizona, where his dick will be monitored at court-ordered intervals. He's a public figure whose overlapping, identical rape cases make him as unsympathetic a figure as possible. But it shouldn't be lost that Arizona's interest in his penis is not some dick-joke gag tacked onto the end of his sentence. It's just bad science in a state rotten with the stuff.

Top photo via AP