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Understanding and Assessing Aggression and Violence

Abstract and Keywords

This article examines the issues involved in understanding and, especially, assessing, human aggression and violence. First, it defines aggression and discusses a broad range of factors that influence its assessment, before differentiating individualized from generalized assessments. In the former, the clinician analyzes the factors influencing aggressive behavior in a particular individual. A conceptual framework, the “algebra of aggression,” is offered for analyzing physiological and psychological factors, such as instigation, inhibitions, and habit strength, which influence the relative response strength of different aggressive and non-aggressive acts. Generalized assessments are focused on identifying which members of a group, such as applicants for parole, are most likely to be aggressive. A number of subjective and objective rationally and actuarially derived risk-assessment instruments are described and evaluated.

Keywords: aggression, violence, individual assessments, generalized assessments, risk assessment, algebra of aggression, instigation, inhibitions, habit strength

On August 1, 1966, a “false negative” shot 38 people on the University of Texas's (UT) Austin campus, killing 14. Several weeks earlier, Charles Whitman, a UT student, had gone to the student health center complaining of headaches and uncontrollable urges to shoot people at random from the 22-story tower that dominates the campus. The psychiatrist whom Whitman consulted prescribed an analgesic for the headaches and suggested that he return for another session the following week. Instead, on the night of July 31, Whitman killed his mother and, later that evening, his wife. The following morning, he donned the uniform of a maintenance worker, packed a trunk full of guns and ammunition, and wheeled it to a tower elevator. Ascending to the top floor, he shot and killed the attendant, sealed off the elevators, and took his weapons to the balustrade overlooking the campus. When he thought classes were about to change, flooding the campus with students, he opened fire. Along with hundreds of others UT faculty and students, I was pinned down for over 90 minutes until a police officer and an armed civilian ascended the tower stairs and fatally shot Whitman.

When assessing the risk of aggression and violence, it is the possibility of missing false negatives, such as Whitman, that most worries clinicians. However, it is the false positives, namely individuals incorrectly diagnosed as being aggressive, who are far more numerous (Otto, 1992; Wollert, 2006).

The consequences of being labeled dangerous can be severe. They can include prolonged imprisonment, revocation of probation or parole, involuntary commitment to a mental health facility, and loss of parental rights in custody disputes. In Texas, people convicted of capital crimes who are assessed as being a continuing threat to society often end up on death row (Cunningham & Reidy, 1999; Dorland & Krauss, 2005; Edens, Buffington-Vollum, Keilen, Roskamp, & Anthony, 2005). In many states, sex offenders regarded as dangerous may be civilly committed, subjected to preventive detention, or effectively barred from living in some communities (Alexander, 2004; Mercado & Ogloff, 2007).

(p. 543) Defining Aggression and Violence

Johnson 1972, p. 8) wrote that, “the most important thing that can be said about defining aggression” is that, “there is no single kind of behavior that can be called ‘aggressive’ nor is there any single process which represents ‘aggression’.” Indeed, it would be possible, although not very helpful, to devote this entire chapter to a discussion of the difficulties encountered in formulating a universally acceptable definition of aggression (Baron, 1977; Johnson, 1972; Megargee, 1993).

Several important issues must be considered when one tries to define aggression or violence. The first is “intentionality.” I am sure everyone agrees that Charles Whitman's deliberately planned and well-executed mass murder constituted aggression and violence. However, was it also aggression or violence in February 2006 when Vice President Cheney accidentally sprayed a hunting partner with birdshot? Some behaviorists attempted to avoid this issue by defining aggression as any behavior that, “delivers noxious stimulation to another organism” regardless of whether or not it was intended (Buss, 1961, p. 1). However, today most authorities insist that the perpetrator must intend to harm the target for the behavior to be considered aggressive (Anderson & Bushman, 2002).

Assuming intent is a necessary component of aggression, the next question is whether harmful intent alone is sufficient to constitute aggression. If a woman who plans to commit a suicide bombing in a crowded market is arrested before she can carry out her attack, is her scheme alone enough to be considered aggression?

“Legality” is yet another issue. Charles Whitman and the two men who shot him to death all committed homicide on that hot August afternoon. Were all three engaging in violent aggression? Some authorities reserve the terms “aggression” or “violence” for illegal or criminal behavior while others include any act that harms another human being, regardless of its legality.

The “target” of the aggressive behavior is another concern. Anderson and Bushman (2002, p. 28) regard human aggression as harmful “behavior directed toward another individual,” but what of harm inflicted on other targets such as animals, objects, or property? Is someone who deliberately sets a forest fire aggressive if no people are injured? What about a worker who slaughters animals at a meatpacking plant? In my seminars on aggression, discussions of these issues could go on for hours, even days, if left unchecked.

In this chapter, which is limited to human behavior, “aggression” refers to overt verbal or physical behavior that can harm people and other living creatures by causing them distress, damage, pain, or injury, or by damaging their property or reputation. “Violence” is severe physical aggression that is likely to cause serious damage or injury. To be considered aggression, the harm must be intended or the possibility of such harm accepted by the perpetrator. Such behavior will be viewed as aggressive whether or not hurting the victim was the aggressor's primary intention and regardless of whether the behavior is classified as legal or illegal in the particular society in which it occurs.

This definition includes instrumental aggression where the primary intent is not necessarily to harm someone but in which a person's pain or suffering is an acceptable outcome, as well as the legal aggression or violence that might occur in military combat. It does not include accidental or unintentionally harmful behavior, or unavoidable pain inflicted for altruistic reasons such as might occur in medical or dental treatment.1

Heterogeneity of Aggression and Violence

Just as there is no simple definition of aggression, there is also no single prototype for those who behave aggressively or who engage in violence. After Seung-Hui Cho shot and killed 32 people on the Virginia Tech campus in April 2007, I was asked how closely he resembled Charles Whitman, whom I had studied four decades earlier. The two could hardly have been more different. Whitman, a former altar boy and Eagle Scout, was a hard-working, wellregarded, achievement-oriented married veteran with a temporal lobe tumor. Cho was an estranged, alienated, underachieving misfit with no known physical impairment whose agitated behavior and bizarre writings frightened his teachers and fellow students.

In the 1960s, many social psychologists thought that, although the causes of the milder forms of aggressive behavior that they studied in the laboratory could be quite complex, violent crimes were typically committed by offenders who had inadequate controls and inhibitions against aggressive acting out (Berkowitz, 1962; Buss, 1961). Such undercontrol could result from (a) a failure to incorporate society's moral codes and prohibitions against aggression, (b) being socialized into a subculture of violence in which aggression or violence was expected and rewarded in certain circumstances, or (c) impairment of normal inhibitions against (p. 544) aggression by organic conditions, toxic substances, or functional psychopathology.

Although many aggressive and violent people clearly do lack adequate inhibitions or controls, we discovered that some extremely violent offenders are, paradoxically, overcontrolled individuals whose rigid and excessive inhibitions against any type of aggressive behavior allow aggressive instigation to accumulate until it is unleashed in one often cataclysmic act, after which they revert to their typical overcontrolled pattern (Megargee, 1966, 1982). In addition to these under-and overcontrolled assaultive types, it is also possible for normally socialized people with culturally appropriate values systems to engage in violence. This includes law enforcement officers and military personnel whose jobs may require them to behave aggressively. Normally socialized people may also engage in aggression in response to being attacked, severely provoked, extremely frustrated, or if they are caught up in the contagious chaos of a riot or rebellion (Berkowitz, 1970).

This heterogeneity makes it unlikely that any single global device for the assessment or prediction of aggression or violence will be universally effective. For example, Hare's Psychopathy Checklist-Revised (PCL-R; Hare, 2003) might be very useful in detecting poorly socialized criminal offenders who have inadequate inhibitions against aggressive behavior or violence, but it is unlikely to identify the normally socialized people driven to aggression by extreme situational factors.

Issues and Factors Influencing Assessments of Aggression and Violence

In addition to the complexity of aggressive behavior, there are a number of other issues that influence its assessment. They include the type of appraisal required, the context and setting in which the assessment takes place, and whether an individual or a group is being assessed.

Type of Appraisal

Most assessments of aggressive behavior fall into one of two general categories: “retrospective” or “diagnostic” assessments in which individuals who have already been violent are evaluated, and “prospective” or “prognostic” assessments in which their potential for future aggression or violence is estimated.

In retrospective assessments, psychologists are typically confronted with aggression that has already occurred and are asked to explain it. Criminal liability might depend on the mental status of the perpetrator at the time of offense. For example, Mary Winkler, a minister's wife who shot and killed her sleeping husband in March 2006, was convicted of a reduced charge of voluntary manslaughter and sentenced to only 210 days of confinement after a psychologist for the defense testified that her husband's abusiveness resulted in a mental disorder that made it impossible for her to form criminal intent (Grinberg, 2007). Retrospective evaluations are especially important in program planning. For example, the management and treatment needs of undercontrolled and overcontrolled assaultive offenders obviously differ greatly (Megargee, 1966).

