THE CAUSES OF VIOLENCE
- 2010/02/19 15:38:57
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John Monahan, Ph.D.
Psychologist and Professor
School of Law
University of Virginia
I have been asked to summarize everything that we really know about the
biological, sociological, and psychological causes of violence--in 20 minutes or
less. Unfortunately, I think I can do it.
But, I warn you in advance what I cannot do--what no one can honestly do--and
that is to offer a neat, simple story that explains why so many Americans are
afraid to walk home alone at night. Only people on the extremes of the political
spectrum have that luxury and that conceit.
The political right believes that the root cause of violent crime is bad genes
or bad morals. Not so, says the left. The root cause of violent crime is bad
housing or dead-end jobs. And, I tell you that while doing something about the
causes of violence surely requires a political ideology, the only way we can
determine what those causes are in the first place is to check our ideologies
at the door and to try to keep our minds open as wide, and for as long, as we
I realize that this is not easily done. But, if you give it a try, which I
urge you to do, I think that you will find that violence does not have one root
cause. Rather, violence has many tangled roots. Some grow toward the left and
some grow toward the right. We have to find the largest ones, whichever way they
grow,and only then can we debate how to cut them off.
First, the biological causes. These are the easiest to talk about, because
there is not much to say.
Many biological factors have been nominated as candidates for causes of
violence. Hormones like testosterone, transmitters in the brain like serotonin,
and blood abnormalities like hypoglycemia are only a few that have been
Biological factors do not have to be hereditary. They could be caused by a
head injury, poor nutrition, or environmental events, such as exposure to lead
Fortunately, the National Academy of Sciences just reviewed hundreds of
studies on the relationship between biology and violence, and it came to one
clear bottom-line conclusion: "No patterns precise enough to be considered
reliable biological markers for violent behavior have yet been identified." (1)
The National Academy of Sciences found many promising leads that should be
vigorously pursued by researchers, but so far, it could point to nothing as a
proven, or even close to proven, biological risk factor for future violence.
Next come the sociological causes. We know the most about social factors and
violence, because social factors, such as demography, are relatively easy to
measure and because people have been measuring them for a long time. What do we
know? We know a great deal about a relatively small number of things.
We know that to live in America is to live in the land of the brave, as well as
in the home of the free. We are all familiar with depressing statistics about
the U.S. trade deficit with Japan. But more depressing is this Nation's crime
surplus.Compared with Japan, a nation of roughly comparable industrialization,
with cities much more crowded than ours, the U.S. homicide rate is over 5 times
higher, the rape rate is 22 times higher, and the armed robbery rate is an
astounding 114 times higher. (2)
We also know that within America, violence is subject to great regional
variation. The murder rate, for example, is almost twice as high in the South as
it is in the Northeast, but the robbery rate is almost twice as high in the
Northeast as it is in the South. (3)
We know that communities within all regions of America differ drastically
among themselves in how violent they are. In general, the smaller the community,
the lower the rate of violence. Within the same city, some neighborhoods have
rates of violent crime 300 times higher than other neighborhoods. (4)
We know that people who commit violence on the street are disproportionately
poor and unemployed. Prior to their arrest,jail inmates had, on the average, an
annual income at the Federal Government's official "poverty level," and about
one-half were unemployed at the time they committed a violent crime. (5)
We know that the overwhelming majority--close to 90 percent--of the people
arrested for crimes of violence are men and that despite enormous changes in
gender roles in recent decades, this figure has not budged for as long as
criminal records have been kept. (6) Indeed, there is no place in the world
where men make up less than 80 percent of the people arrested for violence, now
or at any time in history. (7)
We know that violence is primarily the work of the young.People in their
late teens and twenties are much more likely to be arrested for violence than
younger or older people. (8)
We know that the arrest rate--and the victimization rate--for violent
crime for African-Americans is now about six times higher than for whites. (9)
Finally, we know that official violent crime rates, as high as they are,
drastically underestimate the actual rate of violence in America, particularly
violence within the family. (10)
After this, what we know about the sociological correlates of violence
falls off rapidly. Note that I said "correlates," not "causes."
