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The Explosive Mix of Sex and Violence

The sexual assaults in Cologne reveal a connection between sex and violence.

Key points

  • A mass celebration can inflame extreme mob behavior resulting in the victimization of women.
  • Some past violent attacks on women were both sexually and criminally motivated by men in environments where such brutality went unchecked.
  • Rape is less frequent if social alliances exist to combat it.
photo by the author
The risk of sexual assault and violence increase in crowds
Source: photo by the author

The roving gangs of men who sexually assaulted women during the New Year’s Eve celebration in Cologne, Germany, have ignited outrage across Europe and around the world. (1) The political implications have been much discussed, but how was this violence triggered in these individuals? These assaults illuminate a dark side of human nature: how sex and violence are interlinked in the human brain.

A perplexing link between human sexual behavior and violence is evident from an early age when boys tease and punch girls (2) they are attracted to. Some major league baseball players look at pornography right before they go to the plate to increase their level of aggression. Thirty percent of all internet traffic is pornography, and 88 percent of this contains physical aggression. (3) In the extreme, sadistic sexual behavior can develop from the intertwining of sex and violence in the human brain. As crowds grow and become unruly, especially if alcohol and other drugs are involved, gang sexual assault can erupt with awful spontaneity.

Biologically, sex and violence share a number of common brain states and functions. Both behaviors evoke intense arousal—indeed, the most intense states of arousal possible. Fighting and mating share some of the same neural circuits, neurotransmitters and hormones of arousal, and both activities strongly stimulate the brain’s reward and pleasure systems. This brain circuitry can lead men to seek out violence, to pick fights for no apparent reason other than to derive satisfaction from the rewarding feeling that comes from the shot of dopamine in the brain accompanying aggression. This is the same neurotransmitter boost produced by cocaine and other drugs of addiction. The neurotransmitter serotonin is also involved in both sexual gratification and in violence. (4)

The biological underpinning for this intersection between sex and violence is a nasty legacy of our primate ancestors. Many animals, nonhuman primates among them, use violence to obtain and defend mates. Both aggression and sex are controlled by neurons in the same part of the brain--the hypothalamic attack region. When researchers stimulate these neurons with electrodes in the brains of mice, the animals instantly engage in violence or in mating, depending on how strongly the neurons are stimulated.(5) The abrupt switch between mating and fighting is completely under the control of the researchers who can flip the animal from mating to fighting by stimulating these neurons at the right intensity. It is an unsettling observation.

The violence of sexual assault combines freely with other crimes of violence because sex and violence satisfy the same psychological and neurobiological mechanisms that underlie all crimes of violence. Frequently sexual assault is not sexually motivated; it can stem purely from aggression, rage, and dominance. Sexual assault is a crime of extreme violence, combining elements of robbery, destruction, and cruel brutality using sex as a weapon. In wartime, sexual assault of women takes place in horrifying numbers—for example, the 276 school girls abducted as sex slaves by Muslim extremists Boko Haram in Nigeria;(6) an estimated 20,000 to 200,000 women forced into prostitution by Japan during World War II in "comfort stations";(7) and an estimated 2 million German women raped by Soviet soldiers during World War II.

Violence against women is hardly limited to these extreme situations, however. Nearly 20% of all women in the U.S. have been sexually assaulted.(8) The alarming statistics on sexual violence against women cut broadly across all walks of life. A 2014 study,(9) for example, found that 20% of female scientists were victims of sexual assault in the workplace. However, the anonymity and chaos of large crowds increase the risk of sexual assault on women, even on a crowded subway, but a mass celebration can inflame extreme mob behavior victimizing women. Mob violence is stimulated by the intense arousal from sensory stimulation, and the heightened stresses of being buffeted in a noisy, frenzied crowd. Mob behavior is driven by the strong herding instinct of people to do as they see others do when there is no central authority in control.(10) At the opposite extreme, this same powerful herding instinct can cause bystander apathy in which no one in a crowd comes to the aid of a person in need. Tribal identity triggers an “us-vs-them” perception that fuels violence in gangs, barroom brawls, in mobs, and sometimes mêlées between immigrants and residents.

