Criminality is a multifaceted issue that is influenced by the presence or absence of several factors. The nature of these factors varies from biological and psychological factors, to social and environmental factors. As a multidimensional construct, criminality cannot be fully understood through the use of one perspective exclusively. As a complex issue, criminality requires attention to various perspectives in order to gain a comprehensive understanding of the causes and prevalence of criminal behavior. The factors that influence criminal behavior can loosely be grouped into three categories, including biological, environmental, and psychological factors. Thorough investigation of these three types of factors may yield insight into the causes and issues involved in criminal behavior.
Historically, possible biological factors involved in criminal behavior received much attention. Hereditarian claims in the United States between 1900 and 1940 argued that violent and criminal behavior had a strong genetic or neurogenetic basis (Allen, 2001). For example, Hooton claimed that, as a class, criminals possess distinct anthropometric characteristics, which included smaller body size, ectomorphic (lanky, thin) body build, straight hair, mottled eye color, shorter and broader noses, flatter ears, and a lower and more sloping forehead. Hooton also claimed that categories of criminals can be distinguished by anthropometric features. For instance, he claimed that murderers and robbers tend to be tall and thin, whereas killers, forgerers and conmen tend to be tall and heavy. Burglars, on the other hand, were claimed to be small and thin, while rapists and other sex offenders are short and heavy. Furthermore, Hooton also claimed that American-born and nine different ethnic or racial stocks differ significantly from each other in physical characteristics and the types of crimes they commit. Hooton based his claims on inferior biology, in that the degree and type of inferiority disposed one to crimes, while the environment called them forth. Of course, these claims hold no merit under the scientific scrutiny used according to today's standards, and there is an understanding that such false claims based on physical and racial characteristics are dangerous in their possible implications. However, biology has been found to play a role in criminality to certain extents.
Lee & Coccaro (2001) investigated the neuropharmacological influences involved in criminality and aggression. These researchers suggested that impulsive aggression has a role in both criminal and non-criminal behavior, and that an impulsive crime is essentially not synonymous with a premeditated one. They also suggested that impulsive aggression probably has a significant genetic, heritable component, although a single gene for aggression has not been found. It is possible that future research may find a polymorphism or combination of genes that contribute to the expression of an impulsive-aggressive phenotype.
Lee & Coccaro (2001) also discussed the role of deficient serotonergic function in behavioural disinhibition and the expression of impulsive aggression. This role has been demonstrated through the reduced levels of CSF 5-HIAA that have been associated with violent criminality. Furthermore, the serotonergic system is also very responsive to environmental factors, particularly early disruptions in development and early exposure to abuse or trauma. Impulsive aggression may be an aspect of personality that is relatively stable over a period of years, heritable, and correlated with biological variables. Therefore, the role that serotonergic functioning plays in the presence of impulsive aggression can only be understood in the context of a complicated relationship between genetics, biological processes, psychological functioning, and environmental influences.
Moreover, the expression of impulsive aggression and violent behavior is more than likely a mix of genetic and environmental factors. Lemonick (2003) claimed that a disposition for criminal behavior is determined early in life, suggesting a strong correlation between a harsh childhood and criminality later on. This author suggested that criminal behavior may be linked to a defective gene that made too much of an enzyme called monoamine oxidase A. This results in excessive destruction of neurotransmitters that help keep people calm and happy. However, many violent criminals do not exhibit this gene, while many non-criminal individuals do. This is where environmental factors possibly come into play, influencing whether or not the violent effects of the gene will be exhibited.
Lemonick (2003) explained how scientists have discovered that neither genes alone nor childhood abuse alone could explain adult violent behavior. However, a study examining boys who had both genetic mutation and early abuse indicated that 85% of these boys had committed a violent act as an adult. Furthermore, genes may influence people's susceptibility or resistance to environmental factors that are harmful, such as abuse. Someone with a low genetic predisposition for criminal behavior may have to be pushed to extremes to become violent, while an individual with a high genetic predisposition for criminal behavior might commit violent acts more easily.
Wilson (2002) described a longitudinal study that took place in 1972 that examined the MAO A genotype in the participants and periodically assessed the subjects' history of abuse and criminal convictions, their disposition for violence, as well as any symptoms of anti-social personality disorder. The results of this study indicated that only 12% of children that experienced abuse had low MAO A levels, and these accounted for almost half of their generation's convictions for violent crime. The researcher indicated that the combination of abuse and the genetic variation magnified the odds of criminal behavior by nine times, and that low levels of MAO A did not predict anti-social outcomes. Conversely, the enzyme's relation to aggression only emerged when consideration was given to whether the children were abused.
Testosterone is often considered to be related to aggression, given its increased concentration in males vs. that in females. An article entitled "Testosterone's family ties" that appeared in Science News maintained that there is in fact no link between testosterone concentrations and either delinquent behavior or depression in children and adolescents of both sexes if their relationships with parents are close. Furthermore, this article explained how behavior and mood problems most often seen in children are due to poor parental relationships. In a study, boys with high testosterone levels that related well to their mothers engaged in far fewer delinquent acts that boys with low testosterone levels that did not get along well with their mothers. Like that seen with genetic factors, testosterone levels of children create behavioural predispositions that get modified by the quality of parent-child relationships. The article described a good parent-child relationship as one in which the parent knew about and approved of the child's activities, the parent took part in activities with the child, and the child reported they felt close to the parent.
However, this article did report an interesting sex difference that emerged four children with less than adequate relationships with parents. Among these children, boys of all ages with higher testosterone concentrations were more prone to delinquency, while among girls, delinquent behavior most often appeared in those with low concentrations of testosterone between the ages of 10 and 14. The reasons for these observed sex differences were reported to be unclear.
Neuroimaging studies of antisocial behavior have been conducted, that have attempted to determine physical and neuroanatomical aspects of criminal behavior (Bassarath, 2001). According to Bassarath (2001), structural studies have tended to indicate that functions of the temporal lobe are implicated in criminal behavior, especially with respect to sexual offenders. However, several studies have yielded negative findings, which renders these studies inconclusive. Functional studies have also implicated the role of the prefrontal cortex, specifically the medial and lateral areas in antisocial behavior. Prefrontal reductions in the brains of men with antisocial personality disorder have been demonstrated through studies that quantify gray matter deficits in the frontal lobe. Also, work using PET has demonstrated high right-sided subcortical activity in affective murderers, and other systems, including the amygdala, brainstem nuclei, basal ganglia, and association cortex are likely involved and awaiting further clarification.
Bassarath (2001) explains the limitations of the existing literature. First, as of yet, there are no published functional MRI studies that look at antisocial behavior. Second, There are not any studies, as of yet, which examine possible developmental precursors of antisocial behavior in children and adolescents. Third, there are few biological studies that test interactions between biological vulnerability, psychological risks, and social factors. Fourth, the lack of specificity of phenotypic variants is a major hurdle that must be overcome in order to understand the underlying neurobiology of persons with antisocial behavior or violent tendencies. Fifth, and finally, translating neurobiological research into preventions, treatments, and policy may continue to pose challenges.
Another biological factor that may influence or cause criminal behavior is brain damage caused by viral infection (Tselis & Booss, 2003). Tselis and Boos (2003) explain how infections of the central nervous system can damage the brain and cause abnormal behavior, and that behavior is affected by damage to different parts of the brain. Examples of infections that may ultimately cause abnormal behavior include neurosyphilis, encephalitis, lethargica, herpes simplex encephalitis, and various other acute and chronic viral encephalitides. The researchers indicate that some cases of violence and other criminal behavior are the…