In prospective or prognostic evaluations or “risk assessments,” psychologists are asked whether a person, group, or even a nation is likely to commit aggression in the future. If so, what form is the aggressive behavior likely to take? Against whom or what is the aggressive behavior likely to be directed? Under what conditions is such aggression most likely to occur? What circumstances or interventions are likely to increase or decrease the risk of such behavior (Borum, Fein, Vossekuil, & Berglund, 1999; Heilbrun & Heilbrun, 1995)? The answers to these questions might be used to help determine whether patients or prisoners are ready for release or if a child should be returned to the custody of a possibly abusive parent. As anyone who has ever bet on a sporting event knows, it is much more difficult to predict what will happen in the future than it is to explain what has happened in the past.

Some assessment techniques work much better in retrospective than in prospective assessments. Retrospectively, the overcontrolled hostility (O-H) scale for the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Megargee, Cook, & Mendelsohn, 1967) can help identify overcontrolled assaultive offenders, but prospectively the O-H scale is of limited utility in predicting violent behavior because of the rarity of this syndrome.

Context and Setting

The context of the assessment and the setting in which it is carried out are also important considerations. Assessments of aggression and violence may take place in jails, prisons, or closed psychiatric wards. Security considerations may dictate that the client is in a cell or even in some sort of restraints, and other people, such as attorneys, correctional officers, or psychiatric aides, may be present. The (p. 545) impact of these factors on the subject's performance need to be considered in such appraisals.

Psychologists who are doing appraisals for third parties, such as pre-sentence evaluations or custody assessments for the courts, may be viewed as adversaries by those being assessed. Professional ethics require that, before they participate in an evaluation, subjects should be told for whom the clinician is working and informed of any limitations on confidentiality (American Association for Correctional Psychology, Standards Committee, 2000; American Psychological Association, 2002; Megargee, 2003, 2006a; Monahan, 1972; Pope, Butcher, & Seelen, 2006).

Criminal offenders and others whose aggressive or violent propensities are being assessed often have a strong stake in the outcome of the evaluation. They may be highly motivated to manipulate the results so that they appear sick or well, incompetent or competent. The assessor must be alert to the subjects' possible efforts to dissimulate or malinger and interpret the findings accordingly (see Chapter 32).

Individualized Versus Generalized Assessments

It is also important to distinguish between “individualized” and “generalized” evaluations. In individualized or “idiographic” risk assessments, the task is to evaluate a particular person. This may involve a retrospective evaluation of someone like Mary Winkler who has already committed an aggressive act, or a prognostic assessment to determine if someone is likely to pose a threat in the future. Sometimes this involves a “targeted” risk assessment, that is, estimating the likelihood that a person will aggress against a specific target, such as a spouse, coworker, schoolmate, or public figure (Borum et al., 1999). In addition to a personality evaluation, targeted risk assessment may require us to assess the potential perpetrator's ability to formulate and carry out a plan of attack, and to assess his or her technical skills, access to weapons, and ability to gain access to the would-be victim (Cohen & Felson, 1979).

In individualized assessments, we typically have access to a much broader array of more detailed information than we do in generalized evaluations. This often includes a detailed case history, psychological testing, and the opportunity to interview the subject as well as others who are familiar with the subject's behavior and attitudes. It is much easier for clinicians to obtain information about situational factors in individualized than in generalized assessments. Interviews conducted in the subject's home are especially valuable because they enable us to evaluate an individual's environment as well as his or her personality.

Generalized or “nomothetic” assessments typically take place in the context of risk prediction. Here our task is to identify which members of a group or class of people are most likely to be involved in aggression or violence. Such generalized assessments often take place in mental health facilities or correctional institutions as a guide to management planning or release decisions. For example, in a federal prison for youthful offenders, Bohn (1979) used our MMPI-based offender classification system (Megargee, Bohn, Meyer, & Sink, 1979; Megargee, Carbonell, Bohn & Sliger, 2001) to identify those prisoners who were (a) most likely to prey on others and (b) most likely to be victimized. By assigning these groups to separate living quarters, the rate of serious assaults was reduced 46%.

In generalized risk assessments, clinicians typically have to rely on a more limited array of data than they have available in individualized appraisals. They may have no personal contact with those being assessed, relying instead on demographic or file-based information or test scores. Information about environmental and situational factors that may facilitate or impede aggressive behavior is often lacking.

Individualized appraisals should enable clinicians to formulate contingent evaluations, specifying the conditions and circumstances under which the person being evaluated is more or less likely to engage in various types of aggressive behavior directed toward certain targets. Generalized assessments are more likely to result in probability statements specifying the likelihood that individuals belong in mutually exclusive “aggressive” or “nonaggressive” groups.

In the sections that follow, I will separately discuss strategies for individualized and generalized assessments of aggression and violence. I will first present a conceptual framework designed to guide individual appraisals. Dubbed the “algebra of aggression” by the U.S. Secret Service agents to whom I taught the system in the 1980s, it considers the various factors that interact to cause someone to choose an aggressive response. I will then describe approaches to nomothetic predictions of aggression, concentrating on the many objective instruments that have been devised in forensic and correctional settings in the last 15 years.

(p. 546) Individualized Assessment of Aggression

The Algebra of Aggression: A Conceptual Framework for the Analysis of Aggressive Behavior

In his recent Sutherland Award address, Nagin (2007) proposed that the concepts of choice and decision making should occupy “center stage” in criminological theory and research. Choices are central to my conceptual framework for understanding human aggression. According to this formulation, every act of human aggression results from the interaction of numerous factors and involves dozens of implicit and explicit choices. This is true whether the act is planned and deliberate or spontaneous and implusive. These choices involve emotions as well as cognitions, physiology as well as psychology, and situational as well as personal factors.

Although we may not be consciously aware of it, at any given time we are confronted with dozens of alternative behaviors; some of which may be aggressive. These potential aggressive responses may be verbal or physical, mild or extreme, direct or indirect. How do we make these choices? According to the algebra of aggression, we typically select the response that appears to offer us the most satisfactions and the fewest dissatisfactions in that particular situation.

This simple statement conceals a rapid but complex internal bargaining process in which we weigh the capacity of each response to fulfill various competing drives and motives against the discomforts or disappointments we might suffer from choosing that response. By means of this “internal algebra,” we calculate the net strength of each possible response, compare it with all the other responses, and select the strongest.

What determines the net strength of a potential response? We must consider both “personal” and “situational” factors. In the case of an aggressive or violent act, we can isolate three personal factors that interact to determine its response strength. The first two induce us to act aggressively while the third deters us from aggressive behavior.

The first personal factor which promotes aggression is “instigation to aggression.” Instigation to aggression is the sum of all the forces that can motivate us to commit a violent or aggressive act. It includes both “intrinsic or angry” instigation, which is our conscious or unconscious desire to harm the victim in some fashion, and “extrinsic or instrumental” instigation, which is our wish for other desirable outcomes that the aggressive act in question might achieve for us, such as economic gain in the case of a robbery or political benefits from an act of terrorism.

The second personal factor contributing to aggressive behavior is “habit strength,” the extent to which a given response has been rewarded or punished in the past. Other things being equal (which they rarely are), the more often we have been reinforced for aggressive behavior in the past, or the more we have observed others being rewarded for aggression, the more likely we are to aggress in the future.

Instigation to aggression and habit strength both induce us to act aggressively. What deters us? Opposing the motivational factors is the third set of personal variables, namely “inhibitions against aggression.” Inhibitions include all the reasons we might refrain from a given aggressive act directed at a particular target. They include both moral prohibitions, which cause us to feel that this act of aggression is wrong, and practical considerations, such as our fear of retaliation. Inhibitions can be general or specific and can vary as a function of the act, the target, and the circumstances.

Instigation, habit strength, and inhibitions are all personal characteristics, but behavior results from individuals interacting with their milieus. The next set of variables is comprised of “situational factors” which encompass all those external factors that may influence the likelihood that we will engage in aggressive behavior. These include “environments,” “settings,” “situations,” and “stimuli,” and they may either facilitate or impede aggressive behavior.

“Reaction potential,” my last major construct, consists of the net strength of any given response after all the inhibitory factors, both personal and situational, have been balanced against the excitatory ones. A response will be blocked and cannot occur whenever the inhibitions exceed the instigation. A response is “possible” (i.e., has a positive reaction potential) if the forces favoring the aggressive response exceed those opposing it. After all the possible responses compete with one another, the one with the highest reaction potential—that is, the capacity to satisfy the most needs at the least cost—should be chosen (Megargee, 1993).

Given this overall conceptual framework, we can then ask salient questions such as, “What are the causes of anger? What happens to instigation once it is aroused? What factors increase or decrease our inhibitions? How might environmental factors be manipulated to increase or decrease the likelihood of aggressive behavior?” General questions such as these can guide psychological research on aggression. (p. 547) When appplied to individual clients in clinical settings, these issues can help us understand our clients' individual dynamics of aggression and suggest interventions that may be useful dealing with their aggressive behaviors.

Given this brief overview of the conceptual framework, let us examine how we can use it in assessment and treatment. We will begin with the personal factors promoting aggressive behavior, intrinsic and extrinsic instigation to aggression and habit strength, inquiring how each of these constructs develop, and how they can be diminished. Next, we will discuss the personal factors deterring aggression, namely inhibitions. After discussing these internal or personal factors, we will move on to the external or situational factors that may facilitate or suppress aggressive behavior and violence.

Intrinsic Instigation to Aggression

Intrinsic instigation to aggression is the conscious or unconscious desire to injure or harm the target in some fashion. Depending on its duration and intensity, we refer to these motives as “anger,” “hostility,” “rage,” or “hatred.” It is important for both assessment and treatment to understand the role of instigation in aggressive behavior.

