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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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Suggested Citation:"SUMMARY." National Research Council. 1993. Understanding and Preventing Violence: Volume 1. Washington, DC: The National Academies Press. doi: 10.17226/1861.
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SUMMARY 1 SUMMARY In cities, suburban areas, and even small towns, Americans are fearful and concerned that violence has permeated the fabric and degraded the quality of their lives. The diminished quality of life ranges from an inability to sit on the front porch in neighborhoods where gang warfare has made gunfire a common event to the installation of elaborate security systems in suburban homes where back doors once were left open. Children in urban schools experience violence on the way to school and in the school building itself. Surveys show that large percentages of the population fear even walking in their neighborhoods at night. The nation's anxiety on the subject of violence is not unfounded. In 1990, more than 23,000 people were homicide victims. Violent deaths and incidents that result in lesser injuries are sources of chronic fear and a high level of concern with the seeming inability of public authorities to prevent them. In 1988 the National Academy of Sciences was asked by a consortium of federal agencies—the National Institute of Justice, the National Science Foundation, and the Centers for Disease Control—to assess the understanding of violence, the implications of that understanding for preventive interventions, and the most important research and evaluation needed to improve understanding and control of violence. In response, the Academy created the Panel on the Understanding and Control of Violent Behavior. This volume presents the panel's findings, conclusions, and recommendations;

SUMMARY 2 Volumes 2, 3, and 4 contain the background papers the panel commissioned to facilitate its work. The panel adopted as its definition of "violence": behaviors by individuals that intentionally threaten, attempt, or inflict physical harm on others. Death is the basis for defining the most serious violent crime—murder. However, with murder as with lesser acts of violence, the definition masks enormous diversity in underlying behaviors that cause death: shootings by robbers, intrafamily murders, minor disputes that turn violent, sexual attacks, and gang killings. This diversity is also masked in statistical classifications of nonfatal violent crimes such as assault, robbery, and forcible rape. Even greater diversity is seen in violent behaviors that may not be counted as crimes, such as school fights, violence among prison inmates, and violence in the home. Other violent events involve large collectives: wars, state violence, riots, and some activities of organized crime. The panel did not attempt to analyze such collective violence in this report. MEASURING VIOLENCE Violent behaviors that society identifies as crimes are counted more completely and classified more accurately than those that are not. Three national measurement systems are of primary importance in counting crimes and their victims. The National Crime Survey (NCS) asks all persons age 12 and over in a national sample of households to recall and describe recent nonfatal victimizations. The Uniform Crime Reporting (UCR) system records basic information about crimes detected by or reported to police, supplementary information about homicides, and descriptions of arrestees. Homicide data are also tabulated annually from death certificates by the National Center for Health Statistics (NCHS) vital statistics program. While murders are counted rather accurately, counts of nonfatal violent crimes are incomplete. Gaps and discrepancies occur because victimizations may not be recognized as crimes, because embarrassment or psychological stigma inhibits reporting, because victims are sometimes reluctant to involve authorities, because their consequences may not be thought worth reporting as crimes, and because of discretion in classifying and counting violent events. Moreover, definitions of violent events as criminal or not change over time and differ among segments of society. Data are even less adequate for violent acts that authorities and the public are coming to recognize as serious crimes. Recent attention to bias

SUMMARY 3 crimes, for example, highlights the inadequacy of crime information on violence motivated by differences in ethnic status, religion, and sexual preference. A 1990 law requires modification of the UCR to improve statistics on bias crimes. Similarly, physical and sexual assaults against women and children by intimates and acquaintances are now increasingly recognized and reported as crimes. If all such events were included in official counts of assaults and rapes, those counts would increase substantially. PATTERNS AND TRENDS Nearly one-third of the 19 million crime victimizations reported to the NCS in 1990 involved violence. The prototype violent crime is an assault. Aggravated assaults—those with weapons or causing serious nonfatal injury—accounted for nearly 300 of every 1,000 violent victimizations. Less serious simple assaults accounted for more than 500. Robbery accounted for most of the rest. Forcible rapes accounted for about 20 in every 1,000; fewer than 4 in every 1,000 violent victimizations resulted in death for the victim. These basic patterns raise several questions: Is the United States More Violent than Other Societies? In general, the answer is yes. Homicide rates in the United States far exceed those in any other industrialized nation. For other violent crimes, rates in the United States are among the world's highest and substantially exceed rates in Canada, our nearest neighbor in terms of geography, culture, and crime reporting. Among 16 industrialized countries surveyed in 1988, the United States had the highest prevalence rates for serious sexual assaults and for all other assaults including threats of physical harm. Is the United States More Violent Today than Ever Before? No. The national homicide rate has peaked twice in this century; each peak was followed by a decline. The first peak was in the early 1930s and the rate then fell for the next 30 years. More recently, the national homicide rate began to increase in 1973 and peaked between 1979 and 1981, declining until 1984 and 1985. The homicide rate has since increased and is now at about its 1980 level. Historical data suggests that certain cities may have experienced still higher homicide rates during the nineteenth century. What is true is that, as a result of population growth, today's