Two problems keep us from knowing which factor really matters as a cause of
violence and which is irrelevant. One problem is that each factor relates not
only to violence but to other sociological factors as well. Call this the "ball
of wax" problem. Poverty and race, for example, are related not just to violence
but also to each other. If poverty is taken into account, the effect of race on
violence decreases drastically, and in some studies, disappears entirely.
The second problem is that it is sometimes hard to tell which came first,
the sociological factor or the violence. Call this the "cause and effect"
It is true, of course, that violence does not cause people to be male or to
be young. But it is not clear whether unemployment leads people to commit
violent acts or whether, for at least some people, their violent acts lead
employers to not want to hire them. It is also possible that, at least for
some people, a third factor--like an "impulsive" temperament--causes them both
to be violent and to be unlikely to keep a steady job. (11)
Finally, the psychological causes. If research on violence were like stock on
Wall Street, then I would put my money right now on psychology. By this, I most
emphatically do not mean mental disorder. The best epidemiological evidence
indicates that major mental disorder accounts for, at most, 3 percent of
the violence in American society. (12)
What I mean, instead, are the developmental processes that we all go
through, most of us more or less successfully, but some of us with great
difficulty. I mean particularly the family (13) --the filter through which most
of the sociological factors,such as a parent's being unemployed, and many of
the biological factors, like poor nutrition, seem to have their effect on a
child growing up.
There is a risk, of course, that whenever someone talks about families and
children, that person invokes images that may never have existed, except perhaps
on 1950's television. And, even if these images did once exist, they surely no
longer reflect the great variety of relationships in contemporary America.
But, whether we prefer Ozzie and Harriet Nelson or Murphy Brown, there is
one important thing we should not forget. That is, all types of families share
something in common. Whether they are married or cohabitating, biological or
adoptive or foster, single or dual, gay or straight, and whatever their
ethnicity, virtually all parents try to raise their children to be neither the
victims nor the perpetrators of violence.
Fortunately, most families, whatever their type, succeed. Unfortunately,
FAMILY, CHILDREN, AND VIOLENCE
What do we know about families and children and violence?
We know that while many aggressive children go on to be law-abiding adults,
aggression at age 8 significantly predicts violent convictions well into the
thirties, in every culture in which it has been studied. (14)
We know that most children who have been physically abused by their parents
go on to be perfectly normal adults. Yet, physical abuse doubles the risk that a
boy will have convictions for violent crime as an adult. (15)
We know that failure of a child in school is one of the most enduring
correlates of later violence. Four out of five violent offenders in prison never
finished high school. (16)
We know that stability matters. The more changes of placement a foster
child experiences while growing up, the more likely that child will later be
arrested for a violent crime. (17)
We know that lack of parental supervision has been consistently related to
delinquency, including violent delinquency. One study, for example, found that
10 percent of nondelinquents were poorly supervised by their parents,
one-third of one- and two-time delinquents were poorly supervised, and
over three-quarters of repeat offenders were poorly supervised. (18) Another
study found that for children growing up in very disadvantaged and violent
neighborhoods, who look like they have everything going against them, the one
factor that seems to protect that child from growing up to be violent is having
a parent--overwhelmingly, a mother--who supervises her child very strictly and
who nips misbehavior in the bud, rather than waiting for the principal to call
or the police officer to knock on the door. (19)
Finally, we know much about the relationship between illegal drugs and
violence. But it is important to remember that the connection between one legal
drug--alcohol--and violence is beyond dispute. About one-third of all violent
offenders are alcoholic, and the earlier an adolescent starts to drink, the more
likely that teen will be violent as an adult. (20)
These findings are not immune from either "ball of wax" or "cause and
effect" problems. Failure in school, for example, is associated not only with
violence but also with poor parental supervision. And, it is not obvious whether
frequent changes of placement for a foster child leads to violence, or whether
a child's violence at home leads foster parents to give the child back to the
agency. But surely, the accumulated findings provide reason to believe that
families have an enormous influence, for better or worse, on how children
None of these findings in any way negates the influence of social
conditions in giving rise to violence. Poor people, for example, without
adequate child care, may have a much more difficult time monitoring their
children's behavior than affluent people with live-in help.
