There are many books dealing with the problem of aggression in man. The topic, however, covers too many types of violent and aggressive behaviors to be very useful. The subject ranges too far afield. It covers such varied aspects as simple assault to murder to mass murder to warfare, colonialism, and imperialism. The subject has to be narrowed if any real progress is to be made in elucidating the topic.

Another problem with the general approach to aggression in human beings is that the topic is too intimately tied to politics. Liberals have a revulsion to considering the role of biology in human aggression. They fear that any consideration of biology will give approval to such hateful activities as war. Despite liberal suspicions against evolution and biology, however, the evolution of man is a story of trying to control aggressive tendencies rather than to express them. The expression of violence in humans is an example of failing to control man's more primitive heritages.

There are many reasons why humans engage in violence. But since we are stressing the physiological reasons for human behavior in this book the topic becomes narrowed somewhat. To narrow the topic of aggression, chapter 14 concentrates specifically on the topic of psychopathology. The next chapter deals with the subject of rape that has increasingly come to be seen as a problem of violence.

Incidents of violence were once considered simply as examples of "hot temper," but neuroscientists have now discovered physical mechanisms that can result in aggression (Restak, 1988:277). Brain damage, hormonal imbalance, mental illness, and many other physical problems can distort a person's perceptions, so that trivial incidents are seen as major threats. There are, of course, many types of violence with many different causes. Much of this violence actually occurs in the home. In the home the offender is usually a male aggressor against a wife, female child or stepchild. Studies indicate that the aggressor often suffers from psychological disorders: personality disorders, maladaptive behaviors, and psychoses, including manic depressive and schizophrenic behavior (Lystad, 1985:62).

Cummings (1985) has delineated at least ten separate possible physiological causes of violence in humans. But even Cummings admits that violence is the result of many factors, such as neurological, toxic, characterological, social, and situational factors. Most of the physiological causes of violence, however, seem to center around the limbic system. Among the physiological causes are epilepsy, a limbic system dysfunction known as episodic dyscontrol syndrome, frontal lobe damage, orbitofrontal injury involving the limbic system, metabolic disorders, toxic disorders such as those involved in alcohol intoxication, persecutory delusions, attention-deficit disorder leading to anti-social personality disorder, and psychoses. Brain tumors that impact the limbic system can also stimulate violent behavior. An example is Charles Whitman, who from the main tower at the University of Texas at Austin shot numerous residents of the university and town. A possible endocrine source for violence in humans is elevated testosterone levels. However, testosterone studies are not always consistent and more study is needed. A safe summary is that endocrine factors lower the threshold for violence in already predisposed individuals (Cummings, 1985:132).

Important sources of violence in women are endocrine disorders. D'Orban and Dalton (1980, cited in Cummings, 1985:131-132) found that 44 percent of 50 women charged with violent crimes committed their offenses during the perimenstrual period and that there was a significant lack of offenses during the ovulation and postovulation phases of the menstrual cycle.

Disturbances in the brain among violent patients often show up on EEG readings. Some of the EEG abnormalities are generalized slowing, focal slowing, and epileptiform abnormalities. These findings indicate that brain dysfunction is common among violent offenders (Cummings, 1985:128). EEG changes are more common in subjects who commit acts of violence than in those with nonviolent crimes and are more frequent in those with repeated violence than those with isolated violent acts. When the violence had no apparent motive, there was also an increased chance of finding an EEG abnormality compared to violence that had been provoked.

Despite the many EEG abnormalities, there does not appear to be an aggression center per se. Rather there is a network of neuronal connections, beginning in the limbic system and traveling downstream through the hypothalamus and into the brainstem (Restak 1984:132-133 & 279). The sites that are most important in triggering violence are the frontal and prefrontal areas, and the amygdala, the hippocampus, and the hypothalamus, which are part of the limbic system along with the central gray of the midbrain, and the brain stem. Electrical stimulation of any of these structures can produce affective aggression. According to Groves and Schlesinger (1982:447), removal of the amygdaloid nuclei in monkeys directly affects their dominance hierarchy. In humans an amygdalectomy in patients who exhibit uncontrolled destructive behavior results in marked improvement, but patients lack initiative and enthusiasm. Other symptoms of amygdalectomized patients are marked weight gain and an increase in sexual drive. Adrenocorticotrophic hormone (ACTH) has also been implicated in aggressive behavior. If mice are adrenalectomized they become less aggressive.