In the recent assaults in Germany, groups of 30-40 men formed spontaneous gangs surrounding women, robbing and brutalizing them sexually. Similar attacks on women have occurred at Mardi Gras celebrations in Seattle,(11) at out-of-control drunken parties on college campuses, and even at US military conventions, as when 83 women were sexually assaulted by a hundred US Navy and Marine Corps officers in Las Vegas in 1991 in the Tailhook scandal.(12) These diverse incidents suggest an uncomfortable conclusion. Violent attacks on women are both sexually and criminally motivated by groups of men in an environment where such animal brutality went unchecked.

Rape is less frequent if social alliances exist to combat it. About 88% of orangutan matings in the wild involve aggressive attacks by males that force the females into submission.(13) Female orangutans are solitary, whereas female gorillas are protected from this level of violence because they live in well-structured troupes that provide mutual protection from aggressive males. A person’s experience during rearing influences these brain circuits. This is why children raised in an environment where domestic violence occurs will be more likely to exhibit those same behaviors as adults. This is also why, as is evident in many places around the world, social environments that tolerate sexual aggression and violence against women create a vicious vortex that drives sexual brutality against females.

The majority of those committing the sexual assaults in Cologne, Germany are reported to be men from countries where sexual violence against women is a disturbing social problem. These recent attacks resemble the horrific assault of CBS news correspondent Lara Logan by groups of frenzied men in Tahrir Square during celebration of the downfall of Egypt’s Dictator Hosinni Mubarak in 2011.(15) On the one-year anniversary of this celebration, nearly 90 women were brutally sexually assaulted in Tahrir Square again by roving gangs of men.(16)

This problem must be faced head-on. To skirt uncomfortable facts about these assaults out of political concerns or to blame victims will perpetuate the problem. The mix of cultures brought us Tex-Mex cuisine, and the delightful flavors and sounds of New Orleans, but this also brought smallpox to Native Americans. The outbreak in Cologne is not a new disease, but the universal outrage it provokes shows the strong commitment in civil society to stamping it out. It is important to recognize the biological factors that increase the danger of sexual violence in mass celebrations and ensure adequate crowd control, but anyone who would sexually assault a woman must be severely punished whether the perpetrator is a despised immigrant in a mob or a beloved personality on TV.


1. Jordans, F. Cologne divided over who to blame for New Year’s assaults. TIME Jan. 6, 2016

2. Martin C. Signs that a guy is about to ask you out. Dating Tips

3. Staff Reporter, Porn sites get more visitors than Netflix, Amazon and Twitter Combined, The Huffington Post, May 4, 2013.…

4. Nelson, R. J. and Chiavegatto, S. Molecular basis of aggression, Trends in Neurosciences 24, December 2001: 713-19.

5. Lin, D., et al., Functional identification of an aggression locus in the mouse hypothalamus. Nature 470, February 2011, 221-26.

6. Melvin, D. Boko Haram kidnapping of 200 Nigerian schoolgirls, a year later. CNN, April 14, 2015.

7. Olivo, A. Homage to WWII comfort women puts Fairfax in a delicate situation. The Washington Post, May 31, 2014.

8. National Intimate Partner and Sexual Violence Survey, 2010

9. Clancy, KBH, Nelson, RG, Rutherford JN, Hinde, K. Survey of Academic field experiences (SAFE): Trainees report harassment and assault. PloS ONE 9 e102172 (2014).

10. Raafat, R.M., Chater, N., Frith, C. (2009) Herding in humans. Trends in Cognitive Sciences, vol. 13, p. 420-428.

11. Death, rape and rage at Seattle’s Mardi Gras: A radical woman’s response, Radical Women, March 23, 2001.

12. Davis, K., Tailhook’s whistle-blower talks sexual assault. Navy Times June 11, 2013.…

13. Peterson, D., Wrangham, R. Demonic Males: Apes and the Origins of Human Violence, Houghton Mifflan, Company, New York, (1997)

14. Mayen, N. Women in Egypt suffer more sexual violence under Islamist rule. Al Arabiya News, October 18, 2014.…

15. Logan, L. Lara Logan breaks silence on Cairo assault. 60 Minutes, May 10, 2011.

16. Eltahawy, D. Amnesty International, Livewire, July 3, 2013.…

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