SUMMARY 4 homicide rates per 100,000 residents produce total numbers of homicides that are high by historic standards. Levels of nonfatal violent crimes also rose during the late 1980s, although there is less consistency in trends across cities. Only for aggravated assault do 1990 rates exceed 1980 rates in cities of all sizes. Who Is at Greatest Risk of Violent Victimization and Death? Demographic minorities. In 1990, blacks were 41 percent and Hispanics 32 percent more likely than whites to be victims of violent crime. Ethnic differences combine with age and gender patterns so that recently young black males have been about 20 times more likely than older white females to be victimized. Homicide rates are also highest for minorities: the black rate is 5 times the white rate, and rates for Native Americans about double the rate of the entire population. Death rates from natural causes are generally low for young persons. Correspondingly, accidents and homicides become leading causes of death at younger ages. However, because minority homicide risks are high at all ages, only about one-fourth of the lifetime homicide risk for black and white males and females is experienced before the twenty-fifth birthday. American Indian males also have higher homicide victimization rates than white males, but they are more concentrated at later ages. What Are the Consequences of Violent Crimes? Although the public naturally focuses on death or injury as the outcome of violent crime, injury occurs in only about one-third of violent crimes. Most injuries are minor with only about half requiring any medical treatment and 4 percent requiring an overnight hospital stay. The victim is killed in fewer than 4 of every 1,000 violent crimes. However, the fact that 23,000 people died as a result of homicide in 1990, and that these deaths occurred in only a small percentage of violent encounters, should emphasize the magnitude of the total violence problem. Even when death or injury is avoided, losses to victims and society are sizable: an estimated average cost of $54,000 per attempted or completed rape, $19,200 per robbery, and $16,000 per assault. About 15 percent of these costs are financial—victims' monetary losses, society's costs for lost productivity, emergency response, and administration of compensation. Roughly 85 percent reflects values imputed for nonmonetary losses, such as pain,

SUMMARY 5 suffering, the risk of death, psychological damage, and reduced quality of life. Responses to violence by law enforcement, criminal justice, and private security agencies add additional costs. Additional losses, which have not been estimated but are very visible, include the destruction of families and neighborhoods; the fortification of schools, homes, and businesses; and the deterioration and abandonment of community resources such as parks and playgrounds. Who Commits Violent Crimes? We know less about the perpetrators of violent crimes than about their victims. However, we do know that offenders and their victims share similar demographic profiles. That is, they are overwhelmingly male (89% of all those arrested) and are disproportionately drawn from racial and ethnic minorities. Arrestees for violent crimes are somewhat older than victims. Men in the 25-29 age range were more likely to commit violent crimes in 1988 than any other age group. Perpetrators were acquaintances of their victims in a majority of simple assaults, forcible rapes and homicides, but in only 38 percent of aggravated assaults and 26 percent of completed robberies. One quarter of nonfatal violent victimizations are committed by multiple offenders; almost half of robberies involve co-offenders, whereas forcible rapes and simple assaults are generally solitary crimes (only 8% of rapes and 19% of simple assaults involve more than one assailant). About 8 percent of robberies involve groups of four or more. Are Violent Crimes the Work of "Violent Career Criminals"? No. While a few individuals commit violent crimes frequently, they account for a small share of total violence in the United States. Despite occasional media reports to the contrary, "serial murderers" are responsible for only about 1 or 2 percent of homicides in any year. Most recorded violent crimes occur in the course of long, active criminal careers dominated by property offenses, so that arrests for violent crimes account for no more than 1 in 8 of all arrests in European and American cohorts whose records have been analyzed. The general pattern is that while few offenders begin their criminal careers with a violent crime, most long arrest records include at least one. It is inaccurate, however, to portray this as an "escalation" from property to violent crimes.

SUMMARY 6 More generally, predictions of future violent behavior from past arrests are highly inaccurate. What Effect Has Increasing the Prison Population Had on Levels of Violent Crime? Apparently, very little. However, the question cannot be answered unambiguously. While average prison time served per violent crime roughly tripled between 1975 and 1989, reported levels of serious violent crime varied around the level of about 2.9 million per year. Estimates of the crime control effects of incarceration—by isolating violent offenders from potential victims in the community and by deterring others from committing violent crimes—are necessarily imprecise. However, if tripling the average length of incarceration per crime had a strong preventive effect, then violent crime rates should have declined in the absence of other relevant changes. While rates declined during the early 1980s, they generally rose after 1985, suggesting that changes in other factors, including some of those discussed in Part II of this report, may have been causing an increase in potential crimes. Why did average prison time served per violent crime increase so substantially between 1975 and 1989? Experience varied somewhat by crime type and state, but the data point to general increases in both the average time served if incarcerated and the chance of imprisonment if arrested. There is currently active discussion by public officials of further increases in prison sentences as a means of crime control. Analyses suggest that a further increase in the average time served per violent crime would have an even smaller proportional incapacitation effect than the increase that occurred between 1975 and 1989. According to the best estimates available to us, a 50 percent increase in the probability of incarceration would prevent twice as much violent crime as a 50 percent increase in the average term of incarceration. Achieving such an increase in certainty would, however, require substantial improvement in crime reporting and investments in police investigation and prosecution. This analysis suggests that preventive strategies may be as important as criminal justice responses to violence. The success of preventive strategies depends, however, on understanding how individual potentials for violent behavior develop, of what circumstances are conducive to violent events, and of what social processes foster violence. While the complex interactions among

