Biological Factors in Family Violence
The authors attempt to review these causes using biological, psychological, either acts of commission (physical, sexual, psychological abuse) or acts of. Ethology and its congeners (e.g., sociobiology, evolutionary psychology) . Thus, the spouse who defends herself or himself from verbal or physical abuse is to. Some well-known philosophers and psychologists have argued that this is the biological parents are much less likely to abuse or murder their own children.
Most play fighting among boys is just that—mutually enjoyable roughhousing that does little harm and in fact helps to establish group leadership. In adult male animals, dominance aggression is usually limited to dominance displays and contests of strength in which the use of dangerous weapons reserved for predators is inhibited. Similarly, dominance aggression is constrained in human societies by cultural controls, as well as by compassion for one's rival. These cultural controls include opportunities to compete non-violently, such as by procuring wealth that will allow a person to gain resources and by the availability of rewards for prosocial behavior.
One obvious threat to this system of controlled dominance competition in humans is the availability of firearms, which can overwhelm our evolved anatomical and emotional protections Lorenz, Unemployed, unmarried, young men committed a disproportionate number of homicides; these are men of low status rank who are, perhaps, desperate to maintain or enhance their meager social position. These "social conflict" homicides outnumbered those associated wiih committing a property crime by to But property crime itself often constitutes a form of competition to gain sexual opportunities.
Around the world, men who do not earn enough to help support a family are unlikely to marry or to stay married Goode, Most women expect a man to contribute to the family income, not merely to support himself. These researchers are not trying to excuse rape, but rather to explain it so it can be more effectively combatted.
Of course, many destitute young men do not resort to crime; perhaps they are less impulsive or violent, or have been raised to believe that poverty is more desirable than criminality. The dominance hierarchy model may also help in understanding some recent physiological research on aggression pertaining to a neurotransmitter: It is low in individuals with depression, which often entails feelings of failure.
Low serotonin is also correlated with committing impulsive acts of homicide—why? Low ranking monkeys, children, and men tend to exhibit rather high levels of aggression, probably because they get picked on and have to retaliate Weisfeld, Thus, Prozac and its congeners which raise serotonin levels reduce aggressiveness and increase self-esteem, presumably by enhancing feelings of dominance, or pride.
The answer seems to be that such actions would prompt a "rage reaction" in the victim, which would need to oppose any such attack vigorously. Animals tend to stay within the rules because the rules are enforced by the victim. In fact, fights are relatively rare once the animals work out their dominance hierarchy. Only when a subordinate tries to usurp a superior's prerogative or a dominant animal continues to attack a defeated animal that has submitted does retaliation typically occur.
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Because such retaliatory attacks are intense and feature threatening displays, they seem to be prompted by rage, or anger. Various sorts of violation of individual prerogatives seem to trigger angry aggression in animals: Similarly, human anger seems generally to be a response to violation of some social expectation or norm. Subjects report that they would be angered by being passed up by a bus driver, but only if the driver is supposed to stop there Pastore, Thus, frustration by itself—being thwarted in our purpose—does not consistently anger us, but being wronged does.
This "transgression-aggression hypothesis" Weisfeld, is confirmed by noting that anger is reduced by acts that restore equity: Note that anger can be dissipated even if the subject takes no action. However, aggressing against an "innocent" third party does not usually reduce anger.
This and other evidence has discredited the "catharsis theory" of aggression, the notion that aggressive energy can be drained off in harmless ways. The motivation to attack is aimed at punishing the transgressor; it would be maladaptive if the individual attacked any convenient target. Only by attacking the transgressor successfully or otherwise restoring equity does systolic blood pressure—the measure of anger used in much of this research—fall.
What sorts of offense provoke angry aggression in humans? Violent attacks are often precipitated by being treated in ways contrary to one's biological interests. Losing a mate is often a disaster to one's success in raising offspring, so it is not surprising that various mate-guarding behaviors to prevent such an outcome have evolved in pair-bonding species.
But mate guarding is not identical in the sexes Wright, Women in many cultures guard their sexual reputations assiduously; women may fear desertion by their mates and loss of the man's contributions. Consistent with this perspective, most fights between adolescent girls in a low-income neighborhood were found to stem from sexual insults Campbell, What about aggression directed against one's own children—how can this be explained in evolutionary terms? Doubtless, like all other mammals, humans have evolved parental tendencies.