Sources of Intrinsic Instigation

The first question is the origins of an individual's anger. An understanding of the determinants, both physiological and psychological, can assist in both retrospective and prospective assessment as well as in the management of aggressive behavior patterns.

Physiological sources of instigation include (a) genetic predispositions including temperament and gender; (b) diseases or disorders of the central nervous system such as Whitman's' brain tumor; (c) the influence of hormones including thyroxin, testosterone, and adrenaline; (d) physical illnesses such as encephalitis as well as their associated pain and discomfort; (e) drugs such as phencyclidine (PCP) and steroids as well as toxic factors such as lead paints and pollutants; (f) fatigue, stress and pain; and (g) generalized autonomic arousal. (See Megargee, 1993, pp. 621–624, for a detailed discussion of physiological sources of intrinsic instigation.)

There are also numerous psychological sources of instigation, including (a) frustration (Dollard, Doob, Miller, Mowrer, & Sears, 1939); (b) aversive events and provocations (Berkowitz, 1989, 1990, 2003); (c) physicalor verbal attacks (Azrin, Hake, & Hutchinson, 1965); and (d) territorial intrusions (Ardrey, 1966). Frustration was one of the earliest causes of anger to be studied (Dollard et al., 1939). Researchers learned that the number of frustrations, the strength of the frustrated drive, and the arbitrariness of the frustration all increased the amount of instigation, and that the instigation from several sources could summate (Berkowitz, 1962, 1989). The phenomenon of “road rage” (Novaco, 1991) is a good example of frustration-induced angry aggression.

Over the years, the concept of frustration expanded from the simple blocking of an ongoing goal response postulated by Dollard and his associates (1939) to include interference with learned attitudes and cognitive expectancies about how people should behave and how we should be treated. When these expectations are frustrated, instigation to aggression can result.

In the wake of mass shootings in high schools in the United States and elsewhere, there has been an increased appreciation of the role that ostracism and bullying play in creating instigation to aggression and violence (Jimerson & Furlong, 2006; Vossekuil, Fein, Reddy, Borum & Modzeleski, 2002).

Some societies and religions teach their members to be angry when they witness behaviors that they regard as disrespectful, as evidenced by the widespread Islamic protests over the publication of cartoons depicting the prophet Mohammed in the Danish newspaper Jyllands-Posten on September 30, 2005. Indeed, some honor codes require lethal retribution for perceived affronts, not only of perceived enemies such as Salman Rushdie, but even of relatives who might have disgraced the family or tribe (Anderson & Bushman, 2002; Baumeister, Smart, & Boden, 1996; Berkowitz, 1990, 2003; Cohen, Nisbett, Bowdle, & Schwarz, 1996, Tawfeeq & Todd, 2007).

Reducing Intrinsic Instigation

How people deal with anger or hostility is another important consideration. According to “catharsis” theory, intrinsic instigation should be depleted by attacking the source of the provocation. If this is impossible, angry individuals may reduce instigation by attacking someone else (displacement), choosing an alternative response (response substitution), or observing someone else's aggressive behavior, either in real life or the media (vicarious aggression) (Berkowitz, 1962; Buss, 1961). Hokanson (1970), however, has shown that the instigation-reducing effects of counter-aggression (p. 548) appear to depend on previous learning and cultural values.

Assessing and Treating Intrinsic Instigation

Obviously, the more intense and long-lasting the instigation, the easier it is to assess. Because anger and rage are transitory, we may not observe them in a single session. As with the assessment of other emotions, the more often we interact with a subject, the greater the range of emotions, including anger, we are likely to observe.

Our primary assessment questions are the amount, the duration, and the direction of instigation to aggression: “Is the subject angry?” “How angry?” “How long does he stay angry?” “At whom is she angry?” The secondary questions are what causes this instigation and how does the subject deal with it: “What angers him?” “What does she do when she is angry?”

One of the best ways to assess anger and hostility is also the simplest: asking subjects, using a variety of synonyms, what makes them angry or annoyed, who aggravates them, what they would like to do when they are provoked, to whom they would like to do it, and what it is they actually do and why. Anger is a strong emotion; given the opportunity, many people will express it quite openly, even when it is not in their best interests to do so. Because anger and hostility are difficult to conceal, their friends and associates should also be able to comment on a client's temper.

A number of self-report tests and scales have been constructed to assess anger and hostility. The Buss— Durkee Hostility Guilt Inventory (Buss & Durkee, 1957) features seven scales designed to assess various aspects of hostility and aggression, plus one for assessing guilt over its expression, a potential measure of inhibitions. Spielberger's (1996) State Trait Anger Expression Inventory (STAXI) has three standard scales, “Anger out” (Ax/out), “Anger in” (Ax/in), and “Anger control” (Ax/con), as well as two experimental subscales, “Anger control in” (Ax/con-in) and “Anger control out” (Ax/con-out). Novaco and his colleagues have devised several measures related to anger and its causes, including the Novaco Anger Scale (NAS; Novaco, 1994, 2003), the Novaco Provocation Inventory (NPI; Novaco, 1975, 1988), and the Dimensions of Anger Reaction Scale (DAS and DAS-5; Hawthorne, Mouthaan, Forbes, & Novaco, 2006).

Scales designed to assess anger and hostility are also included on self-report inventories such as the MMPI-2 (Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989). Since instigation to aggression has been implicated as a factor in cardiovascular and gastrointestinal disorders, a number of measures of anger and hostility have been devised for use in behavioral medicine (Chesney & Rosenman, 1985). Most of these scales have obvious content and can easily be dissembled.

Researchers have also devised observational rating instruments such as the Ward Anger Rating Scale (WARS; Novaco, 1994; Novaco & Taylor, 2004) designed to allow staff members to record and quantify inpatients' angry and aggressive behavior over the course of a week.

Ascertaining the sources of instigation to aggression can have important clinical implications for assessment and for treatment. The court that sentenced Mary Winkler to the time she had already served in jail plus some additional counseling probably concluded that she was unlikely to engage in further violence since, by killing her abusive husband, she had already eliminated her major source of instigation to aggression.

With regard to treatment, a clinician might investigate whether a client's frustration and resulting anger stems from unreasonable expectations. If so, cognitive therapy designed to correct these beliefs might be effective (Feindler & Ecton, 1986; Goldstein & Keller, 1987). On the other hand, if the grievance is genuine and the anger justified, a better solution might be to help the client find a more constructive way of coping with the frustrating situation, such as seeking redress in the courts. Cognitive redefinition, especially through humor, is another effective mechanism for reducing instigation (Megargee, 1993).

Extrinsic (Instrumental) Instigation to Aggression

People aggress not only because they want to hurt the victim, but also because they hope aggression may help them attain other goals. As Al Capone reportedly said, “You can get much farther with a kind word and a gun than you can with a kind word alone” (Peter, 1977, p. 141).

Sources of Extrinsic Instigation

There is a vast array of possible extrinsic motives, both primary and secondary. Primary motives include (a) personal gains and satisfactions, such as acquisition of property or enhancement of self-esteem; (b) removal of problems or impediments, such eliminating enemies or witnesses to crimes; (c) achieving social goals, such (p. 549) as power or respect from others; and (d) the attainment of political or religious goals, as exemplified by the conflicts in the Middle East and elsewhere (Megargee, 1982, 1993). And, of course, aggression is part of the job description for many people, including professional athletes, police officers, and military personnel. (See Megargee, 1982, for a detailed discussion of extrinsic motives.)

We need to be alert to secondary as well as primary motives. Although he had robbed banks mainly for the money, a reformed robber told me that he had also enjoyed the adrenaline rush he had experienced playing “cops and robbers” with real guns and cars. Although we psychologists often focus on intrinsic motives such as anger and hostility when working with aggressive people, extrinsic motivation probably leads to as much if not more aggression, especially when we consider large-scale conflicts between groups and nations.

Reducing Extrinsic Instigation

The best way to reduce extrinsic instigation is to eliminate the payoff for the aggressive behavior. If aggression is ineffective in achieving the extrinsic goals, other strategies are more likely to be adopted during the response competition. This is the basic principle underlying the imposition of severe criminal sanctions for violent crimes. Unfortunately, in our society, as well as in many others, it is difficult if not impossible to eliminate all the rewards for aggression.

Assessing and Treating Extrinsic Instigation

Not being a personality trait, extrinsic motivation is much more difficult to assess than intrinsic. Lacking tests to assess instrumental motivation, we must often rely on self-reports elicited in response to probing questions in an interview. We can also infer how aggressive behavior is reinforced from case history data. Obviously, this works better in retrospective than prospective assessments.

The first step in dealing with instrumental aggression is to analyze the contingencies in the client's milieu. What are the payoffs for behaving aggressively? Many cultures and families reward and model aggression (Bandura, 1973; Bandura & Walters, 1963). Moreover, extrinsic instigation can generalize from one situation to another. Parents who berate the umpire at Little League games should not be surprised when their children emulate them and disrespect other adults.

Once we have determined the contingencies reinforcing the undesired aggressive behavior, we should attempt to reduce the reinforcements for that behavior as much as possible. At the same time, we should create nonaggressive opportunities for clients to attain their legitimate goals. While this does not eliminate the aggressive responses from their repertoires, it should make the nonaggressive alternatives more likely to be selected in the response competition.

