Of Human Violence

The Saint Bartholomew's Day Massacre by François Dubois.

THE WORLD HEALTH ORGANIZATION defines VIOLENCE as: [18]

"The intentional use of physical force or power, threatened or actual, against oneself, another person, or against a group or community, which either results in or has a high likelihood of resulting in injury, death, psychological harm, maldevelopment, or deprivation."

The SOCIAL ECOLOGICAL MODEL is often used to study the effects of violence; as well as to determine the effectiveness of prevention strategies. The model is comprised of 4 levels: [18-20, 33]

Image source: www.cdc.gov

INDIVIDUAL LEVEL: Identifies biological and personal factors that influence how individuals behave and increase their likelihood of becoming a victim or perpetrator of violence: demographic characteristics, genetics, brain lesions, personality disorders, substance abuse, and a history of experiencing, witnessing, or engaging in violent behavior.   

RELATIONSHIP LEVEL: Focuses on close relationships, such as those with family and friends.

COMMUNITY LEVEL: Explores the community context: schools, workplaces, and neighbourhoods.

SOCIETAL LEVEL: Looks at the broad societal factors that help to create a climate in which violence is encouraged or inhibited: the responsiveness of the criminal justice system, social and cultural norms regarding gender roles or parent-child relationships, income inequality, the strength of the social welfare system, the social acceptability of violence, the availability of weapons, the exposure to violence in mass media, and political instability.

STATISTICS

• According to 2010 statistics from the  Global Burden of Diseases, Injuries, and Risk Factors Study, suicide accounted for about 883,000 of all violent deaths; interpersonal violence (between individuals) for 456,000 and collective violence (between larger groups of individuals) for 18,000. [24] 

• According to the Global Study on Homicide, prepared by the UN Office on Drugs and Crime, the 2012 percentage distribution of homicide victims by age and sex were as follows: [25]

• 8% Females aged 15-29

• 13% Females not aged 15-29

• 35% Males aged 15-29

• 44% Males not aged 15-29 

• Approximately 20% of women and 5–10% of men report being sexually abused as children, while 25–50% of all children report being physically abused. [27]

• Recent global prevalence figures indicate that 35% of women worldwide have experienced either intimate partner violence or non-partner sexual violence in their lifetime. [28]

• In chimpanzee society, the males are usually the violent gender. 

• Based on the compiled statistics I came across on this subject (government & non-government agencies), the same seems to hold true for human populations. [31]

• The U.S. Department of Justice sponsored a National Crime Victimization Study in 2007. This evaluation found that 75.6% of all offenders were male and only 20.1% were female. In the remaining cases, the victim wasn't able to identify the gender of the offender. [26][32] 

EVOLUTION

Most animals use aggressive displays to ward off competitors for food or mates without the intention of causing serious injury or death. Two notable exceptions to this general rule are humans and chimpanzees. [31]

Scientists have observed chimps forming raiding parties along the borders of their own territories. A group of male chimps will patrol, searching for members of neighboring groups. If they find one, they may attack with violent ferocity, injuring or even killing their victim. [31]

Research exploring the root causes of this behaviour was recently published in the journal, Nature. The study found that a majority of violent attackers and victims of attack were male chimpanzees. This information is consistent with the theory that these acts of violence are driven by adaptive fitness benefits rather than human impacts. [30]

"Wild chimpanzee communities are often divided into two broad categories depending on whether they exist in pristine or human disturbed environments. In reality, however, human disturbance can occur along a continuum and study sites included in this investigation spanned the spectrum. We found human impact did not predict the rate of killing among communities.” [30]

In the 1997 paper, Human Aggression in Evolutionary Psychological Perspective, authors Buss and Shackelford suggested 7 adaptive problems our ancestors recurrently faced for which aggression might have evolved as a solution: [21][23]

1. Co-opting the resources of others;
2. Defending against attack;
3. Inflicting costs on same-sex rivals;
4. Negotiating status and hierarchies*
5. Deterring rivals from future aggression;
6. Deterring mate from infidelity;
7. Reducing resources expended on genetically unrelated children.

*In his review [22][23] of research on the evolutionary psychology of violence, Goetz writes of how some seemingly trivial dispute can quickly escalate, ultimately resulting in homicide when there is a status dispute between two unrelated human males of relatively equal status.

• However, if there is a great initial status difference, then the lower status individual usually offers no challenge. And even if he does, his challenge is usually ignored by the higher status individual.  

TESTOSTERONE

Is there a connection between testosterone and violent behavior? 

If the 1993 classic The Program taught us anything, it's that the answer to that question is a resounding, yes!

