There is a simple and surprisingly durable myth about what causes men to rape women. It goes like this: if a man is too horny, from sexual deprivation or from being constitutionally oversexed, he will lose control in the presence of an unguarded woman. Through the early days of psychology as a science, this basic assumption remained the same. When Richard von Krafft-Ebing wrote Psychopathia Sexualis (1886), he assumed that rapists suffered from either ‘priapism and conditions approaching satyriasis’ or a ‘mental weakness’ that allowed lustful urges to escape their control. It was a simple matter of hydraulics. If the pressure was too great, or the vessel too weak, a horrifying crime would burst forth.

In the early decades of the 20th century, as human sexuality became the focus of intense scientific interest, this naive model of sexual assault went unquestioned by researchers. Havelock Ellis believed that all male sexuality was violent and predatory, and therefore saw no reason to doubt that rape was a normal manifestation of masculine desire. Alfred Kinsey preferred to ignore the issue altogether, dismissing most rapes as false accusations, and doubting they did real harm anyway. Thus the hydraulic model of rape persisted until the latter half of the 20th century, when it was abruptly shattered by a deadly combination of feminist theory and empirical research. That research has brought us much closer to an understanding of why men rape. But it’s also taught us something far more useful, and almost universally overlooked: how rape can be prevented.

Let’s return to the hydraulic theory, which might have persisted even longer were it not for one particularly treacherous feature: it opened the door to victim-blaming. If sexual desire triggered rape, then a really provocative woman might inspire so much lust that even a good man would be overwhelmed. The victim became the real perpetrator: the man was effectively helpless as he punched her, wrestled her to the ground, and forced his penis into her.

This idea was seized upon by Freudians in the mid-20th century. Not only did they find it plausible that victims instigated rape, they speculated that all women secretly longed for it. Female sexuality was held to be inherently masochistic, since, as the psychoanalyst Karen Horney put it in ‘The Problem of Feminine Masochism’ (1935): ‘the content of the early sexual wishes and fantasies concerning the father is the desire to be mutilated, that is castrated by him’. On this reading, female victims unconsciously desire, if not engineer, their sexual assaults. The blame sometimes spreads beyond the victim to infect every woman in sight, as when the forensic psychiatrist David Abrahamsen argued in The Psychology of Crime (1960) that a rapist was formed by a mother who was ‘seductive but rejecting’, goaded by ‘his wife’s masculine and competitive inclinations’, and finally ‘somehow seduced into committing the crime’.

Such was the lamentable state of affairs when the feminist activist Susan Brownmiller introduced her ground-breaking feminist work on rape Against Our Will (1975) with the dictum: ‘[Rape] is nothing more or less than a conscious process of intimidation by which all men keep all women in a state of fear.’ Brownmiller dispensed with any trace of victim-blaming, and dismissed the idea that rape was the result of sexual desire. Rape was instead a political crime, committed ‘for many of the same reasons that blacks were lynched by gangs of whites’. It was a crime not of passion, but of cold premeditation, often coordinated among a group. However and wherever it occurred, the motive was not sex, but power.

This theory gained instant currency with sympathetic readers, and divided public opinion into warring camps. To anti-feminists, it was patently absurd, akin to saying burglars aren’t motivated by money, but by a twisted desire to oppress homeowners. For feminists, it was intuitively true, and incidentally useful in supporting broader arguments about gender inequality.

In 1975, research money was plentiful, and the field of psychology was enjoying a new respectability, so the stage was set for a flood of studies into the motives of rapists.

The earliest and perhaps most influential of these was undertaken by the clinical psychologist Nicholas Groth, who studied several hundred rapists at prisons and high-security mental wards throughout the Massachusetts penal system, publishing his conclusions in Men Who Rape (1979). For Groth, all rapists had one of three possible motives: sadism, anger or the desire for power. He described the psychology of these three types, asserting that rape was never the act of a mentally healthy person, but ‘always a symptom of some psychological dysfunction, either temporary and transient or chronic’. He also stated categorically that rape is ‘a pseudosexual act’, that it uses sexuality to express ‘issues of power and anger’, and that ‘It is sexual behaviour in the primary service of non-sexual needs.’

Unfortunately, Groth offers no evidence for these beliefs. He doesn’t explain how he conducted his research, or give any hint of what questions he asked his subjects. He doesn’t say how he arrived at his motivational categories, or how he came to believe that all rapists were mentally ill. His work is worth mentioning only because he’s still commonly cited as having proven rape isn’t motivated by sex. If he found any such proof, he left no trace of it in his writings.

Meanwhile, other researchers were attempting to prove the traditional, hydraulic model – and spectacularly failing. Various studies found that testosterone levels were not higher in rapists. Nor did sexual deprivation correlate with rape: the surveys conducted found that, if anything, rapists had more consensual sexual partners than other men. And, as the late Paul Gebhard and colleagues at the Institute for Sex Research (now the Kinsey Institute) showed in Sex Offenders: An Analysis of Types (1965), married rapists were just as likely to have active sex lives with their wives. These results were so consistent, regardless of the political orientation of the researchers, that the belief that rape resulted from priapism or frustration was abandoned by all sides.