The effectiveness of this two-pronged approach was demonstrated in an experiment with nursery school children who were misbehaving in order to obtain attention. Brown and Elliott (1965) reduced the students' verbal and physical aggressive behavior by having their teachers systematically reinforce prosocial responses that were incompatible with aggression while minimizing the attention they paid to aggressive responses.

Habit Strength

Reinforcement of aggressive responses increases their habit strength, the last personal factor leading to aggression. Angry aggression is reinforced by the pain or discomfort inflicted on the victim, instrumental by attaining extrinsic goals through aggressive behavior. The stronger the habit strength for a particular aggressive response, the more likely that act and similar behaviors will be selected in the future.

Sources of Habit Strength

Direct reinforcement of our own aggression is the most effective way to increase habit strength. The rewards are strongest for the actual response and generalize to others that are similar to it. A schoolchild motivated to punch an obnoxious playmate in the nose receives stronger reinforcement for doing so successfully than he does for calling his opponent names or telling tales about him to the teacher. If, however, the nose-punching response is blocked, he should obtain some satisfaction from the other lesser responses. Displacement may also take place. If he is unable or unwilling to attack his antagonist, perhaps because the other lad is bigger or is accompanied by his friends, he may take out his anger on another boy who is smaller or weaker.

The more a family, reference group, or culture approves of aggressive behavior, the more secondary reinforcement a person will receive. The boy who punches his obnoxious opponent in the nose is likely to get additional reinforcement from his peers (and, perhaps, not entirely unwelcome attention from his teacher). Girls, who are less likely to be reinforced for physical aggression, are less likely to develop as much aggressive habit strength as boys.

(p. 550) Although direct reinforcement of our own aggressive responses is most effective, we can also develop habit strength indirectly by observing role models successfully engage in aggressive behavior. Children can learn aggressive scripts from observing domestic violence, from watching countless portrayals of aggressive behavior in the media, and from playing violent video games. These aggressive scripts, once learned, can then serve as guides for future aggressive behavior in real-life situations (Anderson & Bushman, 2002; Bandura, 1973; Huesmann, 1986, 1998; Huesmann & Eron, 1986). For example, in the videos Seung-Hui Cho mailed to NBC the day of his multiple killings at Virginia Tech, he acknowledged the influence of Dylan Klebold and Eric Harris's killing spree at Columbine High School in 1999, referring to them as “martyrs” (Healy, 2007).

Reducing Habit Strength

Once acquired, aggressive habits and scripts are extraordinarily difficult to eliminate. As we all learned in Psychology 101, extinction is the only certain technique for eliminating habits. However, extinction requires the elimination of any reinforcement for aggressive behavior, which is virtually impossible in our culture. Although punishment may temporarily suppress aggressive behavior, it does not eliminate aggressive responses from our repertoires. Moreover, to the extent that punishment is frustrating or perceived as an attack, it can also increase intrinsic instigation. This is one reason prisons are often ineffective.

Assessing and Treating Habit Strength

Of all the constructs in the algebra of aggression, habit strength should be the easiest to assess, based as it is on the individual's reinforcement history as documented in the case history. Habit strength is the variable that most strongly predicts aggression; the longer and stronger the history of aggression, the more likely an individual will behave similarly in the future. One can infer strong habit strength from a long history of aggressive behavior, especially if the aggression appears to have been successful. A history of aggressive behavior is a key element in diagnosing Megargee's (1966) undercontrolled assaultive type, and is central to the objective prediction devices used in many mental health and correctional risk assessments (Borum, 1996; Otto, 2000). However, as in the case of the overcontrolled assaultive type, the fact that some people have no known history of aggression or violence is no guarantee that they will never aggress in the future.

With regard to treatment, Brown and Elliott's (1965) experiment also demonstrated how difficult it is to eliminate habits once they have been formed. As we noted, both verbal and physical aggression diminished during their experiment when their nursery school teachers were instructed to minimize the amount of attention they paid to aggressive students. Unfortunately, fighting resumed once the experiment was over, presumably because the teachers could not bring themselves to continue ignoring physical aggression while rewarding only prosocial behavior.

Inhibitions Against Aggression

Opposing instigation and habit strength are inhibitions against aggression. Inhibitions include both moral prohibitions and pragmatic concerns. They can be general or specific, lasting or temporary, and they vary as a function of the aggressive act, the target, and the circumstances.

Sources of Inhibitions

Moral prohibitions go by various terms such as “taboos,” “conscientiousness,” and “superego.” In the course of normal development, we all learn that certain aggressive acts directed at particular people are morally wrong. For example, in most societies aggression against one's parents, especially one's mother, is considered wrong, while attacking an enemy, especially one who is from an alien culture, is more acceptable.

Pragmatic issues are another source of internal inhibitions. One practical concern is the fear that bad things, such as punishment or retribution, may occur following a particular aggressive act. Fearing he might be attacked by a mob following his planned assassination of President James A. Garfield in 1881, Charles Guiteau hired a cab to wait and take him to the DC prison as soon as he had shot the president (Clark, 1982).

Another concern is the fear that the proposed act might fail to accomplish its objective. On several occasions in 1972, Arthur Bremer set out to assassinate President Richard Nixon, but was deterred when he was unable to get close enough to get a clear shot at the President. In a classic case of displacement, he next targeted and eventually shot Gov. George Wallace, who was running for the Democratic nomination for president (Clark, 1982).

Reducing Inihibitions

Unfortunately, it is much easier to decrease inhibitions than it is to foster them. Physiological factors that reduce inhibitions include (a) injuries or (p. 551) diseases affecting the central nervous system; (b) certain endocrinological disorders; and (c) the chemical actions of disinhibiting substances such as alcohol.

Among the many psychological causes of inadequate inhibitions against aggression are (a) the failure to develop adequate inhibitions because of deficient socialization or abuse during childhood; (b) growing up in a society that approves of certain acts of aggression or violence; (c) being exposed to social influences, including the media, that model aggressive behavior; (d) conflicting values (i.e., it is wrong to attack someone but right to defend your honor); (e) rationalizations (i.e., aggression is wrong but this is anticipatory self-defense rather than aggression); (f) peer pressure; and (g) contagion. (See Megargee, 1997, for a detailed discussion of inhibitions.) A full assessment of inhibitions must explore whether people's inhibitions against aggression are easily overcome.

Assessing Inhibitions

It is much more difficult to measure inhibitions against aggression than it is to assess instigation to aggression or habit strength (Megargee, 1997). The mere absence of a history of aggressive behavior or failure to express animosity toward others does not necessarily indicate that people have strong inhibitions. A more parsimonious explanation would be that they simply lacked instigation.

To assess inhibitions directly, one must look for circumstances in which people should be motivated to aggress but fail to do so. While such situations can be created in the laboratory, they are difficult to contrive in the clinic. Role playing, group therapy, and direct confrontations in an interview may afford opportunities to observe inhibitions. More often, we have to ask people about what aggressive behaviors they find acceptable or unacceptable under various circumstances. Inhibitions are easier than anger to dissimulate, and potentially self-serving reports need to be cross-checked with the case history and reports by people who have had an opportunity to observe a client's behavior in provocative circumstances.

Often we must rely on indirect evidence. One source of indirect evidence is whether the familial and social history is conducive to the development of well-socialized values. Is a person cautious or impulsive? This involves consideration of stakes as well as risks. The more people have to lose through aggressive behavior, the less likely they are to risk it (Gottfredson, 1987). This is one reason so-called “white collar criminals” are more likely to rob you with a fountain pen than with a pistol, to paraphrase Woody Guthrie's “Ballad of Pretty Boy Floyd.”

Personality tests are another indirect source of data on inhibitions. While there are no adequate tests of inhibitions against aggression per se, there are measures designed to measure overall conscientiousness and socialization. Although Hartshorne and May's (1928, 1929) classic studies demonstrated the specificity of moral prohibitions, other things being equal well-socialized people with strong values are more likely to have inhibitions against those forms of aggression that are censured by their culture than those who are poorly socialized.

Hogan and Ones (1997) describe several personality tests designed to assess “conscientiousness” as one of the so-called basic or “Big Five” personality traits. Chief among them is the NEO PI (Costa & McRae, 1992). The California Psychological Inventory (CPI; Gough & Bradley, 1996) has three scales relevant to inhibitions: Socialization (So), Responsibility (Re), and Self Control (Sc). These scales, which have been validated in many cultures, assess the degree to which individuals have assimilated (So) and understand (Re) their cultural values, and also measure their ability to control their behavior and abide by these precepts (Sc) (Megargee, 1972). Although I use the CPI in nonclinical populations, I prefer to use the MMPI-2 with more deviant or pathological groups. A clinically elevated O-H scale score suggests a conflict between expression or suppression of hostility, but low scores are meaningless (Megargee et al., 1967). Elevations and high points on basic Scales 4, 6, 8, and 9; on supplementary scale MAC-R; and on content scale ASP suggest deficient inhibitions and controls.

No one is more lacking in inhibitions than the psychopath, and Hare's (2003) PCL-R has been related to violent criminal behavior in a number of studies. The PCL-R will be discussed in the section on risk assessment.