SUMMARY 7 these processes are still poorly understood, careful evaluations of promising interventions are contributing knowledge that increases the ability to prevent violence. INDIVIDUAL POTENTIALS FOR VIOLENT BEHAVIOR Psychosocial Perspectives Aggressive childhood behaviors correlate with elevated potentials for adult violent behavior. However, of young children who display aggressive behavior patterns, little is known about why a few become violent adults while most do not. The distinguishing factors may be related to socioeconomic status because adult violent behavior is so much more concentrated than aggressive childhood behavior in lower-income neighborhoods. Identifying the relevant characteristics of communities, families, and persons should be of highest priority in future research. Factors associated with aggressive behavior provide a useful starting point. Modern psychological perspectives emphasize that aggressive and violent behaviors are learned responses to frustration, that they can also be learned as instruments for achieving goals, and that the learning occurs by observing models of such behavior. Such models may be observed in the family, among peers, elsewhere in the neighborhood, through the mass media, or in violent pornography, for example. Research suggests that several early childhood behaviors may be predictive of adult violent behavior. Sociable, spontaneous, and relatively fearless behavior in early childhood (an uninhibited or fearless temperament) may be a risk factor for later aggression and violence, especially in children with low socioeconomic status, whereas fearfulness may act as a protective factor against aggression. Temperament may explain why only a proportion of children from high-risk homes and neighborhoods develop antisocial or violent behavior. Adult violent offenders tend to have shown certain personality features as children. They are high on hyperactivity, impulsivity, and attention deficit, tend to be restless and lacking in concentration, take risks, show a poor ability to defer gratification, and have low empathy. They also tend to have particularly low IQ scores. Other predictors in children, their families, and surroundings include abnormally frequent viewing of violence on television, bullying in the early school years, harsh and erratic discipline, abuse or neglect, lack of parental nurturance, low income

SUMMARY 8 in large families, criminal behavior by family members, early-grade school failure, peer rejection, poor housing, and growing up in a high-crime neighborhood. Among protective factors that appear to reduce the chance of childhood aggressive behavior are a shy temperament, high IQ, being firstborn, and a small, stable family characterized by low discord. Preventing Childhood Aggressive Behavior Interventions that have shown some success in reducing children's aggressive behavior include: • social learning and cognitive behavioral interventions with elements that emphasize the undesirability of aggression, nonaggressive methods of solving interpersonal problems, social skills training, and watching television programs that emphasize prosocial behavior and • interventions such as tutoring by peers or specially trained high school students to reduce early-grade school failure. • Evaluations of these interventions with young children require long-term follow-ups to see if they reduce violent behavior at later ages. Psychosocial preventive interventions will be more successful if implementation involves parents, teachers, and significant others in the community. Sexual Violence Many psychosocial, biological, and cultural phenomena have been suggested as potential causes of sexual violence, by which we mean the threat or use of physical force either to coerce another person to submit to sexual behavior or to produce sexual excitement or release in the perpetrator. Incidents of sexual violence are more difficult to count and analyze than are most other violent incidents. Under our definition, sexual violence includes a wide range of acts. Societal responses to those acts—as criminal, deviant, or culturally acceptable—have varied over time and across cultures. Response also hinges on circumstances. Where it is clear that the act is not consensual—as in assaults on strangers or children—it is usually treated as criminal or deviant. Most violent sex acts, however, involve acquaintances or intimates, and here the designation as violent depends on whether the act occurred under coercion

SUMMARY 9 or freely given consent. Consent can be interpreted differently by one or both of the participants and may be exceedingly difficult for a third party to ascertain. Attempts to explain sexual violence, especially against strangers, have usually centered on individual differences. Among those that are not supported by available evidence are mental retardation, epilepsy, XYY or XXY chromosomal syndromes, and the use of pornography portraying consenting adults. Individual characteristics that may be involved and should be more thoroughly investigated include exposure to abnormally high testosterone levels during fetal development, abnormal testosterone levels and functioning, and genetic processes. In addition, studies of known sex offenders suggest that the following characteristics may be predictive: psychosocial and neurobiologic factors with respect to aggression generally, sexual abuse during childhood, chronic alcohol abuse, and the use of pornography that depicts violent attacks on women. Finally, clinical research suggests that a contributing factor may be violent sexual preferences, learned through experiences around the time of puberty, in which sexual arousal and release provide the reward for fantasies about violent acts. However, research on these characteristics is not conclusive as they are not found in all identified sexual assaulters and their prevalences among sex offenders have not been compared with those in the general population. Of the available preventive interventions, behavioral treatment of offenders using aversive stimuli such as electric shock has shown mixed results, and several states have banned this approach. Assertiveness training, anger management, life skills training, and relapse prevention are more widely used but have rarely been rigorously evaluated outside institutions. Situational prevention strategies suggest installing video cameras, alarms, and emergency telephones in high-risk locations for sexual violence against strangers. Explanations offered for sexual violence against acquaintances and intimates tend to emphasize beliefs about appropriate sex roles that encourage sexual violence. Although some surveys report that disturbingly high proportions of males as young as junior high school age subscribe to various justifications for forcible rape, the causal implications are unclear because there is no available evidence on whether men who engage in violent sexual behavior hold these attitudes more widely than men who do not. Promising strategies for reducing the level and harms of sexual violence against acquaintances include socializing males about nonviolent, fulfilling sex roles and responsibilities toward women,

SUMMARY 10 teaching females ways to recognize the risks and to protect themselves, separating offenders and the intimates they repeatedly attack (e.g., by incarcerating offenders or sheltering victims outside the home), and repairing the physical and psychological consequences of sexual assault victimization. Systematic evaluations are needed of interventions that implement these strategies. Violence in Families Intrafamily violence is substantially underreported—because of traditional privacy surrounding family life, because the member composition of what makes up a family is changing, because the psychological trauma involved inhibits reporting, and because authorities have only recently begun to treat it as a crime. Nevertheless, about 6 percent of violence victims who reported to the NCS in 1990 were attacked by members of their own family—somewhat less than two- thirds were simple assaults (Bureau of Justice Statistics, 1992: Appendix 3, Table 3). The nature and severity of attacks differ significantly by sex, age, and relationship. Women are the most frequent victims of simple assaults, with divorced, separated, and cohabiting women at greatest risk. Intrafamily violence accounted for at least 18 percent of all homicides in 1990 (Federal Bureau of Investigation, 1991:13). With respect to homicide, although women are at greater risk of spousal homicide than men, a majority of family homicides do not involve spouses. Fathers, sons, and especially brothers are more likely to be killed by family members than their female counterparts. Violence toward children includes homicides, as well as physical and sexual assaults, for which national incidence and prevalence estimates are not regularly published. Children under age 4 are more likely to be killed than older children. Infants and small children are more likely to be killed by their mothers than their fathers. Female children are three times as likely as males to be sexually abused. Black children are more than 1.5 times as likely to be physically abused, and 5 times more likely than white children to die of physical abuse or neglect. Rates of abuse—physical and sexual—are 6 times higher for children in families with income under $15,000 than for other children. Assaults of family members are more than twice as likely as violence between strangers to occur as part of a chronic pattern. Four commonly suggested causes of family violence are chronic alcohol use, social isolation of the family, depression, and some intergenerational mechanism through which a high potential for