At the same time, the pure version of the non-sexual theory also fell out of fashion. This was an indirect result of a change in the orientation of research. Psychologists had initially studied incarcerated rapists because they were available. But only a tiny fraction of sex offenders are ever incarcerated, and they are atypical of all men who engage in sexual violence. Convicted sex offenders are much more likely to have assaulted strangers, used a weapon, deployed unnecessary violence, and hold previous criminal records. These men are almost never college-educated professionals or well-regarded members of their communities – characteristics that we now know do not preclude men from raping.

So in the mid-1980s, a new wave of studies focused on so-called ‘undetected’ rapists – men who had never been arrested or even reported for their crimes. These men were much less likely to have used violence or even physical force. Instead, the majority had assaulted women who were incapacitated by alcohol. When they did use force, it was almost always after an attempt at consensual sex had failed, the so-called ‘date rape’. It seemed unquestionable that these men were at least partially motivated by sex.

But perhaps the most startling fact that emerged from this new research was that it was possible to find unincarcerated men who would admit to being rapists. Most of the subjects were college students, and it seems incredible that this group would confess sex crimes to total strangers. However, as long as the word ‘rapist’ didn’t appear in the questionnaire, men were comfortable answering ‘yes’ to questions such as: ‘Have you ever had sexual intercourse with an adult when they didn’t want to because you used or threatened to use physical force?’ In interviews conducted by the psychologists David Lisak and Susan Roth at Duke University in North Carolina, and later by Lisak and Paul Miller at Brown University in Rhode Island, it turned out that respondents somehow didn’t realise that this was a description of rape.

If relatively common levels of callousness, selfishness and sexism can turn a man into a rapist, the problem seems insoluble

The other startling result was how many such men there were. In 10 different studies undertaken between 1985 and 1998, between 6 per cent and 14.9 per cent of male college students (who made up the majority of respondents) admitted to rape or attempted rape, and roughly half of this number had done so repeatedly. These studies relied on a standard questionnaire, the Sexual Experiences Survey, where the phrase ‘without their consent’ (or its equivalent) appeared in every question used to determine whether a man was a rapist. All such questions referred to vaginal, anal or oral sex. Furthermore, in personal interviews, men who admitted to non-consensual sex made no attempt to claim that there had been a misunderstanding. They knew their victims were unwilling. They were just terrifyingly bad at making the connection between non-consensual sex and rape.

What such studies discovered about the character of these men was less startling. Were rapists less empathetic than other men? Unsurprisingly, yes. Were rapists more self-centred and manipulative? To no one’s amazement, yes. Did rapists have negative attitudes towards women? Unastonishingly, also yes. On all these parameters, the difference between rapists and non-rapists was small but significant. The conclusion seemed to be that rapists weren’t monsters, totally distinct from normal men, but did tend to be (to use layman’s terms) misogynist arseholes. Again, this was not earth-shattering news.

It’s also not good news. If relatively common levels of callousness, selfishness and sexism can turn a man into a rapist, the problem seems insoluble. We might conceivably end sexism, but people have been trying to root out callousness and selfishness for thousands of years with no noticeable success.

The study Understanding Sexual Violence (1990) conducted by Diana Scully for the US National Institute of Mental Health helps to point a way out of this morass. Scully compared incarcerated rapists with a control group of other felons, using an 89-page interview to measure the men on traits such as hostility toward women, interpersonal violence and ‘compulsive masculinity’. On all of these measures, rapists and other felons were indistinguishable. There was also no difference in their sex life before prison, their attitudes toward women, or their history of childhood sexual abuse.

What struck Scully most powerfully were the lengths to which the rapists went to justify their crimes to her. They talked about their victims’ moral failings. They consistently lied about details of their crimes to make themselves seem less violent. They tried to represent rape as normal; as one subject put it: ‘When you take a woman out, woo her, then she says: “No, I’m a nice girl,” you have to use force. All men do this.’ Others maintained that everyone considered it acceptable to rape a woman if she was known to be promiscuous, if she’d been picked up hitch-hiking, or if she’d had sex with the man before. Some of the interviewees admitted that they knew what they’d done was wrong; in these cases, they typically made a great deal of their self-loathing, and insisted that the crime was completely unlike them. They were, in short, remarkably concerned with what other people thought of them. It seemed clear to Scully that these considerations played a crucial role in their decisions – decisions she considered both conscious and rational – to force women into sex.

More significant still, the overwhelming majority of the men assumed that they would never be punished. As one rapist said: ‘I knew I was doing wrong. But I also knew most women don’t report rape, and I didn’t think she would either.’ As Scully put it, her subjects saw rape as ‘a rewarding, low-risk act’.