Situational Factors and External Conditions

How Situational Factors Influence Aggression

Aggression results from the interaction of the personal factors discussed above with external conditions that can either facilitate or impede aggressive behavior or violence. These situational factors can be divided into environments, settings, situations, and stimuli to demarcate a rough continuum from widespread to focal influences. Among the external factors that might promote aggressive behavior are (p. 552) (a) living in a society that encourages aggressive behavior (environment); (b) being in a war zone such as any of a number of Middle Eastern trouble spots (setting); (c) being caught up in the general chaos of a firefight or riot (situation); and (d) being attacked by an antagonist (stimulus).

Factors that might inhibit violence include (a) living in a peaceful and harmonious society (environment); (b) attending a Quaker religious service (setting); (c) being in the presence of loved ones or authorities who disapprove of aggression (situation); and (d) being lovingly embraced by a potential target of aggression (stimulus). The boundaries between these terms are not significant; the point is that a wide range of external factors and events helps determine whether or not an aggressive act takes place. The common denominator for these events, according to Monahan and Klassen (1982), is that they all occur outside our skins.

Situational influences involve times as well as places; much more violence occurs in New York City's Central Park between 2:00 and 4:00 A.M. on Sunday morning than from 2:00 to 4:00 P.M. on Sunday afternoon. Of course, personality and situational factors are not independent. Those peaceful people who flock to Central Park on a sunny afternoon generally shun it in the early morning hours, leaving it to the predators and police.

Contagion effects are also important. Berkowitz (1970) demonstrated an increase in violence following highly publicized aggressive crimes. We have already noted the fact that Seung-Hui Cho was influenced by the Columbine High School killings. In addition to his Virginia Tech massacre, there have been at least 25 high school shootings involving multiple victims in the United States as well as at least 9 mass school shootings in other countries (, 2007).

The circumstances and stimuli to which clients are exposed and the conditions in which they live are extremely important determinants of aggression. Cognitive expectancies interacting with situational realities can cause frustration, the major source of intrinsic instigation (Dollard et al., 1939). Environmental factors can moderate the relation of personality factors, such as empathy, to aggression (Rose & Feshbach, 1990). Given strong enough threat or provocation, almost anyone may become violent.

Since this book is about personality assessment, space does not permit a discussion of all the external factors that influence aggression. Among those that have been emphasized in the literature are ambient temperature (Anderson & Bushman, 2002; Baron & Ransberger, 1978; Megargee, 1977); architectural design (Newman, 1972); crowding (Megargee, 1977; Russell, 1983); the family, peer, and job environments; the availability of alcohol and of potential victims (Monahan & Klassen, 1982); and the behavior of antagonists, victims, associates, and bystanders (Megargee, 1993; Wolfgang, 1958). Perhaps the most widely discussed variable is access to weapons by either or both antagonists (Cook, 1982; MacDonald, 1975; Monahan & Klassen, 1982).

Assessing Situational Factors

In both prospective and retrospective assessments, clinicians must consider the influence of situational as well as personality factors. There is no substitute for familiarity with a client's various environments and living conditions. First-hand appraisals are the best source of information. This is done most easily in hospitals and prisons in which one is attempting to predict institutional violence. It is more difficult in community settings, but if home visits can be arranged they are invaluable. In most cases, however, we must rely on descriptions in case history material, police reports, and information gained in interviews with clients.

Compared with personality measures, there are few instruments for systematically assessing situational influences. An exception is the Correctional Institution Environment Scale (CIES; Moos, 1975), a 90-item instrument scored on nine environmental scales that is designed to be administered to inmates and staff. The CIES has been used more to evaluate the the effects of various program changes on the social climate of prisons rather than as a measure to be considered in analyzing the causes of institutional aggression.

In recent years, several instruments have been devised to assess bullying and identify bullies in schools using both self-and peer reports. However, their reliability and validity have not yet been well established (Cornell, Sheras, & Cole, 2006).

Bjørkly (1993, 1994) devised a situational “Scale for the Prediction of Aggression and Dangerousness in Psychotic Patients,” which is designed to predict the frequency and intensity of psychiatric patients' aggressive behavior in 29 different situations, both on the ward and off. Recent research (Bjørkly, Havik, & Løberg, 1996) has attested to its inter-rater reliability, but its validity is yet to be established, as is its applicability outside of Norway. Monahan and Klassen (1982) suggested that we (p. 553) investigate the circumstances that led people to commit aggressive acts in the past and determine whether they correspond to the situations they are likely to encounter in the future. We might also ascertain the environmental and situational factors associated with peaceful periods to help guide recommendations for future treatment or environmental manipulation.

The less we know about the settings in which clients will find themselves or the situations and stimuli they will face, the more difficult it is to make accurate predictions. Only in institutional settings, such as prisons and inpatient mental health units, where the environmental factors are relatively constant for all subjects, does it appear possible to make reasonably accurate predictions based only on personality factors (McGuire & Megargee, 1976).

Response Competition and Reaction Formation

An aggressive or violent act will be blocked if inhibitory factors exceed motivating ones. However, if all the forces favoring a particular response exceed those opposing it, that act is possible, at least as long as those conditions prevail. Before it can be carried out, however, all the possible responses, both violent and nonviolent, must compete with one another. The one with the highest reaction potential—that is, the greatest capacity to satisfy the most needs at the least cost—should be chosen.

Assessing Reaction Potential

In a retrospective analysis of aggressive behavior, it is obvious that the act that was actually performed had the highest reaction potential. If that act was socially or personally undesirable, and the clinical goal is to decrease the likelihood of a recurrence, other more satisfactory alternatives should be investigated. Why were these acts not selected? Were the inhibitions too great? Their chance of success too low? Did cognitive beliefs suggest that the aggressive act was the more honorable alternative? Did friends or onlookers encourage the aggressive behavior? The answers to such questions might indicate how the reaction potential of the objectionable behavior may be decreased and that of more acceptable responses increased.

In prospective assessments, the clinician's task is to try to determine the range of possible responses and estimate their relative reaction potential. Situational circumstances, such as whether or not certain interventions are attempted, may be critical. Instead of affixing a blanket label, such as “dangerous,” these analyses should help clinicians make more sophisticated contingent predictions of the likelihood that clients will engage in specified aggressive behaviors under various sets of circumstances.

Generalized Assessments of Aggression and Violence

While retrospective assessments entail detailed clinical evaluations of aggressive events and individuals, prospective studies typically involve screening groups of patients or offenders to identify those who are most likely to aggress in the future. Originally referred to as predicting “dangerousness,” these evaluations are now termed “risk assessment.”

Approaches to Risk Prediction

Subjective Judgment

In the 1950s and 1960s, diagnoses of dangerousness were made clinically by psychiatrists, psychologists, and case workers using whatever criteria their training and experience suggested. In the 1970s, researchers began examining the accuracy of these diagnoses by conducting follow-ups of psychiatric patients who had been labeled dangerous and subsequently released into the community. Official records such as arrest reports indicated that only 20–35% of these patients actually engaged in aggressive behavior after they had been released (Cool, Boucher, & Graffito, 1972; Steadman & Cocozza, 1974). More recent studies using more sophisticated assessments and improved research methods now suggest that the accuracy of short-term clinical predictions of violence among acute psychiatric patients may be as high as 50% (Borum, 1996; Monahan, 1996; Otto, 1992). This improved accuracy still risks classifying many nonaggressive people as potentially violent (“false positives”), especially in settings in which aggressive behavior is infrequent.

Clinical risk assessment has been criticized as being overly subjective and potentially influenced by illusory correlation, stereotypes, and hindsight bias (Towl & Crighton, 1995). This was illustrated by Cooper and Werner's (1990) investigation of the abilities of 10 psychologists and 11 case workers to predict institutional violence based on 17 variables in a sample of 33 male federal correctional institution inmates, 8 of whom (24%) were violent and 25 of whom (76%) were not. They found that interjudge reliabilities were quite low, averaging only .23 among pairs of judges. Pooled judgments were substantially more reliable than individual assessments. Accuracy was appalling; the psychologists' predictive (p. 554) accuracy averaged only -.08 (range = -.25 to + .22), while the case workers' mean accuracy was + .08 (range = -.14 to + .34). The main reason for the inaccuracy appeared to be illusory correlation, with judges often using cues that proved to be unrelated to the criterion.

Subjective classification procedures are difficult to document, which can result in a lack of oversight and accountability. Correctional facilities relying on subjective appraisals have been plagued by chronic “overclassification,” with prisoners being assigned to more restrictive conditions of confinement than necessary. In a series of cases, the courts held that subjective classifications were too often arbitrary, capricious, inconsistent, and invalid (Austin, 1993; Solomon & Camp, 1993). In Laaman v. Helgemoe (437 F. Supp. 318, D.N.H. 1977, quoted by Solomon & Camp, 1993, p. 9), the court stated that prison classification systems, “cannot be arbitrary, irrational, or discriminatory,” and in Alabama the court took over the entire correctional system and ordered every inmate reclassified (Fowler, 1976).

Personality Tests

Psychological tests developed in other contexts and for other purposes have also been used in risk assessment. The original MMPI and its successor, the MMPI-2, are the world's most widely used and researched clinical inventories.2 Megargee and Mendelsohn (1962) found that extremely violent and moderately violent male applicants for probation did not differ from nonviolent criminals and noncriminals on a dozen original MMPI scales especially designed to measure hostility and aggression. Megargee and Carbonell (1995) correlated a number of MMPI scales with measures of institutional adjustment and violence. The correlations, while significant, were generally too low to be of much value in prospective risk assessment, and multiple regression equations were not much better.