SUMMARY 11 violent behavior is transmitted from parents to children. However, better research is needed to determine whether alcohol use and depression are causes or effects of such behavior, and whether the intergenerational transmission occurs as a direct effect of victimization or through some more complex mechanism that is common to both abuse and neglect. Systematic evaluations of preventive interventions for intrafamily violence have begun to occur. Visiting nurse programs appear to have some potential to reduce the prevalence of child abuse and should be tested further. With respect to police responses to partner assault, randomized experiments have not consistently shown arrest to have a deterrent effect. There is a general lack of systematic evaluations of nonpolice preventive interventions, and there are no comparisons of police with nonpolice preventive interventions in partner assaults. The substantial amount of violence inflicted in domestic situations should encourage the allocation of resources to comparative tests of existing and new interventions that show promise of reducing domestic violence. These include alcohol abuse treatment and anger management training for assaulters, practical assistance and training in shelters to help repeat victims become self-sufficient, and criminal justice interventions such as restraining orders and nonincarcerative sanctions for assaulters. Biological Perspectives on Violent Behavior The psychosocial development of individual potentials for aggressive and violent behavior is potentially influenced by genetics, by neurobiologic characteristics, and by consumption of alcohol and other psychoactive drugs. Genetic Influences Strong evidence from Scandinavian studies points to genetic influences on antisocial personality disorder in adults, a diagnostic category that includes persistent assaultive behavior. Evidence of a genetic influence specific to violent behavior is mixed, however, and neither relationship has been studied in U.S. samples. If genetic predispositions to violence are discovered, they are likely to involve many genes and substantial environmental interaction rather than any simple genetic marker. By themselves, genetic influences cannot explain either short-run temporal fluctuations in violence rates or variation in rates

SUMMARY 12 among countries. Genetic processes may, however, account for individual or family-level deviations from aggregate patterns within a society. Neurobiologic Processes Neurobiologic processes are the complex electrical (neurophysiological) and chemical (neurochemical and neuroendocrine) activities in specific brain regions that underlie all externally observable human behaviors. For at least five reasons, neurobiologic research on violent behavior should be expanded and integrated with research on the psychosocial and macrosocial causes of violence. First, specific neurobiologic “markers" for an elevated violence potential may eventually be discovered, most likely in neurological responses to external stimuli. Second, preventable neurobiologic abnormalities—due to inadequate prenatal care, childhood head injuries, and exposure to neurotoxins such as lead —may increase the risk of school failure and of poor peer and other interpersonal relationships that are empirically linked to subsequent aggressive behavior. Third, knowledge of the neurological activity that underlies violent behavior could assist efforts to develop pharmacological interventions that prevent violent behavior by some individuals, without undesirable side effects. Fourth, the use of psychoactive drugs, especially alcohol, may alter some individuals' neurobiologic functioning in ways that make violent behavior more likely. Fifth, recent improvements in the technology for measuring neurobiologic responses hold out the prospect for adding more precise information with fewer risks and burdens on research subjects. To date, no known neurobiologic patterns are precise and specific enough to be considered reliable markers for violent behavior, whether sexually related or not. However, findings from animal and human studies point to several features of the nervous system as promising sites for discovering such markers and designing preventive therapies. Knowledge of the neurological underpinnings of violent behavior is, quite properly, limited because more precise measurement techniques tend to impose greater burdens and risks on research subjects. Decisions to undertake specific research projects should balance these burdens against the value of the information sought and the likelihood of success. Research using animal subjects is a means of obtaining insights that may apply to violent human behavior without engaging human subjects, especially when the

SUMMARY 13 work is based on multiple species, including nonhuman primates, in both laboratory and seminatural settings. As with human subjects, each animal study should be designed to inflict the least possible stress and harm on subjects without invalidating scientific protocols. Brain Dysfunctions Brain dysfunctions that interfere with language processing or cognition are especially common in conduct-disordered children, early school failures, delinquents, criminals and diagnosed psychopaths— populations with elevated risks of committing violent acts. At least three causes of these dysfunctions are preventable: exposure to lead; head injuries; and expectant mothers' use of alcohol, cocaine, opiates, or tobacco during pregnancy. Although not normally thought of as violence prevention programs, efforts to reduce these risks could have significant long-term payoffs in reducing future violent behaviors. Alcohol, Other Psychoactive Drugs, and Violence Potentials Long-term heavy alcohol use is a predisposing factor for violent behavior at least for adults who showed both chronic aggressive behavior and alcohol abuse in childhood or early adolescence. Adult problem drinkers are more likely to have histories of violent behavior, but alcoholics are not more prevalent among violent offenders than among other offenders. Other psychoactive drugs have different predisposing links to violent behavior depending on the amount and pattern of use. Taking marijuana or opiates in moderate doses temporarily inhibits aggressive and violent behavior; withdrawal from opiate addiction, however, may lead to heightened aggressive and defensive reactions. Chronic use of opiates, amphetamines, marijuana, and PCP increases the risk of violent victimization by altering the nervous system in ways that occasionally disrupt social communications, but it has not been pharmacologically linked to any increased potential for violent behavior. Long- term frequent use of amphetamines, LSD, and PCP has changed a few individuals' neurochemical functioning in ways that induced violent outbursts, but examples are extremely rare except among users with preexisting psychopathology. No evidence has yet established direct neurobiologic links between violent behavior and acute or chronic use of powdered cocaine. However, more research is urgently needed on the pharmacological effects of smoked cocaine or "crack," which enters the brain more directly. While the pharmacological effects of alcohol and other drug use