However, parental behavior has evolved to benefit one's own offspring, not those of others. Animals and people are more solicitous of their own flesh and blood than of others' offspring Hepper, For example, the risk of child homicide by stepparents was about times that by biological parents in a U. Furthermore, children who are handicapped and, consequently, less likely to be reproductively successful themselves, are more prone to abuse and infanticide. In many mammals the mother assesses her newborns, and abandons those that appear abnormal.
Likewise, the stimulus characteristics of abnormal babies may cause their parents to bond less strongly to them, and not breastfeed them. These instances of abuse and homicide of children also may be conceptualized as occurring because the adult has been angered by the child.
Child abuse often occurs when the adult has been angered by the child's behavior, especially when the parent has unrealistic expectations of the child's abilities. But to some extent the child's abilities may be poorly developed because of a congenital condition, so parental genes may be involved.
How Can Evolutionary Psychology Help Explain Intimate Partner Violence? - Behavioral Scientist
As described above, we also serve our biological interests by aiding and defending other relatives with whom we share genes by common descent. For example, identical twins, who share all of their genes, have been shown to cooperate more than fraternal twins in a test situation Segal, Thus, it is not surprising that the relatives of a murder victim are often infuriated at the perpetrator.
The other side of this nepotism coin is that we are liable to aggress against nonkin. In this research the aggression of initial interest was violent crime, which may involve various types of aggression. In this case no attempt was made to identify these types of aggression. Instead, the emphasis was on the role of kinship in the cross-generational perpetuation of criminal aggression. A triracial sample of Detroit felons was studied.
As predicted, these men tended to report that, as children, they had had poor relationships with their mothers: Therefore, a cycle of criminality might be perpetuated across generations involving these family dynamics, as follows: Anxiously attached children might become criminals and have unstable romantic lives, leading to another generation of children from unstable families.
Many of these children would grow up in families with rivalrous half-siblings and stepsiblings of low consangunity. Their mother might resort to frequent punishment to settle these disputes, resulting in the pattern of anxious attachment that is associated with this parental style. Furthermore, the fathers might make little positive contribution due to family instability.
Further supporting the model, maternal punitiveness and paternal inattentiveness were both associated with number of convictions.
Data by other researchers confirm these relationships between variables. This study points out the importance of kinship in violence and—more broadly—of evolutionary principles in the study of behavior. It also illustrates the interaction of presumably evolved affinities for close kin with experiential factors such as maternal punitiveness, paternal inattentiveness, and family structure.
Of course, other environmental factors such as role models, television exposure, and unemployment also affect violent tendencies. But these seem to interact with biologically based processes too, such as parent-child bonding.
Take poverty for instance. In a sample of college students, Aytch and Weisfeld found that lower-income families tended to have more anxiously attached children.
Presumably, typical circumstances associated with low-income families interfere with the parent-child bonding process. In the sample of male offenders, those subjects who were anxiously attached were found to have more felony convictions. Poverty also tends to lower the marriage rate and hence undercut family integrity, thus contributing to the number of violence-prone men Wilson, Implications for Intervention The extent to which evolutionary and experiential factors influence aggressive behavior is of great concern to both developmental and forensic psychologists.
The aforementioned findings demonstrate the influences of genes on human aggression. Therefore, we cannot hope to make much progress in reducing aggression without taking these factors into account.
For instance, intervention programs to reduce violence have focused primarily on removing violent offenders from society. However, in spite of increased allocation of resources for detaining violent offenders, the number of offenders convicted and incarcerated each year steadily increases. These anxiously attached children exhibit an increased propensity toward criminal behavior when they reach adulthood.
Only abusers who had normal brain MRI and no history of head trauma, bipolar disorder, and schizophrenia were included in the study. Alcoholic abusers had significantly lower glucose uptake in the right hypothalamus compared to alcoholic non-abusers and controls, suggesting an abnormality in hypothalamic activity of alcoholic abusers.
Reduced correlations in glucose activity between various cortical structures and the amygdala were found in alcoholic abusers compared to the other groups. Several of these brain structures form circuits important for control and mediation of fear-induced aggression. Since alcoholic non-abusers did not did show decreased hypothalamic activity, the authors concluded that alcohol was not a likely explanation for group differences in activity.