The posterior region of the hypothalamus is especially important in the study of violence (Restak, 1984:128). The posterior region regulates the emergency responses required when an animal is threatened. Stimulation in the posterior area of a cat makes it bad-tempered, and will start to spit and will even attack humans.

The cerebral hemispheres are largely responsible for inhibition of aggressive connections. Alcohol can diminish this control. Mind-altering drugs can have similar effects. PCP ("angel dust") especially is associated with sudden impulsive outbursts. Such chemicals exert their primary effect on the hippocampus and cerebral cortex, sometimes leading to a massive discharge of aggression.




Psychiatrists have labeled the personality disturbance most likely to produce repeated violence as a habitual behavioral style as antisocial personality disorder (ASP), a term that has superseded the older term of psychopath. The antisocial personality disorder usually originates in childhood or early adolescence as a conduct disorder, and then continues into adulthood. Sociologists often have their own theories and refer to these people as sociopaths. Social causes of psychopathy include early deprivation, parental rejection, and loss of parents (McCord, 1982:chapter 6).

Childhood abuse is often connected with psychopathology (Rosenhan and Seligman:441). Being a victim of sexual abuse as a child appears to be a factor in whether or not one becomes a sexual abuser (Lystad, 1985:63) Swift (1977) reports that a large proportion of males who abuse children have been sexually abused as children. She finds the adult offenders as both sexually ignorant and socially immature. Nevertheless, sociologists should not forget that these social influences are translated by the mind and this is a physiological process.

Regardless of the source of the damage, however, the more important aspect of psychopathology is how damaged these people are physiologically. These people are not the same as those people who have few or no violent episodes. Personality disorders are long-lived.


Neugebauer, et. al. (1980:67) estimates that about 7 percent of the population suffer from antisocial personality disorder. This statistic overlaps considerably with alcohol and drug problems, thereby making the statistic more difficult to derive.


Types of Psychopaths

There are several subtypes of ASP. Hare's recent work suggest two types of ASP, one based on personality factors, the other on environmental factors (Hesselbrock, et al. 1992:189). Quay (1986:12) has identified two different types of children with antisocial personality disorders. He calls the two types the undersocialized and socialized aggressive conduct disorders. In the undersocialized aggressive conduct disorder, there are the following characteristics: fighting, hitting, assaultive behavior; disobedience and defiance; temper tantrums; destructiveness; impertinence, "smart-aleck" impudence; being uncooperative, resistant, inconsiderate, stubborn; attention seeking, "showing- off"; dominates, bullies, threatens; disruptive, interrupts, disturbs others; boisterous, noisy; irritability, "blows up" easily; negative, refuses directions; restless; untrustworthy, dishonest, lies; and hyperactivity. The socialized aggressive conduct disorder has the following characteristics: having "bad" companions; truancy from school and home; stealing in company with others; belonging to a gang; loyalty to delinquent friends; staying out late at night; stealing at home; and lying and cheating. In this pattern involvement with peers takes on an illegal aspect or, at least, norm-violating behavior is central to the group behavior. Its characteristics, considered from a developmental perspective, suggest that it is mainly a phenomenon of older childhood and adolescence, rather than younger children.

Characteristics of Psychopathology:

1) Inability to Learn from Negative Experiences

There is evidence that psychopaths suffer from an inability to learn from painful experiences. In effect, punishment or threat of punishment does not seem to influence their behavior. These deficits are prominent in the area of avoidance learning. Cleckley (1964) observed that psychopaths especially failed to learn from punishing experiences, and as a result, had poor judgment. An old-fashioned word that is no longer used because of its moralistic connotations is "moral imbeciles." However, this word is useful in pointing out the seeming inability of psychopaths to learn how to behave themselves from negative reinforcement.

An alternative hypothesis is that psychopaths may have suffered physical ailments, such as encephalitis, epilepsy, or birth damage, that affected their neural structures and made them relatively incapable of internalizing the inhibitions that their particular society dictates. Also possible is that psychopaths suffer sufficient environmental deprivation to affect their neural structure.

2) Boredom

Dr. Richard Howard at Queen University in Belfast (cited in Restak 1988:312) found evidence of low cortical arousal in convicted murderers and mentally abnormal offenders who had committed acts of extreme violence. Cortical activity was depressed, as if they were in a generally sleepy state. There are also anomalous brain wave patterns in from 50-60 percent of the subjects. Howard believes these findings are related to trauma incurred during the perinatal period.