SUMMARY 14 on violent behavior have been fairly well established, their role in violence also depends on the situational and social context in which they are commonly used. While these relationships are less precisely understood, ethnographic research on alcohol use suggests both that its role in violence depends on drinkers' expectations and on cultural norms—even binge drinking is commonly observed in some non-European cultures without violent aftermaths. For illegal psychoactive drugs, the illegal market itself accounts for far more violence than pharmacological effects. Research also points to occasional violence in the course of obtaining money to buy drugs, and an unknown amount of violence occurs, especially in families, in disputes over expenditures, time spent away from home, and other indirect consequences of drug and alcohol use. SOCIAL PROCESSES AND VIOLENT CRIME Interaction effects are important in understanding how social processes affect violent crime. For example, ethnicity and socioeconomic status (SES) appear to interact: at low SES levels, blacks are more likely to be homicide victims than whites; but at higher SES levels the differential attenuates or disappears. What social factors account for the variation? For at least 50 years, sociologists have pointed to three structural factors—low economic status, ethnic heterogeneity, and residential mobility. Subsequent research has supported these findings and refined them. This work points to: • concentrations of poor families in geographic areas and greater income differences between poor and nonpoor (income inequality); • measures associated with differential social organization such as population turnover, community transition, family disruption, and housing/population density—all of which affect a community's capacity to supervise young males; and • indicators of opportunities associated with violence (e.g., illegal markets in drugs and firearms). In addition, some individual-level risk factors for violent crimes point to possible community-level causes. Ineffective parenting, drug use, school failure, and a poor employment history are all more likely to occur in communities in which illegal markets are nearer at hand than are prenatal and pediatric care, good schools protected from violence, and legitimate employment opportunities. Communities that present different distributions of occasions

SUMMARY 15 for learning violent behaviors can be expected to produce quite different distributions of developmental sequences. There is a critical need to understand how these risk factors interact. For example, there are poor communities with low levels of violence. However, interactions between ethnicity and community characteristics are particularly hard to disentangle empirically because poor minorities are so much more likely than poor whites to be concentrated in communities in which a very high percentage of residents live below the poverty line. Community Characteristics Quantitative indicators of community disorganization include high housing density, high residential mobility, high percentages of single-parent families and the occurrence of neighborhood transitions—both economic decline and gentrification. These appear to account for more of the geographic variation in violent victimization rates than do measures of poverty and income inequality. These indicators appear to reflect a breakdown of social capital—the capacity to transmit positive values to younger generations. This breakdown appears in such intangibles as parents' inability to distinguish neighborhood youth from outsiders, to band together with other parents to solve common problems, to question each others' children, to participate in voluntary organizations and friendship networks, and to watch neighborhood common areas. Single parents who work have less time for such activities and constant family turnover in large multidwelling housing units makes them more difficult to carry out. Many "old heads"—community elders who took responsibility for local youth—have left urban communities, and the status of those who remain is diminished by contrast with the rise of successful young entrepreneurs in illegal markets. Social and Economic Structure and Organization The economic, organizational, and social niches in which poor people tend to live are disadvantaged in ways that defy easy measurement. These include isolation from legitimate economic opportunities and from personal contacts with those who control resources in the larger society. Legitimate routes to social status, income, and power are often severely limited in these communities. Structural economic changes of the last decade have reduced employment opportunities for low-income urban minorities and

SUMMARY 16 increased the numbers of such families living near or below the poverty level. There has been an exodus of economically stable and secure families, which contributes to the decline of institutions of socialization and informal control. Measuring the causal influence of these trends is difficult for many reasons— including the fact that high levels of violence themselves may encourage the most stable families to leave the central cities. Community Culture Ethnographic studies of urban communities, primarily black and Hispanic, provide important hypotheses about how local cultures that support violence develop as a by-product of individuals' and groups' efforts to maintain and increase their social status. First, if success in illegal markets requires violence, then violence levels may increase as illegal markets assume a more central role in the community's economy. Second, violence levels may increase as traditional community elders lose status to successful criminals. Third, as success in illegal markets transforms the symbols of social status to expensive material possessions, potentially violent disputes over those status symbols may increase. Fourth, because disputes in illegal markets cannot be settled through formal mechanisms, an increase in illegal marketing activity may increase levels of dispute resolution through violent means involving firearms, especially while informal "rules of the game" develop. Fifth, when law-abiding members of a community lose faith that public authorities can or will maintain order, many feel compelled to arm themselves for self-protection. The best tests of these hypotheses would involve interventions that reduce the size and centrality of illegal markets in urban economies, that restore or enhance the social status of traditional community leaders, that increase the salience of social status symbols other than material goods attained through criminal activity, and that enhance the ability of public authorities and community-based institutions to cope with community problems and maintain order. The challenges lie in designing and implementing such interventions, in adapting them to the ethnic and cultural diversity of the communities, and in evaluating them. Gangs and Violence Gang diversity makes generalizations about their role in promoting or inhibiting violence difficult. Not all gangs regularly