Summary Taken together, these diverse studies attempt to more precisely define the brain dysfunction that is associated with IPV, and each of these areas of investigation focuses on a different level of dysfunction.
At the most basic level, neurochemical alterations in perpetrators, specifically excessive testosterone or reduced serotonin activity, reflect an alteration of neuronal function that can be simplistically thought of as promoting rapid responding to external stimuli.
Hypoglycemia may have a similar effect on the brain by impairing cortical evaluation of stimuli and the nuanced responses that promote non-violent responding.
Biological Correlates of Intimate Partner Violence Perpetration
At the morphological level, PET scanning shows that the connections between critical parts of the brain are disrupted in perpetrators. Such impaired neuronal connections may be related to alterations in neuro chemistry, or they may be the result of head injury.
Head injury, even if it is relatively minor, can result in disruption of the long myelinated axons that normally connect one part of the brain to another.
At the functional level, a grossly abnormal response to the panicogenic stimulant, sodium lactate, illustrates how brain dysfunction in perpetrators can manifest. While alcoholism is often associated with IPV, and may have important confounding effects on the brain, many of these studies controlled for this effect thereby demonstrating that alcohol consumption, by itself, cannot explain the abnormal brain function seen in perpetrators.
Hines and Saudino conducted the first empirical evaluation of genetic and environmental contributions to the use and receipt of psychological and physical IPV.
Correlational analyses within each class of twins indicated that monozygotes, unlike dizygotes, were significantly similar to one another in their frequency of physical and psychological IPV, as measured by the CTS2 Straus et al. Because similarity between twins varies with the degree of genetic relatedness, these correlations suggest that genetic influences may be important to the use of aggression. Univariate model-fitting analyses revealed the models that best fit the data attributed familial resemblance of physical and psychological IPV to shared genes.
The best fitting models included both genetic and unique environmental effects but not shared environmental effects. These results provide preliminary evidence suggesting that variability in IPV is, in part, genetically influenced. However, the molecular genetic basis for IPV remains to be studied.
The candidate-gene approach is one method that can be used to study the genetic influences on complex traits such as IPV by a generating hypotheses about the role of specific genes in the etiology of the behavior, b identifying variants in or near those genes that might either cause a change in the protein or its expression, or be associated with functional changes, c genotyping the variants in the population of interest, and d using statistical methods to determine if there is a correlation between those variants and the phenotypes of interest.
Candidate genes are selected where there is a priori evidence to hypothesize an association with the outcome of interest. The best candidates for study of behavioral phenotypes are functional polymorphisms or genetic variants that have already been shown to impact neurobiological pathways implicated in the outcome.
While IPV is undoubtedly influenced by the small effects of many genes, a growing body of literature suggests links between MAOA gene polymorphisms and behaviors associated with IPV including aggression, impulsivity, and antisociality and this research provides a useful example for how researchers might integrate molecular genetics into future research and conceptualizations of IPV.
Monoamine oxidase A MAOA is a mitochondrial enzyme involved in the metabolism of serotonin, norepinephrine, and dopamine. Six variants containing 2, 3, 3. These alleles have previously been dichotomized with the three-repeat variant as low-activity and longer alleles 3. Evidence from animal and human studies suggests that MAOA may play a role in the etiology of traits related to IPV, including impulsivity, addictive behavior, and aggression.
MAOA gene knock-out mice have elevated brain levels of serotonin and enhanced aggression Cases et al. Recent research on the social behavior of primates implicates the MAOA gene in primate aggression. Investigators have developed a four-grade classification scheme for describing conflict behavior across 16 species of Macaque on the basis of coding social behavior variables that resemble human behavior such as male-female dominance and aggressive and conciliatory acts.
Grade 1 species are characterized by highly hierarchical societies characterized by intense episodes of conflict between animals and low levels of conciliatory behavior, while grade 4 species are comparatively tolerant, displaying relaxed dominance, open relationships, and high levels of conciliatory behavior.
Using this taxonomy, Wendland and colleagues recently examined functional genetic variants underlying these inter-species differences in behavior and found that Macaque species exhibiting low confict grade 4 displayed little or no intraspecies variation in the MAOA-LPR genotype.