• Castration experiments have demonstrated that testosterone is necessary for violence. [3] 

• From Frank McAndrew, professor of psychology at Knox College in Galesburg, Ill: [3]

"From what we can tell now, testosterone is generated to prepare the body to respond to competition and/or challenges to one's status. … Any stimulus or event which signals either of these things can trigger an increase in testosterone levels." 

In a 2008 study, published in the American Journal of Public Health, young adult males who used anabolic steroids (a synthetic version of testosterone) reported greater involvement in violent behaviors than those who did not use steroids. [2]

HOWEVER, just because testosterone is necessary for violence, doesn't necessarily mean its presence is a predictor of violent behaviour:

• In a 2000 study, large doses of testosterone (600 mg/wk) increased manic symptoms in only a small proportion of normal male participants. [2]

• And in one game theory study, researchers told several female participants that they were receiving the dose of testosterone when in fact they were in the placebo group.

• Interestingly, these same participants then proceeded to play unfairly, attributing their behaviour to the effect of the testosterone. Whereas the participants who had (unknowingly) actually received the dose of testosterone played with more honesty and generosity. [1]

PSYCHOPATHS

Nearly 1 in 5 violent offenders exhibits the traits of a psychopath, a personality disorder characterized by a lack of empathy, no remorse, manipulative behavior, and extreme selfishness. MRI’s reveal that psychopathic violent offenders have abnormalities in the parts of the brain related to learning from punishment. [4][5]

TORTURE [6]

“More than 50 years ago, Yale University psychologist Stanley Milgram proved through a series of obedience experiments that the conflict of personal conscience diminishes when an authoritative figure is introduced because weight of responsibility is lifted from the person and placed on the authority.” [6]

 “Certain brain regions (particularly the anterior insula) activate when you experience a negative emotion or pain, and also when you see someone else experience the same emotion or pain. Your brain experiences another’s pain as if it were your own.”  — The ‘golden rule’ effect. [7]

So the question is: In terms of violence in the form of torture, is the latter point—more often than not—overruled by the former?

Following the release of the Central Intelligence Agency’s Detention and Interrogation Program Report—a report that told how inhumane tactics including water-boarding, prolonged sleep deprivation, forced feeding and sensory deprivation, were used by interrogators to extract information—a national survey released by Pew Research Center  indicated that 51% of Americans surveyed believed the CIA methods were justified, while 29% said they were not. [6]

*(Worth noting here that despite my having used an American example, well, let’s just say glass houses, stones and all that.)

GENETICS & BIOCHEMISTRY

Selective breeding has demonstrated that it is possible to select for genes that lead to more aggressive behavior in animals. [8][9]

Serotonin, Dopamine, Norepinephrine  and neurotransmitter metabolizing enzyme MAO-A have been the focus of much violence/aggression research. [10]

[1] SEROTONIN

• In one mouse study, when mutants were made by deleting a gene for the serotonin receptor: [11]

• Mutant males attacked intruders with twice the intensity of normal male mice.

• Mutant males reared alone showed a strong tendency to attack other males upon their first exposure to the other animals.

[2] DOPAMINE

• In a 2008 study investigating variants of the DAT1 (dopamine transporter), DRD2 (dopamine receptor) and MAO-A genes, researchers found that:

• In all three cases, the variants of these genes were associated with an elevated risk of violent and delinquent behavior ONLY in people who experienced certain stresses during childhood. [13]

[3] NOREPINEPHRINE

• In this 2011 study on the mechanisms of aggression, the authors hypothesize that the chemical(s) responsible for inducing aggressive behavior must fulfill the following criteria: [36]

(i) when released in the organism or injected in physiological doses, it elicits/amplifies aggressive behavior;  

(ii) its synthesis and release increases during stress and agonistic encounters; 

(iii) its basal concentration in dominants is higher in brain structures responsible for aggressive behavior.

• The study found that norepinephrine best fit the above criteria: it stimulates an aggressive response and is produced actively when aggressive behavior is necessary for adaptation. 

[4] NEUROTRANSMITTER METABOLIZING ENZYMES: MONOAMINE OXIDASE A (MAO-A) 

• The enzyme monoamine oxidase A (MAO-A) affects the neurotransmitters dopamine, norepinephrine and serotonin. [35]

• Particular variations in the X-chromosome gene that produces MAO-A, (The Warrior Gene) have been shown to cause a syndrome that includes violence and impulsivity in humans. [10][12][35] 
• The variants, known collectively as MAOA-L, produce only a low level of the functional monoamine oxidase A enzyme. [35]

Video clip:  VIOLENCE: NATURE OR NURTURE?