SUMMARY 17 participate in violence or drug distribution. For those that do, intergang violent behavior serves similar purposes to interpersonal violent behavior: protecting reputation, resources, or territory. Such gangs may reward members who demonstrate prowess in intragang fighting. Gang violence associated with crack markets is widely perceived to have increased during the 1980s. Again, however, the patterns are not uniform. Research in New York, Los Angeles, and Miami found gang members less likely than other hard-core delinquents to be crack dealers. Research is needed to understand more about the roles of gangs in encouraging or mediating violent behaviors among adolescents. THE CIRCUMSTANCES OF VIOLENCE A promising approach to the understanding, prevention, and control of violence—a perspective with roots in both criminology and public health—is to focus on the places where violence occurs. The incidence of violent events varies widely in space—by city, neighborhood, and specific address. The greatest variation is found across locations within cities; for example, although 97.8 percent of all Minneapolis addresses generated zero robbery calls to police in 1986, 8 generated more than 20 calls each. The violence potential of a situation depends on risk factors in both encounters and places. Examples of hazardous encounters in the community include disputes, illegal drug transactions, and robberies. Among the characteristics of encounters that affect the probability of a violent event are the nature of preexisting relationships among the participants, the degree to which communications are impaired by alcohol or other psychoactive drugs, and the proximity of an individual who could intervene. The presence of firearms potentially modifies both the probability and the severity of a violent event. Some violent events arise out of behavioral interactions or exchanges: threats and counterthreats, the exercise of coercive authority, insults and retorts, weapons displays. Violent exchanges and responses to the exercise of authority can accompany encounters between police and citizens, and inmates and custodians in prisons and jails. The dynamics of these exchanges in high-risk encounters are only partially documented, but they can be expected to differ across ethnic and socioeconomic cultures and to depend on the visibility of encounters to public view. Improved understanding of these dynamics could lead to preventive interventions to modify high-risk encounters.

SUMMARY 18 Illegal Markets as High-Risk Settings It is not surprising that illegal markets are high-risk settings for violence. Illegal markets include those for drugs, firearms, and illegal services such as prostitution and loan-sharking. Physical and organizational structures of the markets may influence the degree of violence. A few ethnographic studies suggest that violence in prostitution, for example, is greater in settings over which the seller has less control over others' access. Thus "call-girl" operations are apparently less violent than open-air streetwalking, but more violent than houses of prostitution. Similarly, in drug markets, runner-beeper drug delivery systems may entail less violence than open-air markets, while heavily fortified crack houses may experience still less risk. But the hypotheses remain to be tested. The effects of various enforcement strategies on the level of violence associated with illegal markets need additional study. Firearms and Violent Events Mortality rates from firearm violence are high in the United States compared with other countries and rising, especially among young black males. The nature of the causal relationship between the availability of firearms and mortality rates from firearm violence, especially involving handguns and so-called assault weapons, is a matter of intense public interest and often emotional debate. Available research does not demonstrate that greater gun availability is linked to greater numbers of violent events or injuries. However, what is clear is that gun-inflicted injuries have more lethal consequences than injuries inflicted by other weapons. This suggests that making guns less available in high-risk situations (e.g., in the hands of unsupervised juveniles and others barred from legal gun markets, in homes with histories of family violence, in "fighting bars") might reduce the number of homicides. Educational, technological, and regulatory strategies can be devised with the objectives of changing how handguns are used and stored, changing their allocation from higher-risk to lower-risk segments of the population, reducing their lethality, or reducing their numbers. For any of these policies to reduce homicides, two conditions must be met: the policy must reduce violent uses of at least some types of guns and they must not be replaced with more lethal weapons. Over 80 percent of the firearms used in crimes are reportedly

SUMMARY 19 obtained by theft or through illegal or unregulated transactions. Therefore, while public debates continue over the wisdom of new regulations for firearms, we believe that priority should be placed on evaluating the effects of three strategies for enforcing existing laws governing the purchase, ownership, and use of firearms: • disrupting illegal gun markets using both the centralized and street-level tactics currently in use for disrupting illegal drug markets; • enforcing existing bans on juvenile possession of handguns; and • community-oriented or neighborhood-oriented police work involving close coordination with community residents and community-based organizations to set enforcement priorities and to assist in enforcement and thereby to reduce perceived need for individual gun ownership. A STRATEGY FOR IMPROVING THE UNDERSTANDING AND CONTROL OF VIOLENCE Multiple factors, including those summarized in Table S-1, have been found to correlate with the probability of violent events. The correlations are low by conventional standards, inconsistent across settings, and usually specific to particular types of violent events. The causal mechanisms that underlie the correlations are not well understood. Nonetheless, awareness of these factors does suggest opportunities for understanding and preventing particular types of violent events. The array of potential intervention sites for violent interpersonal events is very broad, ranging from neurobiologic processes to external conditions such as access to lethal weapons and the social structure of nonviolent opportunities for advancement. In considering each site, a systematic problem-solving strategy of innovation—diagnosing specific violence problems and designing preventive interventions, evaluating them, using the results to refine them, and replicating the evaluation—offers the greatest potential of improved understanding and control. Even this approach, which is commonplace in public health and medical science, cannot be expected to rapidly reduce overall violence levels. However, sustained collaborations of this sort by practitioners, evaluators, and basic scientists can be expected to yield significant inroads against specific forms of violence on which they are focused.