Bohn (1979) was able to reduce the incidence of serious assaults in a federal correctional institution 46% by using the MMPI-based offender classification system (Megargee et al., 1979, 2001) to identify those inmates most likely to be predatory and those most likely to be preyed upon so they could be housed in different dormitories. However, the MMPI-2 is better at assessing offenders' attitudes, mental health, emotional adjustment, and need for treatment or other professional interventions (“needs assessment”) than it is at estimating how dangerous they are (Megargee, 2006b).

The psychological test with the best track record with regard to violence risk assessment is Hare's (2003) PCL-R. The PCL-R was devised to assess the construct of psychopathy as originally delineated by Cleckley (1941/1976). Since 1980, an impressive array of empirical evidence from personality, physiological, and cognitive psychological research as well as from criminology and corrections has attested to the construct validity of the PCL-R. Barone 2004, p. 113) recently referred to the PCL-R as the “gold standard” for the measurement of psychopathy.

PCL-R assessments require a thorough review of the clinical, medical, and legal records, followed by a clinical interview in which a complete chronological case history is obtained. For research purposes, it is possible to compute PCL-R scores based only on (extensive) file data (Grann, Långström, Tengström & Kullgren, 1999), but this is not recommended (Meloy & Gacono, 1995).

The PCL-R consists of 20 symptoms of psychopathy, each of which is scored on a 3-point scale from 0 (absent) to 2 (clearly present). Inter-rater reliabilities average .86, and users are advised to base assessments on the average of two or more independent ratings whenever possible (Hare et al., 1990). Although Hare et al. (1990) regard the PCL-R as a homogeneous, unidimensional scale based on its average alpha coefficient of .88, there are two well-defined factors. The first reflects an egocentric, selfish interpersonal style with its principal loadings from such items as glibness/superficial charm (.86), grandiose sense of self-worth (.76), pathological lying (.62), conning/manipulative (.59), shallow affect (.57), lack of remorse or guilt (.53), and callousness/lack of empathy (.53). The items loading on the second factor suggest the chronic antisocial behavior associated with psychopathy: impulsivity (.66), juvenile delinquency (.59), and need for stimulation, parasitic lifestyle, early behavior problems, and lack of realistic goals (all loading .56) (Hare et al., 1990).

Reviewing a number of empirical investigations, both retrospective and prospective, Hart (1996) reported that psychopaths, as diagnosed by the PCL-R, had higher rates of violence in the community and in institutions than nonpsychopaths, and that psychopathy, as measured by the PCL-R, was predictive of violence after admission to a hospital ward and also after conditional release from a hospital or correctional institution. He estimated that the average correlation of PCL-R scores with violence in these studies was about .35. In their (p. 555) follow-up of 618 men discharged from a maximum security psychiatric institution, Harris, Rice, and Quinsy (1993) reported that, of all the variables they studied, the PCL-R had the highest correlation (+.35) with violent recidivism, and they included psychopath as defined by PCL-R scores 〉25, as a predictor in their Violent Risk Appraisal Guide. Rice and Harris (1997) reported that the PCL-R was also associated with sexual reoffending by child molesters and rapists. In their meta-analysis of 18 studies relating the original and revised Pals to violent and nonviolent recidivism, Salekin, Rogers, and Sewell (1996) found 29 reports of effect sizes ranging from 0.42 to 1.92 with a mean of 0.79. They reported, “We found that the PCL and PCL-R had moderate to strong effect sizes and appear to be good predictors of violence and general recidivism” (p. 203).3 Hart summarized it best when he concluded, “predictions of violence using the PCL-R are considerably better than chance, albeit far from perfect” (1996, p. 64). The Psychopathy Checklist-Screening version (PCL-SV; Hart, Hare, & Forth, 1994), a reduced 12-item version of the PCL-R more suitable for screening, has also been shown to relate to violent behavior (Douglas, Yeoman's, & Boer, 2005).

Objective Assessment Tools: Rationally Derived

A number of objective classifcation instruments have been created in recent years to eliminate the unreliability and subjectivity associated with clinical decision making (see Table 28.1). Some have been constructed rationally, others empirically. Authors of rationally constructed devices select variables that they believe are associated with aggression, violence, misconduct, or recidivism on the basis of clinical experience, psychological theories, and the findings in the empirical literature. For example, the Dangerous Behavior Rating Scale (Webster & Menzies, 1993) was based on the algebra of aggression model (Megargee, 1976) discussed earlier in this chapter, while the Level of Supervision Inventory (LSI) was guided by social learning theory (Bonta & Motiuk, 1985). Variable selection is also strongly influenced by practical concerns such as the types of data available in the client files and whether it is feasible to interview or test those being screened. Once the variables are selected and operationally defined, a coding scheme needs to be constructed that deals with issues such as missing data and personnel must be trained to code records reliably. Next, a scoring system must be devised that considers such issues as how to weight and combine the variables. Should an overall global score be computed or should a decision tree approach be used? Finally, cutting scores must be selected, or decision rules formulated, to assign subjects to categories differing in their estimated propensity for aggression and violence. Regardless of the methods employed, in a purely objective system the final decisions are based on the outcome of the instrument. If, as is often the case, staff can override the objective classification, subjective elements have reentered the system.4

As might be expected, the validity and utility of rationally derived devices varies greatly. The Federal Bureau of Prisons (BOP) and a number of state departments of corrections created objective instruments to indicate appropriate custody and supervision levels in correctional institutions (Austin, 1993; Brennan, 1987, 1993; Glaser, 1987). While not specifically designed to predict aggression per se, the potential for violence was, obviously, an important consideration. The model based security level classifications on the expected length of incarceration, offense severity, type of prior commitment, history of violence or escape attempts, and types of detainers (Kane, 1993). However, Proctor 1994, who evaluated Nebraska's adaptation of the BOP model, noted it accounted for only 3% of the variance in institutional adjustment and concluded, “The results regarding the predictive validity of the Nebraska model suggest that the classification model was not a valid instrument for predicting institutional adjustment” (p. 267).

Much better results have been obtained with the LSI (Bonta & Motiuk, 1985) and its successor, the Level of Service Inventory-Revised (LSI-R; Andrews & Bonta, 1995). Originally designed to screen inmates for possible placement in Canadian correctional halfway houses, it is now widely used in probation offices and prisons throughout Canada and has been researched and utilized in Australia (Daffern, Ogloff, Ferguson, & Thomson, 2005), England and Wales (Hollin & Palmer, 2006; Palmer & Hollin, 2007), Germany (Dahle, 2006), and even the US (Schlager & Simourd, 2007) despite the fact that Gendreau, Goggin and Smith (2002, p. 423) complained that American psychologists “have generally not heard of it.”

The LSI and LSI-R are interview-based instruments that evaluate offenders on 54 two-point scales covering 10 areas: (a) criminal history, (b) education/employment, (c) finances, (d) family/ marital, (e) accommodations, (f) leisure/recreation, (p. 556) (p. 557) (g) companions, (h) alcohol/drug, (i) emotional/personal, and (j) attitude/orientation. It thus utilizes both static and dynamic information. Studies of the LSI have reported adequate reliability and significant associations of LSI total scores with success or failure in institutional settings, on probation and parole, and with general recidivism among both male and female offenders (Catchpole & Gretton, 2003; Girard & Wormith, 2004; Hollin & Palmer, 2006; Kroner & Mills, 2001; Palmer & Hollin, 2007; Simourd, 2004). However, the LSI-R's associations with violent recidivism are less robust than those with general recidivism (Daffern et al., 2005; Gendreau et al., 2002). Girard and Wormith (2004) recently added a new specific/risk section to the latest “Ontario” revision of the LSI to improve its assessment of aggressive behavior.

Table 28.1 Objective devices

1. Instruments devised for use in adult correctional and forensic settings


A 10-item clinical scale that combines with the VRAG to form the VPS (Webster & Polvi, 1995)

Dangerous Behavior Rating Scale

Based on Megargee's (1982, 1993) algebra of aggression model (Webster & Menzies, 1993)


Comprised of 20 ratings in three categories: historical, clinical, and risk management (Webster, Douglas, Eaves, & Hart, 1997; Douglas & Webster, 1999)

Level of Supervision Inventory (LSI and LSI-R)

Interview-based instruments that evaluate offenders in 10 areas for probation and halfway house placement (Bonta & Motiuk, 1985)

Lifestyle Criminality Screening Form (LCSF)

A 14-item scale designed to identify those career criminals who account for an excessive amount of antisocial behavior (Walters, White, & Denney, 1991)

Offender Group Reconviction Scale (OGRS)

A criminogenic reoffending scale based on criminal history and demographic variables (Copas & Marshall, 1998)

Risk Assessment Scale for Prisons (RASP)

Devised to forecast violence in US prisons (Cunningham & Sorenson, 2006; Cunningham, Sorenson, & Reidy, 2005)

Self-Appraisal Questionnaire (SAQ)

A 72-item yes/no instrument aimed at predicting violent and nonviolent recidivism (Loza, Dhaliwal, Kroner, & Loza-Fanous, 2000; Loza & Loza-Fanous, 2003)