In contrast, grade 1 and 2 species were polymorphic at one or both of these loci suggesting a role for the MAOA-LPR gene in the etiology of conflict behavior in primates. For example, Caspi et al. In Caspi et al. Likewise, Foley et al. Collectively, these findings suggest a a link between the MAOA gene and social conflict behavior, and b an association between this gene and antisocial behavior with the latter being most likely to be observed in individuals with histories of trauma and abuse.
These findings should raise concern about conceptualizing IPV exclusively as the outcome of social learning processes and they underscore the importance of addressing genetic factors in future research in this area. Though it is unlikely any genes would confer risk for IPV specifically, it is conceivable that genetic polymorphisms indirectly influence the development of maladaptive patterns of behavior, including IPV, through their influence on mediating factors such as personality and psychiatric symptomatology.
Research on MAOA illustrates possible mechanisms by which the genes that regulate neurotransmitters and neuropeptides might give rise to problems in the domain of IPV.
Conclusions and Recommendations Biological correlates of IPV perpetration can be categorized into the following domains: Head injury rates among abusers have been consistently higher than those of the general population. Abusers have been distinguished from non-abusers on the basis of their performance on several neuropsychological measures, particularly those of verbal intellectual ability, executive functioning, and attention.
There is little to no evidence that physiological reactivity data reliably predicts IPV perpetration or severity. That antisociality, not IPV specifically, relates to hyperreactivity among low-level violent abuse perpetrators and hyporeactivity among more severely violent abuse perpetrators suggests that the relationships are not simplistic main effects. The decreased serotonin and increased testosterone levels found in some research with partner abusive males, in combination with their reduced hypothalamic activity and reduced correlations of activity between cortical and subcortical structures involved in control and mediation of fear-induced aggression, may predispose abusers to overreact, with violence, to actual and perceived threats i.
Variance in physical and psychological IPV has been shown to be accounted for by both shared genes between twin siblings and non-shared environments, suggesting that there may also be a genetic component to IPV. While research on the biological factors associated with IPV perpetration has produced findings to help explain the complex etiology of IPV, this literature suffers from a number of methodological limitations.
Many of the studies relied on small samples and included inadequate comparison groups, limiting statistical power and the ability to draw definitive conclusions. For example, some studies define abuse as one act of physical violence committed in the last year, while others look for more than 11 violent acts.Emotion, Stress and Health: Crash Course Psychology #26
Research would also benefit from a consistent method for classifying violence as mild, moderate, or severe. Finally, as researchers have relied on clinical samples, it will be necessary to determine if findings reported in this literature review generalize to non-clinical samples.
To date, research has been unable to reliably differentiate between nonviolent individuals and IPV perpetrators, or subgroups of IPV perpetrators, on measures of baseline physiological arousal and physiological reactivity. It is therefore not currently possible to use physiological data to distinguish IPV perpetrators and nonviolent individuals.
Inconsistency between studies in finding differences in stress reactivity between IPV perpetrators and non-violent individuals may be due to the unreliable nature of stress reactivity data. It is not uncommon, for example, for a constellation of physiological reactivity scores to vary for the same individual on the same stress task at different points in time e.
In addition, studies of physiological reactivity and IPV have primarily examined cardiovascular variables, such as changes in heart rate. However, other measures of autonomic activity, such as galvanic skin response GSReither do not map onto heart rate or do not occur immediately during a stressful situation e.
Further, rather than an absolute difference in response magnitude i. The literature would therefore benefit from research that compares the reactivity of IPV perpetrators and non-violent individuals at multiple points in time, by using multiple measures of reactivity, and by measuring not only reactivity to relationship discord, but also recovery from physiological reactivity.
Regarding neurochemistry, metabolism and endocrinology, George et al. The next step would be to explore the mechanisms underlying such differences. For example, it would be helpful to look at the interaction between alcohol use frequency and quantity and serotonin and IPV or the interaction between alcohol use and testosterone and IPV. Given that serotonin and testosterone may influence, among abusers, fear-associated behaviors and aggression, similar interactions may emerge.
Furthermore, to rule out subtle structural brain abnormalities modulating aggression in participants with alcoholism, diffusion tensor imaging DTIa relatively new MRI technique that delineates axonal fiber tract direction and organization Kubicki et al.