SUMMARY 20

SUMMARY 21 RECOMMENDATIONS The panel found that a substantial knowledge base exists regarding some aspects of violent events and behaviors and that certain areas of knowledge are expanding rapidly. However, we were frustrated to realize that it was still not possible to link these fields of knowledge together in a manner that would provide a strong theoretical base on which to build prevention and intervention programs. For that reason, our recommendations primarily concern the research needed to improve our understanding of mechanisms at the individual, group, and community level and evaluations of the interventions that appear most promising. To make progress in the understanding, prevention, and control of violent behavior, we call for a balanced program of efforts with short-term and long-term payoffs: (1) problem-solving initiatives of pragmatic, focused, methodologically sound collaborative efforts by policy makers, evaluation researchers, and basic researchers. (2) modifying and expanding national and local violence measurement systems for diagnosing particular violence problems and measuring the effects of interventions designed to solve them. (3) programs of research projects in areas that have been largely neglected by federal violence research sponsors. (4) the multicommunity research program described in Chapter 3, which is intended to expand society's capacities to understand and to modify community-, individual-, and biological-level processes that influence individuals' potentials for violent behavior. The problem-solving initiatives and research programs in neglected areas can fairly quickly make incremental contributions to the understanding, prevention, and control of violent behavior. The improvement of violence measurement systems and the multicommunity research program, while requiring longer initial investment periods, will lay the groundwork for better diagnosis and understanding of violence in this country and for the design of more effective intervention programs. Problem-Solving Initiatives In the next few years, sustained collaboration by policy makers, disciplinary researchers, and evaluation researchers in these areas could make major cumulative contributions to better understanding of specific violence problems and of interventions that may prevent and control them.

SUMMARY 22 Recommendation 1: We recommend that sustained problem-solving initiatives be undertaken in six specific areas for which systematic intervention design, evaluation, and replication could contribute to the understanding and control of violence: (a) intervening in the biological and psychosocial development of individuals' potentials for violent behavior (Chapter 3), with special attention to preventing brain damage associated with low birthweight and childhood head trauma, cognitive-behavioral techniques for preventing aggressive and violent behavior and inculcating prosocial behavior, and the learning of attitudes that discourage violent sexual behavior; (b) modifying places, routine activities, and situations that promote violence (Chapter 3), with special attention to commercial robberies, high-risk situations for sexual violence, and violent events in prisons and schools; (c) maximizing the violence reduction effects of police interventions in illegal markets (Chapters 4 and 6), using systematic tests and evaluations to discover which disruption tactics for the illegal drug and firearm markets have the greatest violence reduction effects; (d) modifying the roles of commodities—including firearms, alcohol, and other psychoactive drugs—in inhibiting or promoting violent events or their consequences (Chapters 4, 5, and 6), with special attention to reducing weapon lethality through public education and technological strategies; ascertaining patterns of firearms acquisition and use by criminals and juveniles; ascertaining and modifying the pharmacological, developmental, and situational processes through which alcohol promotes violent behavior; pharmacologically managing aggressive behavior during opiate withdrawal; ascertaining whether smoking cocaine promotes violence through special pharmacological effects; and reducing drug market violence by reducing demand for illegal psychoactive drugs; (e) intervening to reduce the potentials for violence in bias crimes, gang activities, and community transitions (Chapter 3); and (f) implementing a comprehensive initiative to reduce partner assault (Chapters 3 and 5), including risk assessment; experimentation with arrest, less expensive criminal justice interventions, public awareness campaigns, batterers' counseling programs, alcohol abuse treatment for perpetrators, and family

SUMMARY 23 services; and further analyses of the relationships between women's shelter availability and assault and homicide rates. Improving Statistical Information Systems Many questions of fundamental policy and scientific importance cannot be answered today, and emerging violence patterns and problems are sometimes slow to be discovered, because of basic limitations of the systems for gathering information on violence. Recommendation 2: The panel recommends that high priority be placed on modifying and expanding relevant statistical information systems to provide the following: (a) counts and descriptions of violent events that are receiving considerable public attention but are poorly counted by existing measurement systems. These include but are not limited to intrafamily violence; personal victimizations in commercial and organizational robberies; violent bias crimes; and violent events in schools, jails, and prisons; (b) more comprehensive recording of sexual violence, including incidents involving intimates, incidents of homicide and wounding in which the sexual component may be masked, and more complete descriptions of recorded events; (c) baseline measurements of conditions and situations that are thought to affect the probability of a violent event (e.g., potentially relevant neurological disorders, arguments between intoxicated husbands and wives, drug transactions, employees handling cash at night in vulnerable locations); (d) information on the treatment of violence victims in emergency departments, hospitals, and long-term care facilities; links to data on precipitating violent events; and development of these data as a major measurement system; (e) information on long- and short-term psychological and financial consequences of violent victimization and links to data on violent events; (f) measurements of violence patterns and trends for small geographic and jurisdictional areas, as baselines for measuring preventive intervention effects; and (g) information system modifications to record more detailed attributes of violent events and their participants, in order to facilitate more precise studies of risk factors for