Secondary characteristics of psychopaths are a tendency to crave excitement, to be impulsive, and, of course, to be often aggressive (McCord, 1982:27-31). Psychopaths are emotionally flat and chronically under-aroused, so punishment is not as noxious to them. Their autonomic nervous systems may be so sluggish that they do not feel anxious about committing a prohibited act (Restak, 1988:312). By committing bad deeds, psychopaths may actually be seeking stimulation in order to elevate their low arousal level.

3) Learning Disabilities

Robert Hare of the University of British Columbia (cited in Restak, 1988) has found that psychopaths do not process words on the left side of the brain as the rest of us do. Rather their language processing seems equally balanced between the right and left brain. This seems to indicate laterality problems in the brain.

Subjects with ASP have poorer performance on several measures of cognitive functioning including the Luria Motor Task 22, Trails A, verbal IQ and Porteus Mazes errors than nonASP subjects (Hesselbrock, et al. 1992:186). These findings suggest that young males with the ASP risk factor perform less well on measures of higher level motor coordination, response inhibition, visual motor integration, and verbal abstraction than nonASP young men.

The Role of Heredity

Antisocial personality disorder often arises from genetic sources. Dr. Dorothy Otnow Lewis (cited in Restak, 1988:282), Professor of Psychiatry at the New York University School of Medicine, found that delinquent boys who later became murderers showed patterns of aggressive and sometimes violent behavior in childhood, as well as other factors: close relatives with psychotic illnesses, severe parental abuse, major neurological impairments, and a history of head injury.

Biological children of psychopathic parents more often exhibit a psychopathic syndrome than do offspring of nonpsychopathic parents. Therefore, hormonal excretions that relate to psychopathy may have a genetic link. The production of epinephrine (adrenaline) is severely limited in psychopaths. This connects with the ever present problem of boredom faced by psychopaths (McCord, 1982:138-139 and 24). According to Rosenhan and Seligman (514-5), an inherited biological disability interferes with learning to inhibit aggressive behaviors and may well be associated with deficits in autonomic arousal.


In many incidents involving criminal activity the perpetrator has problems with at least two aspects of motivational behavior. There is a problem with both the go system and the stop system of motivation. The problem with their go system is that they have a disturbance in what they want or desire, and the problem with their stop system is that the system is deficient, and there is less of a "conscience" to prevent them from committing the deviant act. Both these aspects can be seen in criminal psychopaths.

There are patterns common to many habitually violent individuals, including frequent low blood sugar levels and abnormal EEG readings. Although abnormal clinical EEGs are present in only 10-15 percent of the general adult population, 48-70 percent of aggressive psychopaths are reported to have EEGs that are judged to be abnormal. One study reported that 50 percent of a group of children displaying violence and severe behavior disorders had abnormal EEGs. These abnormalities were not of the type ordinarily associated with epileptic seizures (Surwillow, 1990:93). Reduced P3 amplitudes have been found among ASP subjects at several frontal leads. ASP subjects had reduced P3 amplitudes at the Fp2 and F4 sites as well as at Fz and F8 (Hesselbrock, et al. 1992:187).

A common reported finding in the EEGs of aggressive psychopaths is the presence of abnormally slow activity in the waking record. A possible hypothesis is that the abnormally slow EEG activity results from a failure in normal development of the central nervous system, and that aggressive behavior is a reflection of what has been called functional cortical retardation (Surwillow, 1990:93-94). Severely aggressive children appear to have EEGs that are characteristic of children who are younger in age than they are, which corresponds to the "maturation-retardation" hypothesis. There are many possible causes of slowed development. In the womb, the mother's poor nutrition, alcoholism, or tobacco use can lead to abnormalities in fetal brain development. Problems can also occur during birth such as oxygen deprivation (Restak, 1988:312).

Of course, within the limbic system, neurotransmitters are very important. Animal studies have shown that a decrease in the neurotransmitter serotonin coincides with a rise in aggressiveness. An increase in norepinephrine and dopamine leads to the same result (Restak, 1984:140). The chemical 5- hydroxyindoleacetic acid (5-HIAA) is the principal metabolite of serotonin measured in cerebro-spinal fluid (CSF). Serotonergic mechanisms may inhibit aggressive behavior by way of the serotonergic input to the central grey. It is consistent with these data that 5-HIAA levels in human CSF correlate negatively with a history of aggressive behavior directed towards either others or oneself (that is, suicide attempts). Low 5-HIAA levels have also been found among criminals, especially those who have been incarcerated for violent and aggressive behavior.