Nor do the findings necessarily negate the possible influence of biological
factors. Nutrition, to give another example, is something that parents literally
put on the table for the child to eat. But it is through the family that these
things have their effects and through the family that those effects might best
We know some important things about violence, particularly about the home
environment and violence. But, we do not know early enough about how to prevent
violence in the first place or how to stop it from happening again once it
begins. How can we learn more, so that 10 years from now, it will take a bit
longer to summarize the field?
LEARNING ABOUT VIOLENCE
We can learn more if we do four things. We need to 1) make along-term
national investment in research and development, 2) have a coherent and
coordinated Federal strategy for studying violence, 3) implement a comprehensive
and inclusive violence research agenda, and 4) institute a program of
rigorously evaluated interventions to reduce violence.
LONG-TERM NATIONAL INVESTMENT IN RESEARCH AND DEVELOPMENT FOR A SAFER AMERICA
It takes resources to isolate the biological, sociological, and psychological
factors that are associated with violence, to untangle the ball of wax in
which they are found, and to determine which are the causes of violence and
which are its effects. The National Academy of Sciences just did an audit and
concluded that the Federal Government spends a total of $20 million a year on
violence research, which works out to about $3 per violent victimization. (21)
Researchers always say that more money is needed for research. But let me
point out that the Nation's budget for research on violence is considerably less
than one-half what the Federal Government will spend this year on mohair
price subsidies. (22) Nothing against goats, but a shortage of fuzzy sweaters is
not what is keeping people behind locked doors at night.
A COHERENT AND COORDINATED FEDERAL STRATEGY FOR STUDYING VIOLENCE
Organizational responsibility for research on violence is spread across a number
of Federal agencies- the National Institute of Justice, the National Institute
of Mental Health, the National Science Foundation, the Centers for Disease
Control, and several smaller programs. (23) Surely, we do not need a "violence
czar" to provide central management of the Nation's research on violence. But we
do need to be sure that all bases are covered and that there is a forum where
innovative ideas can be shared and followed up quickly.
Partnerships with private foundations may be particularly cost-effective.
The collaborations between the MacArthur Foundation and the National Institute
of Justice in funding the Program on Human Development and Criminal Behavior and
between the MacArthur Foundation and the National Institute of Mental Health in
funding the MacArthur Risk Assessment Study are exciting examples of strategic
leveraging of public and private resources. (24)
A COMPREHENSIVE AND INCLUSIVE VIOLENCE RESEARCH AGENDA
The agenda needs to promote the three kinds of research I mentioned--biology,
sociology, and psychology. It has to study them not in isolation from one
another but together as different pieces of the same puzzle.
The time is ripe to give some priority to studying developmental influences
and the effect of the family environment on violence. But this has to include
health-related and biological factors that are mediated through the family, as
well as social and psychological influences. You cannot paint a full, life-like
picture of the causes of violence if you mark a corner of the canvas
ideologically off limits before you start painting.
A PROGRAM OF RIGOROUSLY EVALUATED INTERVENTIONS TO REDUCE VIOLENCE
This goes to the top of the agenda. We will finally understand the causes of
violence when we can take a group of children at high risk of becoming violent
and ethically offer them opportunities and services to defy our predictions.
The interventions should be intensive and broadly based in practice, but
initially, small-scale in scope. We simply do not know enough to mount major
national programs to attack the causes of violence, even if we had the money to
do so. But we certainly do know enough to start trying many things in a
completely voluntary way, without unnecessarily labeling anyone, and see what
One modest idea is derived from the research on child rearing that finds
parental supervision so important in preventing crime and violence. Taking a cue
from studies like this, we could offer an intensive, long-term,
state-of-the-art education program to a random group of parents whose children
are enrolled in Federal child care programs. (26) This program would teach
parents how to effectively monitor their children's behavior, how to recognize
potentially serious misbehavior when it occurs, and how to consistently,
but fairly, discipline their children in response to misbehavior. (27)
If this worked, if children whose parents received the program had lower
levels of aggression and other social problems when compared to a control group,
we could gradually expand the program, rigorously evaluating its effects each
step of the way. If it did not work, we would go back to the drawing board,
roll up our sleeves, and try something different.