SUMMARY 24 violence and evaluations of preventive interventions to reduce it. Classification and measurement of sexual violence present special problems. Because violent sexual behaviors are diverse, better classification is essential for advancing its understanding and control. Classifications should be designed to facilitate effective treatment. Moreover, to reverse a long-standing pattern in classification research, special priority should be placed on improved classification of men who commit violent sexual acts against intimates. These men appear to be underrepresented in institutional samples of sex offenders. Research in Neglected Areas Seven research areas have been largely starved of resources for decades while applicable theory, measurement, and methodology have advanced. As a result, substantial and rapid progress can be expected from relatively small-scale research in the neglected areas. Recommendation 3: We call for new research programs specifically concerned with the following areas: (a) nonlaboratory research on the instrumental effects of weapons on the lethality of assaults, robberies, and suicide attempts (Chapter 6); (b) integrated studies of demographic, situational, and spatial risk factors for violent events and violent deaths (Chapter 3); (c) comparative studies of how developmental processes in ethnically and socioeconomically diverse communities alter the probabilities of developmental sequences that promote or inhibit violent behavior (Chapter 3); (d) systematic searches for neurobiologic markers for persons with elevated potentials for violent behavior (Chapter 3); (e) systematic searches for medications that reduce violent behavior without the debilitating side effects of “chemical restraint" (Chapter 3); (f) integrated studies of the macrosocial, psychosocial, and neurobiologic causes of sexual and other violence among strangers, intimate partners, and family members (Chapters 3 and 5); and (g) studies of violent behavior by custodians against wards (Chapter 3).

SUMMARY 25 There is a need now to lay the basic research groundwork for the next generation of preventive interventions. Recommendation 4: The panel calls for a new, multicommunity program of developmental studies of aggressive, violent, and antisocial behaviors, intended to improve both causal understanding and preventive interventions at the biological, individual, and social levels (Chapter 3). This multicommunity study would include initial assessments, follow-ups, and randomized experiments for two cohorts in each community—a birth cohort and a cohort of 8-year-olds. Compared with other programs of longitudinal studies, this one would be distinguished by the combination of: (1) specific emphasis on the relationships between aggressive and violent behavior, including social-level influences on those behaviors; (2) a multicommunity design to facilitate more extensive study of cultural and biosocial influences, both on developmental sequences and on intervention effects; (3) neurobiologic measurements that are as specific for relevant hypothesized processes in the brain as is ethically and technically feasible; (4) designs that facilitate analyses of protective and aggravating conditions and factors in families, peer groups, schools, and communities; (5) randomized tests of interventions that, on the basis of causal understanding at the social, psychological, and biological levels, show promise of fostering the development of prosocial behavior and inhibiting the development of potentials for violent behavior; (6) oversampling of high-risk categories and special efforts to minimize attrition by study subjects in those categories; and (7) cross-validation of official record and self-report versions of violent events. The Level of Research Support In addition to recommending priority areas for research, the panel also finds that research and evaluation funding should be increased if the important opportunities for studying and preventing violence are to be exploited. We surveyed federal agencies

SUMMARY 26 and identified about $20,231,000 in intramural and sponsored violence research in fiscal year 1989. While that amount may sound large, it amounts to only $3.41 per 1988 event of violent victimization, and is only a tiny fraction of the estimated average cost imposed on society by each violent event. FIGURE S-1 Federal support of violence research, fiscal 1989, by agency. As Figure S-1 shows, the Department of Health and Human Services (DHHS) provides the majority of federal violence research support, yet a large number of agencies contribute significant funds. The structure offers support for diverse approaches, but it also creates difficulties. In particular, the fragmentation and segmentation of sponsorship makes it difficult to initiate and maintain projects with a broad, comprehensive orientation to violence. Because most federal support is for two years or less, the problem is especially acute for interdisciplinary projects that require long-term commitments of large annual amounts. The segmentation also creates gaps into which important research topics without visible constituencies can fall. The science policy problem is to modify the existing structure in ways that preserve diversity while increasing interdisciplinary work, the coordination of research funding, and increased support of long-term research projects.

SUMMARY 27 The report discusses options that might be employed to achieve these goals. Regardless of the approach chosen, the panel urges that the following principles apply: broad mandates that encompass basic and applied research; maximum feasible independence from political forces in setting its research agenda; and a commitment to diversity and collaboration across the social, behavioral, and biological sciences, evaluation research, and policy analysis. REFERENCES Bureau of Justice Statistics 1992 Criminal Victimization in the United States, 1990. Washington, D.C.: U.S. Government Printing Office. Federal Bureau of Investigation 1991 Uniform Crime Reports for the United States: 1990. Washington, D.C.: U.S. Government Printing Office.

SUMMARY 28

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Understanding and Preventing Violence: Volume 1 Get This Book
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By conservative estimates, more than 16,000 violent crimes are committed or attempted every day in the United States. Violence involves many factors and spurs many viewpoints, and this diversity impedes our efforts to make the nation safer.

Now a landmark volume from the National Research Council presents the first comprehensive, readable synthesis of America's experience of violence--offering a fresh, interdisciplinary approach to understanding and preventing interpersonal violence and its consequences. Understanding and Preventing Violence provides the most complete, up-to-date responses available to these fundamental questions:

  • How much violence occurs in America?
  • How do different processes--biological, psychosocial, situational, and social--interact to determine violence levels?
  • What preventive strategies are suggested by our current knowledge of violence?
  • What are the most critical research needs?

Understanding and Preventing Violence explores the complexity of violent behavior in our society and puts forth a new framework for analyzing risk factors for violent events. From this framework the authors identify a number of "triggering" events, situational elements, and predisposing factors to violence--as well as many promising approaches to intervention.

Leading authorities explore such diverse but related topics as crime statistics; biological influences on violent behavior; the prison population explosion; developmental and public health perspectives on violence; violence in families; and the relationship between violence and race, ethnicity, poverty, guns, alcohol, and drugs.

Using four case studies, the volume reports on the role of evaluation in violence prevention policy. It also assesses current federal support for violence research and offers specific science policy recommendations.

This breakthrough book will be a key resource for policymakers in criminal and juvenile justice, law enforcement authorities, criminologists, psychologists, sociologists, public health professionals, researchers, faculty, students, and anyone interested in understanding and preventing violence.

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