[Via National Geographic]

• Research published in the journal, Neuro-psychopharmacology (2007) investigated violent criminality in 184 adult male volunteers referred for forensic assessment by looking at: [16]

• MAOA genotype
• Serotonin transporter (5-HTT) genotype
• Dopamine transporter (DAT) genotype
• Adverse childhood environment

• The study found that:

• 45% of violent males carried the short (low-activity) MAOA allele.

• Independent of childhood experiences, the short (low-activity) MAOA allele increased the risk to commit violent crime.

• However, that this common polymorphism conveys ONLY a statistical predisposition toward a certain behaviour is reinforced by the fact that 30% of the non-violent males also carried short MAOA alleles. 

 (ASIDE: An fMRI study demonstrated that this at-risk genotype results in amygdalar hyper-reactivity in response to emotional arousal, paralleled by impaired response of prefrontal brain regions including the anterior cingulate cortex. [17]) 

• Homozygotes (possessing 2 identical alleles for a particular gene) for the long serotonin transporter (5-HTT) allele were generally less likely to develop later-life aggressive behavior, whereas short allele homozygotes behave the opposite way.

• Only 5-HTT heterozygotes (possessing 2 different alleles for a particular gene) were influenced by environmental factors. 

• A DAT variation was NOT shown to play a role in the disposition toward violence.

• A 2014 Finnish study [34]  showed that Finnish criminals convicted of several violent crimes frequently possessed either MAOA-L or a mutant version of another gene, CDH13* while the nonviolent controls did not. [35]

• *CDH13 is involved in signaling between cells. Previous research has linked it with attention deficit/hyperactivity disorder (ADHD), autism, schizophrenia, substance abuse or bipolar disorder. [35]

• In the United States, court defense has been successful in reducing sentencing for violent offenders by calling blameworthiness into question on account of certain genetic predispositions. [14][15]

Et Finalement

From Bad to the Bone: Are Humans Naturally Aggressive? (2012) by Agustín Fuentes Ph.D. 

While we know that certain parts of the brain interact with certain neurotransmitters and a range of steroid hormones to produce aggressive behavior, "we also see that there is no specific physiological or neurological system designed for aggression.  Everything involved in the expression of aggression is tied to other systems and its use in behavior is highly contextual. There is no consistent system or pattern in the human body or mind that we can point out as the seat or the main actor in aggressive behavior." [29]

In other words

“Human nature is complex. Even if we do have inclinations toward violence, we also have inclination to empathy, to cooperation, to self-control.”    

Steven Pinker 

***

FIN

REFERENCES

[1] http://www.nature.com/scitable/blog/cognoculture/testosterone_and_human_aggression_or_180520

[2] https://www.psychologytoday.com/blog/the-human-beast/200907/sex-violence-and-hormones

[3] http://www.scientificamerican.com/article/strange-but-true-testosterone-alone-doesnt-cause-violence/

[4] http://www.medicaldaily.com/signs-psychopath-least-violent-kind-include-inability-learn-punishment-319624

[5] Gregory S, Blair RJ, ffytche D, et al. Punishment and the psychopath: an fMRI investigation of reinforcement learning in violent antisocial personality disordered men.Lancet Psychiatry. 2015.

[6] http://www.medicaldaily.com/cias-torture-reports-and-psychology-human-torture-what-makes-person-capable-torturing-3144540

[7] Sood, Amit MD, Mayo Clinic The Mayo Clinic Guide to Stress Free Living (2013)

[9] Nelson, Randy Joe (ed.) (2006). Biology of Aggression. Oxford: Oxford University Press. ISBN 0-19-516876-3.

[10] Tremblay, Richard E., Hartup, Willard W. and Archer, John (eds.) (2005). Developmental Origins of Aggression. New York: The Guilford Press. ISBN 1-59385-110-3.

[11] Bock, Gregory R. and Goode, Jamie A. (eds.) (1996). Genetics of Criminal and Antisocial Behavior. Chichester: John Wiley & Sons.ISBN 0-471-95719-4.

[12] Caspi A, McClay J, Moffitt T, Mill J, Martin J, Craig I, Taylor A, Poulton R (2002). "Role of genotype in the cycle of violence in maltreated children". Science 297 (5582): 851–4.doi:10.1126/science.1072290. PMID 12161658.

[13] Maggie Fox. Study finds genetic link to violence, delinquency. Reuters, Jul 14, 2008.

[14] http://en.wikipedia.org/wiki/Nature_versus_nurture

[15] Halwani, Sana; Krupp (2004). "The Genetic Defense: The Impact of Genetics on the Concept of Criminal Responsibility".Health Law Journal 12: 35–70. PMID 16539076.