It’s worth pausing here to underscore just what this implies. For a man to commit sexual assault, he must be a relatively, but not strikingly, antisocial person – enough that he isn’t too constrained by empathy for his victims. These seem like preconditions for any crime that has a victim; and indeed, the measured character traits of convicted rapists are identical to those of muggers and burglars. But a man who is capable of rape generally commits the crime only if he believes it will be excused by his peers, and that punishment can be evaded. There seem to be a remarkable number of men who meet these criteria; most of the college-age rapists studied were not only unafraid of punishment, but blissfully unaware that what they did was criminal. Looking at this general picture, Scully concluded that most rapes are the result of a ‘rape culture’ that tells men that, in many situations, raping women is not only normal behaviour, but completely safe.

If there really is such a thing as rape culture, it follows that we should see large variations in rates of sexual violence from country to country, depending on the degree to which it is condoned or punished. To cut to the chase, we do. We might remember that 6 to 14.9 per cent of male college students in the US confessed to rape. This statistic seems terrible until you learn that, according to a study published in The Lancet, the percentage of men who self-identify as rapists in China is just under 23 per cent, and in Papua New Guinea, it’s a brutally depressing 60.7 per cent.

Sexual assault by soldiers in wartime also differs dramatically from army to army, and offers an interesting test case, because the disciplinary environment in which it occurs runs the gamut from deliberate encouragement of sexual violence to harsh and summary punishment of sexual violence.

Apparently, even in the midst of war, men are capable of refraining from sexual assault if they know there will be consequences

The resulting picture is very clear. At one extreme, we have the Rape of Nanjing ahead of the Second World War, where Japanese commanders actively incited soldiers to assault civilians, and 20,000 women were raped within the first month of the occupation. Meanwhile, incidents of sexual violence are historically low among Left-wing guerrilla groups; for instance, after the 12-year civil war in El Salvador, a UN Truth Commission report in 1981 found no reported cases of rapes being committed by insurgents, although sexual violence by government forces was common in the first years of the war. This is probably due both to the freedom of such groups to enact extra-legal punishments, and to their existential need to win the hearts and minds of the population.

Wartime rape also appears to change rapidly in response to directives from above. For instance, the notoriously high rate of sexual violence by the Red Army at the end of the Second World War decreased dramatically when the Soviet leadership decided it was a political problem, and instituted rules to discourage it. In the Salvadoran civil war, rapes by government soldiers steeply decreased once the US threatened to withdraw military aid if the government’s human-rights record didn’t improve. Apparently, even in the midst of the violence of war, men are capable of refraining from sexual assault if they know there will be consequences.

The commonsensical conclusion is that rape, like other crimes, can most effectively be prevented by deterrence. This seems obvious; which makes it only more surprising that so much energy has been devoted to avoiding preventative thinking.

The history of research into rape’s causes is a history of trying to redefine rape as something that needs a medical solution, or a political solution, or as the inevitable result of male sexuality, which cannot have any real solution: as anything but a crime that must be punished. This bias almost certainly springs from an unwillingness to acknowledge that the suffering of female victims is important enough to merit the punishment of male perpetrators. Victims’ advocates have also often failed to emphasise penal solutions, fearing that the criminal justice system is incorrigibly hostile to their concerns. Even when punishment does enter the discussion, it is usually framed as a means of obtaining justice for individual victims, rather than as a means of preventing future crimes. All the research done to date shows that this is a mistake. Even if the criminal justice system is resistant to change, that is where our efforts must be directed if we want to eradicate rape.

We must not act as if the solution for rape is a profound and unfathomable mystery

The West is clearly doing better than Papua New Guinea on this score, but there’s still ample room for improvement. According to research for the British Home Office, while on average an estimated 69,000 rapes (including attempts) are committed in the UK every year, of these only 16,000 are reported, and around 1,000 perpetrators (male and female) are brought to justice. It is worth noting that these statistics include offences committed by men and women, and against male and female victims, however the overwhelming majority of rapes are committed by men, the overwhelming majority of victims are women, and 99 per cent of those convicted of rape (and assaults by penetration) in the UK are men. In the US, only an estimated 2.2 per cent of reported rapes ever result in a conviction.

Yet we can boost conviction rates without abandoning our commitment to the rights of the accused (another common excuse for inaction). We can give police and prosecutors more funding for sexual-assault investigations, which are still woefully likely to be dropped in the early stages. We can monitor their efforts to ensure they follow best practices. We can fund the testing of forensic evidence, which is currently subject to long backlogs, and often simply lost or abandoned. Most of all, we can make it easier for victims to approach police; of all violent crimes, rape is the least likely to be reported. What we must not do is pretend it’s a different, easier problem, or act as if the solution for rape is a profound and unfathomable mystery.

With robbery, arson or fraud, we all know that punishment serves not only as retribution, but as deterrent. We grasp that, if murders go unpunished, it’s not just a matter of private conscience but a public safety issue. We understand that when we decide not to aggressively prosecute possession of marijuana, use of marijuana will increase among otherwise law-abiding people. We know that if we want to reduce identity theft, we must direct police and prosecutors to make that crime a priority, and give them sufficient funds and training to successfully convict the people involved. It’s time we applied the same common sense to rape.