Short-Term Assessment of Risk and Treatability (START) scale

Designed to guide the multidisciplinary assessment of forensic mental health inpatients (Nicholls, Brink, Desmarais, Webster, & Martin, 2006; Webster, Nicholls, Martin, Desmarais, & Brink, 2006)

Violence Prediction Scheme (VPS)

Comprised of the ASSESS-LIST and the VRAG (Webster, Harris, Rice, Cormeier, & Quinsey, 1994)

Violence Risk Assessment Guide (VRAG)

A record-based assessment tool used to sort mentally disordered offenders into nine categories based on their propensity for violence (Harris, Rice, & Quinsey, 1993)

Violence Risk Scale (VRS)

Combines both static and dynamic variables including ratings of clients' treatment progress (Wong & Gordon, 2006)

2. Instruments devised for risk assessments with juveniles and youths

Early Assessment Risk List for Boys (EARL-B) and Early Assessment Risk List for Girls (EARL-G)

Structured clinical checklists designed for the professional judgment of risk for aggressive and disruptive behaviors among boys (Augimeri, Koegl, Webster, & Levene, 2001) and girls (Levene, Augimeri, Pepler, Walsh, Webster, & Koegl, 2001)

Structured Assessment of Violence Risk Level in Youth (SAVRY)

Based on the HCR-20 for adults (Borum, Bartel, & Forth, 2002; Catchpole & Gretton, 2003)

Youth Level of Service/Case Management Inventory

Based on the LSI, has 42 items assessing eight criminogenic factors (Hoge & Andrews, 2002)

3. Instruments designed to assess violence among psychiatric inpatients

Classification of Violence Risk (COVR)

An interactive software program that provides a statistical estimate of the likelihood of violence based on chart and interview data (Monahan et al., 2006)

Multiple Iterative Classification Tree (ICT)

An actuarial decision-tree approach based on the MacArthur risk assessment studies for use in planning discharge with acutely ill civil inpatients (Monahan et al., 2005)

Suicide and Aggression Survey (SAS)

An interview-based instrument for adolescent and adult psychiatric patients (Korn et al., 2006)

Violence Screening Checklist (VSC)

Uses of demographic, case history, and diagnostic data to predict physical attacks among civilly committed inpatients (McNiel, 1988; McNiel & Binder, 1994)

4. Tools devised to predict sexual reoffending and recidivism

These tools were constructed following the passage of legislation allowing for the continued post-sentence detention and treatment of sex offenders deemed likely to offend:

Estimate of Risk of Adolescent Sexual Offence Recidivism (ERASOR)

Actuarial instrument aimed at adolescents (Worling & Curwen, 2001),

Minnesota Sex Offender Screening Tool-Revised (MnSOST-R)

Actuarial instrument based on file information. Better at predicting general than sexual recidivism (Epperson, Kaul, & Hesselton, 1998)

Multifactorial Assessment of Sex Offender Risk for Recidivism (MASORR)

Clinical ratings of factors empirically associated with sexual reoffending in literature including PCL-R (Barbaree, Seto, Langston, & Peacock, 2001)

Rapid Risk Assessment for Sexual Offender Recidivism (RRASOR)

Brief actuarial scale (Hanson, 1997)

Risk for Sexual Violence Protocol (RSVP)

(Hart, Kropp, Laws, Klaver, Logan, & Watt, 2003)

Sex Offender Risk Appraisal Guide (SORAG)

(Quinsey, Harris, Rice, & Cormier, 1998)

Sexual Violence Risk-20 (SVR-20)

Instrument used to assist structured professional judgment (Boer, Hart, Kropp, & Webster, 1997)


Ten items designed for adult males who have committed at least one prior sex offense (Barbaree, Seto, Langston, & Peacock, 2001; Hanson & Thornton, 1999)

5. Instruments designed to identify potential perpetrators of domestic violence

Ontario Domestic Assault Risk Assessment (ODARA)

Designed to predict further assaults against domestic partners by known male batterers (Hilton et al., 2004)

Spousal Assault Risk Assessment Guide (SARA)

Based on VRAG and ASSESS-LIST (Kropp, Hart, Webster, & Eaves, 1994).

Objective Assessment Tools: Actuarially Derived

Whereas rationally constructed instruments try to capture the judgments of classification experts and apply them in a standard fashion, actuarial tools are derived by selecting items that previous research has shown are empirically related to the behavior in question, such as institutional misbehavior or recidivism. These “risk factors” are then combined into a predictive scheme. Some investigators use multiple regression equations or weighted discriminant functions, some use simple additive models in which points are assigned for each risk factor, and some use decision trees. These schemes seem to work best in correctional mental health facilities, which typically have more data available, including psychological evaluations, than ordinary correctional institutions. It is generally agreed that, as a group, actuarially derived objective instruments outperform those that are rationally constructed (Barbaree, Seto, Langston, & Peacock, 2001; Dawes, Faust, & Meehl, 1989; Grove & Meehl, 1996; Grove, Zald, Hallberg, Lebow, Snitz, & Nelson, 2000; Kroner et al., 2007). However, in the area of risk assessment, it appears that the best rational and actuarial devices are comparable in their validity (Grann, Belfrage, & Tengström, 2000).

The best-established actuarial instrument for the prediction of violent recidivism is the Violence Risk Appraisal Guide (VRAG; Harris et al., 1993), which was derived from a population of 618 violent (p. 558) offenders at a maximum-security psychiatric institution, 191 of whom (31%) engaged in further violence after their eventual release. The clinical records of these “violent failures” were combed, coded, and compared with those of the 427 violent offenders who did not subsequently engage in violent recidivism. Multivariate analyses identified 12 variables from the 50 or so studied which significantly differentiated the two criterion groups. They included three history variables (elementary school maladjustment, separation from parents before age 16, and never marrying), four clinical history variables (history of alcohol abuse, DSM-III diagnoses of schizophrenia or personality disorder, and score on the PCL-R), two overall criminal history variables (record of property offenses and prior failures on conditional release), and three factors regarding the index offense (injuries to the victim, gender of victim, and age of offender at the time of the offense). Interestingly, the PCL-R was the variable most closely related to violent recidivism. These 12 variables were differentially weighted (with the PCL-R receiving the highest weight) and combined to yield a total VRAG score which was used to assign the subjects to nine categories ranging from the lowest to the highest chance of recidivism (Harris et al., 1993).

Because the VRAG consists only of unchanging static items, Webster and Polvi (1995) created the ASSESS-LIST, a device consisting of 10 more dynamic clinical variables: antecedent history, self-presentation, social and psychosocial adjustment, expectations and plans, symptoms, supervision, life factors, institutional management, sexual adjustment, and treatment progress. Together, the VRAG and ASSESS-LIST comprise the Violence Prediction Scheme (VPS; Webster, Harris, Rice, Cormier, & Quinsey, 1994).

Actuarially derived tools should be cross-validated on new independent samples before being used, and instruments devised in one setting or locale should be checked for accuracy before they are adopted elsewhere (Craig, Beech, & Brown, 2007). The VRAG has been successfully cross-validated on new samples of serious mentally disordered offenders by its creators and independent researchers (Douglas et al., 2005; Grann et al., 2000; Harris, Rice, & Cormier, 2002; Harris et al., 1993; Kroner & Mills, 2001; Loza & Dhaliwal, 1997; Quinsey, Harris, Rice, & Cormier, 1998; Rice & Harris, 1994, 1995).

Given its reliance on psychiatric diagnoses and psychological factors involved in previous violence, it is questionable whether the VPS could be applied in many correctional settings or to patients who have no prior history of violence.

Structured Professional Judgment

Whether they are rationally or actuarially derived, the essence of objective assessment tools such as the LSI-R and the VRAG is that decisions regarding the risks for aggression posed by those being assessed are based entirely on the scores they obtain on the instruments or the classifications they receive from the decision tree. In “structured professional judgment” (SPJ), objective tools are used to guide clinical judgments to a greater or lesser degree (Douglas et al., 2005).

A number of SPJ instruments have been developed (Douglas et al., 2005).5 Of these, the best known and most widely used is the rationally constructed HCR-20 (Douglas & Webster, 1999; Webster, Douglas, Eaves, & Hart, 1997). The HCR-20 is comprised of 20 records-based ratings in three categories: historical, clinical, and risk management. The ten historical (H) items are similar to the items on the VRAG. They include history of (a) previous violence, (b) young age at first violent incident, (c) relationship instability, (d) employment problems, (e) substance abuse (f), history of major mental illness, (g) psychopath as measured by the PCL-R, (h) early maladjustment, (I) personality disorder, and (j) prior supervision failure (Douglas & Webster, 1999).

The five clinical (C) items reflecting current emotional status are (a) lack of insight, (b) negative attitudes, (c) active symptoms of major mental illness, (d) impulsivity, and (e) unresponsiveness to treatment.

The five risk management (R) items are (a) plans lacking feasibility, (b) exposure to destabilizers, (c) Lack of personal support, (d) lack of compliance with remediation attempts, and (e) stress (Douglas & Webster, 1999). These dynamic C and R items, which can change to reflect a client's current situation, are the clearest difference between the HCR-20 and instruments that are based exclusively on historical or file data.