[16] http://www.nature.com/npp/journal/v32/n11/full/1301359a.html

Andreas Reif, Michael Rosler, Christine M Freitag, Marc Schneider, Andrea Eujen et al.   Nature and Nurture Predispose to Violent Behavior: Serotonergic Genes and Adverse Childhood Environment Neuropsychopharmacology (2007) 32, 2375–2383; doi:10.1038/sj.npp.1301359; published online 7 March 2007

[17]Meyer-Lindenberg A, Buckholtz JW, Kolachana B, Hariri AR, Pezawas L, Blasi G et al (2006). Neural mechanisms of genetic risk for impulsivity and violence in humans. Proc Natl Acad Sci USA 18: 6269–6274. | Article |

[18] http://www.cdc.gov/violenceprevention/overview/social-ecologicalmodel.html

[19] Patrick, C. J. (2008). "Psychophysiological correlates of aggression and violence: An integrative review". Philosophical Transactions of the Royal Society B: Biological Sciences 363(1503): 2543–2555. doi:10.1098/rstb.2008.0028.PMC 2606710. PMID 18434285.

[20] McCrory, E.; De Brito, S. A.; Viding, E. (2012). "The link between child abuse and psychopathology: A review of neurobiological and genetic research". JRSM 105 (4): 151–156.doi:10.1258/jrsm.2011.110222. PMID 22532655.

[21] http://homepage.psy.utexas.edu/homepage/group/busslab/pdffiles/human%20aggression-1997-clin%20psych%20rev.pdf

[22] Goetz, A. T. (2010). "The evolutionary psychology of violence".Psicothema 22 (1): 15–21. PMID 20100422.

[23] http://en.wikipedia.org/wiki/Violence

[24] Lozano, R; Naghavi, M; Foreman, K; Lim, S; Shibuya, K; Aboyans, V; Abraham, J; Adair, T; Aggarwal, R; Ahn, SY; Alvarado, M; Anderson, HR; Anderson, LM; Andrews, KG; Atkinson, C; Baddour, LM; Barker-Collo, S; Bartels, DH; Bell, ML; Benjamin, EJ; Bennett, D; Bhalla, K; Bikbov, B; Bin Abdulhak, A; Birbeck, G; Blyth, F; Bolliger, I; Boufous, S; Bucello, C et al. (Dec 15, 2012). "Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010". Lancet 380 (9859): 2095–128.doi:10.1016/S0140-6736(12)61728-0. PMID 23245604.

[25] http://www.unodc.org/documents/gsh/pdfs/2014_GLOBAL_HOMICIDE_BOOK_web.pdf

[26] United States Department of Justice

[27] WHO, "Child maltreatment", 2014.

[28] WHO, "Violence against women", 2014.

[29] Bad to the Bone: Are Humans Naturally Aggressive? Post published by Agustín Fuentes Ph.D. on Apr 18, 2012 in Busting Myths About Human Nature

[30] Lincoln Park Zoo. "Nature of war: Chimps inherently violent; Study disproves theory that 'chimpanzee wars' are sparked by human influence." ScienceDaily. ScienceDaily, 17 September 2014. <www.sciencedaily.com/releases/2014/09/140917131816.htm>.

[31] Strickland, Jonathan.  "Why are we violent?"  20 September 2010.  HowStuffWorks.com. <http://science.howstuffworks.com/life/why-are-we-violent.htm>  18 April 2015.

[32] Strickland, Jonathan.  "Are men more violent than women?"  13 September 2010.  HowStuffWorks.com. <http://science.howstuffworks.com/life/men-more-violent.htm>  18 April 2015.
[33]  Dahlberg LL, Krug EG. Violence-a global public health problem. In: Krug E, Dahlberg LL, Mercy JA, Zwi AB, Lozano R, eds. World Report on Violence and Health. Geneva, Switzerland: World Health Organization; 2002:1–56.
[34] http://www.nature.com/mp/journal/vaop/ncurrent/full/mp2014130a.html
[35] http://www.geneticliteracyproject.org/2014/11/04/does-the-human-warrior-gene-make-violent-criminals-and-what-should-society-do/ 
[36] http://www.sciencedirect.com/science/article/pii/S1359178911000255

RESOURCES

http://www.brainyquote.com/

Nature × nurture: Genetic vulnerabilities interact with physical maltreatment to promote conduct problems

IMAGE CREDITS

"Francois Dubois 001" by François Dubois - [1]. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Francois_Dubois_001.jpg#/media/File:Francois_Dubois_001.jpg

"Tereo" by Peter Paul Rubens - Unknown. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Tereo.jpg#/media/File:Tereo.jpg