A dozen ideas like this--none of them panaceas--could be derived from
research on children and families and tried simultaneously in different parts of
the country. If even a few of them worked, we would have taken a giant leap
forward in violence prevention.
The short of it is that first, we need to make a national scientific commitment
to understand the causes of violence. Once this happens, we need to make a
national political commitment to do something about them.
[Webmaster's Note: The solution is too simple. Put God back in the classrooms.
When the children believe there is no God, there is no reason to love their
(1) A. Reiss and J. Roth, eds., Understanding and Preventing Violence
(Washington, DC: National Academy Press,1993), 116.
(2) T. Westermann and J. Burfeind, Crime and Justice in TwoSocieties:
Japan and the United States (Pacific Grove, CA: Brooks/Cole, 1991).
(3) R. Nisbett, "Violence and U.S. Regional Culture,"American
Psychologist, 48, 1993, 441-449.
(4) Supra note 1, p. 88.
(5) Bureau of Justice Statistics, Report to the Nation on Crime and
Justice, 2d ed. (Washington, DC: U.S. Department of Justice, 1988), 49.
(6) Supra note 1, p. 72.
(7) J. Wilson and R. Herrnstein, Crime and Human Nature (NewYork: Simon
and Schuster, 1985).
(8) A. Blumstein, J. Cohen, J. Roth, and C. Visher,Criminal Careers and
"Career Criminals" (Washington, DC: National Academy Press, 1986).
(9) Supra note 1, p. 71.
(10) J.Weis, "Family violence research methodology and design," in Family
Violence, L. Ohlin and M. Tonry, eds.(Chicago, IL: University of Chicago Press,
(11) See J. Monahan and L. Walker, Social Science in Law:Cases and
Materials, 3d ed. (Westbury, NY: Foundation Press,1994).
(12) J. Monahan, "Mental disorder and violent behavior: Perceptions and
evidence," American Psychologist, 47, 1992,511-521.
(13) R. Loeber and M. Stouthamer-Loeber, "Family factors as correlates and
predictors of juvenile conduct problems and delinquency," in Crime and Justice:
An Annual Review of Research, vol. 7, M. Tonry and N. Morris, eds. (Chicago, IL:
University of Chicago Press, 1986), 29-149.
(14) D. Farrington, "Childhood aggression and adult violence: Early
precursors and later-life outcomes," in TheDevelopment and Treatment of
Childhood Aggression, D. Pepler and K. Rubin, eds. (Hillsdale, NJ: Erlbaum,
(15) C. Widom, "The Cycle of Violence," Science, 244, 1989,160-166.
(16) Supra note 5, p. 48.
(17) Supra note 1, p. 243.
(18) G. Patterson and M. Stouthamer-Loeber, "Thecorrelation of family
management practices and delinquency,"Child Development, 55, 1984, 1299-1307.
(19) H. Wilson, "Parenting in Poverty," Journal of SocialWork, 4, 1974,
(20) Supra note 1, p. 185.
(21) Supra note 1, p. 345.
(22) Budget of the United States Government-Fiscal Year1993 (Washington,
DC: Government Printing Office, 1992), Appendix One-349.
(23) Supra note 1, p. 349.
(25) E. Mulvey, M. Arthur, and N. Reppucci, "The prevention and treatment
of juvenile delinquency: A review of the research,"Clinical Psychology Review,
13, 1993, 133-167.
(26) E. Zigler and S. Styfco, eds., Head Start and Beyond: A National
Plan for Extended Childhood Intervention (New Haven,CT: Yale University Press,
(27) M. Gottfredson and T. Hirschi, A General Theory of Crime (Stanford,
CA: Stanford University Press, 1990).
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