DTI could also be used in combination with functional MRI fMRI to investigate the connectivity of functional effects arising under threat arousal conditions. It is also important to consider that serotonin itself is a very complex neurochemical and that in addition to absolute levels of serotonin, serotonergic functioning also depends on the number and nature of serotonin receptors.
Further, the technology utilized in the studies cited did not directly measure serotonin levels, but rather levels of either metabolites of serotonin or blood levels of chemicals e. While metabolite levels are generally accepted as a proxy for brain serotonin levels, and George et al. To further determine, and perhaps more definitively distinguish, the genetic and environmental contributions to the familial resemblance of IPV, future studies would benefit from using larger samples of twins in which the number of pairs of monozygotic twins approximately equaled the number of pairs of dizygotic twins.
A more heterogeneous sample including more non-White males would make findings more generalizable and allow for the comparison of potential gender differences underlying genetic risk for IPV.
Furthermore, since non-shared environments among twins accounted for much of the variance in aggression in the Hines and Saudino study, a design that attempts to elucidate the characteristics of the unique environments contributing to aggression within twin members of the same family would be helpful.
In this way, manipulating or modifying the unique environment, i. It would also be useful to examine the mechanisms of genetic transmission, i. For example, it is possible that it is some heritable aspect of cognitive functioning, autonomic reactivity, or neurochemical imbalance that accounts, in some part, for IPV. To date, there are only two published studies that have determined the efficacy of treating aggressive behavior in IPV perpetrators with a drug.
No significant differences in efficacy for fluoxetine vs.
All subjects received inpatient alcohol treatment and supportive cognitive-behavioral therapy CBT. In addition, all participants, regardless of condition, exhibited significant reductions in physical and non-physical abuse, as measured by the Partner Abuse Scale Hudson, These results suggest that fluoxetine, in conjunction with CBT and alcohol treatment, may be useful in reducing anger and physical aggression in alcoholic perpetrators of IPV.
Less invasive than the use of drug therapies for aggressive individuals, the use of nutritional supplements to treat aggression offers promising results.
Each of the topic areas summarized in the current review shows promise for enlightening our understanding of intimate partner aggression. Inconsistencies and methodological weaknesses in the research literature also suggest ideas for future research. For example, DTI or PET imaging studies would improve the reliability and validity of self-reported head injuries, often subject to memory loss. Longitudinal studies in which assessments of IPV are made twelve months, two years, four years and eight years post - head injury may reveal differences in IPV among head-injured abusers and controls that are not immediately apparent.
Furthermore, longitudinal studies will allow us to evaluate the process by which IPV develops in head injured individuals, perhaps as a result of the deterioration in the marital relationship.
The purely biological perspective cannot account for individuals with normal brain function who nevertheless perpetuate violence; nor do all perpetrators suffer from a psychological disorder or abuse drugs and alcohol.
Certainly, these factors contribute to a large proportion of intimate partner violence. Evolutionary psychology is an approach to psychology that applies principles of evolutionary biology—evolution by natural selection, for example—to understand the structure and function of the mind for longer discussions, see herehereand here.
Evolutionary psychology essentially uses evolutionary theory as a framework to understand, explain, and generate hypotheses about psychology and behavior. Evolutionary psychology is often misunderstood or maligned.
Another misunderstanding—particularly relevant for understanding intimate partner violence—is the naturalistic fallacy. This is the notion that because something is natural then it must be good or acceptable. Applied to intimate partner violence, the naturalistic fallacy might allege that when psychologists propose an evolutionary explanation for intimate partner violence, they implicitly condone the behavior.
This is simply untrue. Evolutionary explanations for behavior bear no relation to the moral judgements of that behavior. Unlike the other explanations discussed above, evolutionary psychology can offer possible answers to deep why questions. Evolutionary psychologists do this by explaining intimate partner violence at two levels of analysis: The ultimate level of analysis explains why a trait or behavior we observe could have arisen via natural selection.
In other words, what could be the evolved function of, or reason for perpetrating violence against a romantic partner?
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The ultimate level addresses the why questions. The proximate level of analysis explains the immediate causes of a trait or behavior how traits and behaviors manifest. In other words, what were the visible causes or situation-specific factors that lead to violence?
Sociological, biological, and mainstream psychological explanations discussed above would fall under the proximate level of analysis.