Because it is designed to guide structured clinical judgments, the HCR-20 does not have recommended cutting scores or algorithms that categorize people. Instead, it produces numerical scores on each of its three scales as well as a total score that clinicians are encouraged to consider when deciding whether people are at low, medium, or high risk of violent offending (Douglas et al., 2005). Nevertheless, a (p. 559) number of researchers have investigated the relationship between HCR-20 scores and various measures of institutional misconduct and recidivism as well as both sexual and nonsexual violent offending and reoffending. These studies indicate that the HCR-20 scales have areas under the curve (AUCs), correlations, and effect sizes comparable to the LSI-R, PCL-R, and VRAG (Douglas & Webster, 1999; Douglas et al., 2005; Grann et al., 2000; Kroner & Mills, 2001). In some of these studies, the static historical items have the highest relations to the criteria, in others the dynamic clinical and risk factors.

Douglas et al. (2005) also investigated how successfully the HCR-20 guided structured judgments of low, moderate, or high risk for violence. They reported that 19.1% of the low, 58.8% of the moderate, and 85.7% of the high groups were subsequently violent.

Issues in Prospective Risk Assessment

The development of objective risk assessment tools has made the prediction of aggressive behavior and violence much more accurate than was the case with the previously employed subjective appraisals (Borum, 1996; Monahan, 1996). That said, how useful are these devices in applied settings?

Clearly, there are limitations on their ability to predict dangerous behavior. First, these instruments are not specific to aggression and violence. The PCL-R assesses psychopathy, but not all psychopaths are violent and not all violent individuals are psychopathic. The HCR-20, LSI-R, and the VRAG/VPS all reflect other types of antisocial or illegal behavior such as general recidivism and insitutional misconduct as well as the aggressive or violent behavior which is the focus of this chapter.

Second, the best objective instruments, including the HCR-20, LSI-R, PCL-R, and VRAG/VPS, all require an extensive array of up-to-date information about each person being assessed including mental health data and an individual interview.6 This limits their utility to settings with the records and resources required to rate the various items. With the exception of the LSI-R, they generally appear to have been used in clinical settings on emotionally disturbed inpatients with a history of violent behavior.

A third limitation is the fact that these devices all focus on the characteristics of those being assessed, their past behavior, demographic characteristics, emotional adjustment and the like, while ignoring the situational factors that might influence their behavior (Klassen & O'Connor, 1988; Moos, 1975). Thus they are better able to identify habitually violent, mentally disturbed, or undercontrolled aggressive individuals than those who are overcontrolled or responding to situational provocations.

Fourth, objective instruments typically omit “protective” or ameliorative data that might mitigate the risk of aggression (Douglas et al., 2005). They typically include variables, such as prior felonies, that are associated with negative outcomes while overlooking positive factors, such as marketable employment skills or a positive family situation, which might decrease the risk of antisocial behavior.

Fifth, until proven otherwise, objective risk assessment devices, especially those that were actuarially derived, should only be used in those settings in which they were created. For example, Borum 1996, p. 994) noted that a diagnosis of schizophrenia is positively associated with violence in one model and negatively in another. He suggested the discrepancy stems from differences in the settings where the devices were developed. Kroner et al. (2007, p. 907) stated that, “traditional risk-assessment instruments might not adequately predict sexual recidivism in some offenders.” They concluded that specialized instruments are required to predict sexual reoffending.

When it comes to predicting aggressive or violent behavior, itisgenerally agreedthatthese objective tools should only be applied to individuals who are at a high risk for violent offending because they have already behaved violently or threatened violence (Klassen & O'Connor, 1988; Otto, 2000), and most of the research with these instruments has been conducted in such populations (Borum, 1996; Kroner et al., 2007). The purpose of this caveat is to guarantee a sufficiently high incidence or “base rate” of violence to permit reasonably accurate prediction. The closer the incidence of aggressive behavior is to 50%, the greater the potential contribution that a predictive tool can make. However, the more infrequent the behavior, the greater the number of false positives—nonviolent individuals incorrectly labeled violent—we can expect. Indeed, when violence rates are as low as 5% or 10%, we will make more errors using an instrument with a high false-positive rate than we would by simply assuming no one will be violent (Brennan, 1993; Kamphuis & Finn, 2002; Klassen & O'Connor, 1988; Meehl & Rosen, 1955; Megargee, 1976, 1981; Wollert, 2006; see Chapter 8).

As Otto 1992, p. 128) noted, when assessing dangerousness, incorrect predictions are inevitable, the most common errors being false positives. For this reason, it is important to consider the (p. 560) consequences of incorrect classifications (Megargee, 1976). In Bohn's (1979) study, those prisoners labeled “potential predator” or “potential prey” based on their MMPI-based classifications were simply separated by being assigned to different dormitories. Their designations had no impact on their programming or other conditions of confinement. With such a benign outcome, Bohn could tolerate large numbers of false positives in both categories. However, in many cases, the consequences for false positives can be quite serious. For example, those diagnosed as dangerous sex offenders may be civilly committed or subjected to preventive detention over and above their criminal sentence; those released may be forced to register with the police, denied certain types of employment, and restricted with regard to where they can live (Janus, 2003; Kroner et al., 2007).

Although the emphasis in risk assessment is on diagnosing the most dangerous offenders, the greater contribution of these classification tools has been to identify low-risk individuals (true negatives) who can be placed in less secure settings or released to the community (Austin, 1993; Glaser, 1987; Solomon & Camp, 1993). When making subjective predictions of violence, assessors are often overly conservative, placing too many individuals in higher-than-necessary risk categories (Heilbrun & Heilbrun, 1995; Monahan, 1981, 1996; Proctor, 1994; Solomon & Camp, 1993). This is not surprising. There is little public concern over false positives who may be retained in overly restrictive mental health or correctional facilities, but there is an understandable outcry when a future mass murderer such as Charles Whitman or Seung-Hui Cho is assessed as not dangerous.

Reducing the extent of overclassification is especially important in criminal justice and correctional settings. First, it is the correct thing to do. The courts have consistently ruled that criminal offenders have the right to be maintained in the least restrictive settings consistent with maintaining safety, order, and discipline. Second, less restrictive settings are more economical. Confining a criminal offender in a maximum-security institution costs $3,000 a year more than a minimum-security facility and $7,000 more than a community setting. Third, all residents benefit because more programming is possible in less restrictive correctional settings, and the deleterious effects of crowding are diminished (Proctor, 1994).

Perhaps the greatest limitation on the utilization of objective risk assessment devices is the reluctance of clinicians to rely on such tools. The more complex the statistical procedures, the less likely decision makers are to use them (Brennan, 1993). In his classic paper, “Why I no longer attend case conferences,” Paul Meehl (1977) lamented the tendency for clinicians to place more faith in their subjective impressions than they do in base rates or the results of objective instruments. In a recent risk assessment study, Kroner and Mills (2001) found that experienced clinicians provided with base rate data apparently ignored them when estimating the likelihood of violent offending. As a result, they did no better than a contrast group of clinicians who had no information on base rates.

Hilton and Simmons (2001) reviewed the factors associated with decisions made by the Ontario Review Board on whether mentally disordered offenders charged with serious, usually violent, offenses should be detained in maximum security. VRAG scores, which were provided to the members of the board, were not related to the eventual security-level decisions. The most important single variable was the testimony of the senior clinician, although criminal history, psychotropic medication, institutional behavior, and even the physical attractiveness of the patient also played a role. They concluded, “contrary to current optimism in the field, actuarial risk assessment had little influence on clinical judgments and tribunal decisions about mentally disordered offenders in this maximum security setting. … It is apparent … that simply creating actuarial instruments and making the results available to decision makers does not alter long-established patterns of forensic decision making” (Hilton & Simmons, 2001, pp. 402, 406).


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                                                                                                                                                                                                                                                                                                                                                                                      (1.) Although we have only considered human aggression, there is also a vast literature on animal aggression, which further complicates definitional issues. Because this book concerns clinical personality assessment, discussion has been limited to human aggression and violence, but readers should keep in mind that a comprehensive theory of aggressive behavior should be applicable to animal as well as human behavior.

                                                                                                                                                                                                                                                                                                                                                                                      (2.) Gendreau et al. (2002 p. 422) recently complained, “Is there an offender anywhere in North America who has not at some point been administered the MMPI/MMPI-2?”

                                                                                                                                                                                                                                                                                                                                                                                      (3.) Salekin et al. (1996, p. 211) hailed the PCL-R as being “unparalleled as a measure for making risk assessments.” Gendreau et al. (2002) took umbrage at this effusive praise and took 30 journal pages to explain why the LSI-R was superior to the PCL-R. Hemphill and Hare (2004) took offense at Gendreau et al.'s (2002) criticisms and spent 41 pages explaining why the PCL-R was at least as good as the LSI-R for predicting criminal justice criteria, even though the PCL-R was designed to assess the construct of psychopathy rather than predict recidivism.

                                                                                                                                                                                                                                                                                                                                                                                      (4.) The issue of when or if clinicians should be able to override the objective classification has been hotly debated for over half a century beginning with Meehl's (1957) classic article, “When shall we use our heads instead of the formula?”

                                                                                                                                                                                                                                                                                                                                                                                      (5.) According to Douglas et al. 2005, the instruments designed for SPJ include the EARL-20B and EARL-20G, the HCR-20, the RSVP, the SARA, the SAVRY, and the SVR-20 (see Table 28.1).

                                                                                                                                                                                                                                                                                                                                                                                      (6.) The LSI-R and PCL-R both require interviews, and the HCR-20 and the VRAG both include the PCL-R.