In psychopaths there is an absence of the emotional or affective component of conscience. This may be connected to a lack of serotonin in the system. Linnoila et al. (1983, cited in Roy, 1990:49) examined CSF 5-HIAA levels (metabolite of serotonin) among 36 male murderers and attempted murderers. Low levels seem to be associated with poor impulse control. The study found 27 of the 36 to be impulsive as opposed to nonimpulsive. The impulsive patients had either intermittent explosive or anti-social personality disorder, whereas the nonimpulsive patients had either paranoid or passive aggressive personality disorder. The authors found that CSF 5-HIAA levels were significantly lower among the two groups of impulsive violent offenders than among the nonimpulsive violent offenders. Moreover, the 17 offenders (14 impulsive and 3 nonimpulsive) who had committed more than one violent crime had CSF 5-HIAA levels significantly lower than those found among offenders who had committed only one violent crime. The violent offenders who at some time had attempted suicide were also found to have significantly lower CSF 5-HIAA levels than the violent offenders who had never attempted suicide.

Rogeness, Hernandez, Macedo, and Mitchell (1982, cited in Quay, 1986:50) have contrasted socialized, undersocialized, and normal control children on four biochemical factors measured in blood plasma: dopamine-beta-hydroxylase (DBH), which converts dopamine (DA) to noradrenaline (NA); catechol-O-methyl transferase (COMT), which inactivates DA and NA; monoamine-oxidase (MAO) that is the primary inactivator of DA and NA; and serotonin (5HT). Results indicated that the undersocialized group had significantly lower DBH activity than either the controls or the socialized group. The socialized group had significantly higher activity than the controls. As regards COMT, activity was higher in the socialized group compared with both the undersocialized and the controls; the latter two did not differ in this dimension. There were no differences in MAO or 5HT.

According to Gray (1979, 1982) the principal neurotransmitter of the behavioral inhibition system is NA, while DA is apparently the principal transmitter for reward pathways (Olds & Fobes, 1981). Thus, if very low levels of DBH can be interpreted to mean the availability of an excess of DA but a diminished amount of NA (due to the lack of conversion of the former to the latter), then the reward system might be overenergized, while the inhibition system is transmitter-deficient (Quay 1986:51). In other words, the deficiency of dopamine means a deficiency in the reward system, which in turn encourages more excitement-seeking on the part of the ASP subject, while the deficiency of noradrenaline means less control of the inhibition system, which means more defiance.

Hyperactive Children and Antisocial Personality Disorder

Antisocial personality disorder and hyperactivity are different disorders, but it is possible that hyperactive children grow into adults who disproportionately produce psychopathic descendants (McCord, 1982:150-151). The hyperactive disorder, like ASP, also tends to run in families.

Contrary to the results with psychopaths, the injection of certain stimulants has the effect of reducing restlessness and increasing the levels of norepinephrene in the brain (Surwillow, 1990:105). Most of the studies of ERPs in hyperactive children agree that the ERPs are different from the ERPs of normals, and that the waveforms become "normalized" following treatment with stimulant drugs. There are, however, disagreements as to what are these actual differences.

Treatment for Violence

There are many drug treatments for violence, depending on the causes. There are anticonvulsants that are used for episodic dyscontrol syndrome; examples are carbamazepine and phenytoin, both of which have been reported to decrease the number of violent outbursts (Cummings, 1985:134). Propranolol blocks actions of some amines and prevents rage. Lithium is used for aggressive criminals, character disorders, and children manifesting explosive anger and hostility. The drug produces a decrease in the release of norepinephrine or an increase in the rate which norepinephrine is destroyed. Mania is treated with drugs that decrease norepinephrine levels (Groves and Schlesinger, 1982:453).

Other drugs for violence treatment are methylphenidate, used for attention-deficit disorder; hormonal agents that are antiandrogenic agents, such as medroxyprogesterone acetate and cyproterone acetate, that work to improve self-control of aggressive sexual impulses. Then, of course, there are the minor tranquilizers. And, finally, psychiatrists use neuroleptic agents and antidepressants when aggression is the result of psychosis or depression (Cummings, 1985:135).


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