Some researchers maintain that there is a biological basis for crime and violence, theorizing that biological and genetic factors affect the brain and central nervous system in ways that lead to delinquent behavior. Biological theories (sometimes called trait theories or positivism) of crime and violence focus on how a youth’s brain and central nervous system respond to the world, and conclude this response is the basis for criminality. To the biological theorist, delinquency is not a youth’s choice, but rather a product of biological and genetic factors (or traits) outside the offender’s control.
Biological theorists view delinquency as “deviant” or “abnormal.” They consider crime to be a product of physical or psychological traits, including intelligence quotients (IQs) and body types. Biological theorists believe that the scientific method can be used to measure the traits of delinquent (abnormal) youths, with such youths being compared to nondelinquent (normal) youths to determine which traits are connected with crime and violence.
Early biological theories focused on the physical features of delinquents, stating that they “looked” different from non-offenders. Cesare Lombroso (1835-1909), an Italian physician, was the first to put forward this theory. He is considered to be the father of criminology. According to Lombroso’s theory, which he termed “criminal atavism,” delinquents were biologically and mentally less evolved than the average person. While Lombroso was a believer in the theory of evolution, he did not believe that all people were equally evolved. Notably, he viewed delinquents as “throwbacks” to earlier stages in the evolutionary process.
Lombroso’s research focused on the measurement of teeth, eyes, ears, jaws, and arms of offenders, and compared these measurements to those in the general population. Often, the larger the features, the more they resembled animal features; thus Lombroso stated that such characteristics were indicative of lesser stages of human evolution. He also researched other features, including purported insensi-tivity to pain, cruelty, impulsiveness, and tattooing. The more of these features a delinquent exhibited, the more Lombroso thought it likely that the individual was inclined toward criminality. In short, he suggested that criminals were born that way. Lombroso is called the father of criminology because he was the first to apply scientific principles to the study of crime. He carefully measured his subjects of study, recorded his findings, and based his theories on those findings.
Later, English physician Charles Buckman Goring (1870-1919) built on Lombroso’s theories. Using scientific methods of measurement and observation, Goring concluded that Lombroso’s theory of criminal atavism was incorrect. Goring theorized that delinquency was closely linked to a condition he called “defective intelligence”–an inherited trait passed on from parents. Based on this reasoning, Goring believed that delinquency could best be eliminated by regulating who could have children. People who were deemed to be feeble-minded, were epileptic, or had a history of mental illness or had “defective social instinct” were best prohibited from having children, he suggested.
Researchers who agreed that delinquency was an inherited condition expanded on Goring’s work. Richard Louis Dugdale (1841-1883) and Arthur H. Estabrook traced the family trees of delinquents and criminals in an attempt to determine whether criminality is inherited and delinquency is genetically based. Both of these social scientists studied a particular family who had a crime record going back generations. The Juke family was written about in 1875 by Dugdale (The Jukes: A Study in Crime, Pauperism, Disease, and Heredity) and in 1916 by Estabrook (The Jukes in 1915). Dugdale found that from the 1700s to the mid-1870s, the Juke family had produced 7 murderers, 60 habitual thieves, approximately 90 other criminals, 50 prostitutes, and 280 paupers. Estabrook, who followed up Dugdale’s work 41 years later, identified a further 378 prostitutes, 170 paupers, and 118 other criminals in the Juke family tree.
Other researchers suggested that body type is an indicator of a propensity toward juvenile delinquency and criminality. William H. Sheldon, for example, thought that some body types make youths susceptible to delinquency. Seldon identified four different body types: (1) endomorphs–soft, round, overweight people; (2) mesomorphs–large, athletic, muscular people; (3) ectomorphs–thin, fragile, weak people; and (4) balanced (normal)–not overly fat, thin, or muscular. Sheldon’s theory, called “somatotyping,” stated that mesomorphs were the most likely to be associated with delinquency and crime because they had the body type inclined to be the most aggressive and violent.
More modern social scientists focused on the biological and genetic make-ups of delinquents, in the belief that crime and violence are genetically inherited, just like hair and eye color or height. In the 1920s, German physician Johannes Lange conducted a study to determine a genetic link to crime. Although his study was criticized for weaknesses in his research methods, Lange reported a strong link between genetics and criminality. Lange’s findings were extended in the 1960s through the work of European researchers Karl O. Christiansen and Sarnoff Mednick. In their study of Dutch twins born between the years 1881 and 1910, Christiansen and Mednick found significant statistical support for a link between crime and genes.
In investigations similar to the twin studies, other researchers sought a possible link between delinquency and adoption. In these studies, the criminality of parents was compared to that of their biological children who had been raised by adopted parents. In different adoption studies, researchers David Rowe, Sarnoff Mednick, and Jody Alberts-Corush all showed that delinquency–at least in part–is genetically linked. Recent studies seem to confirm these findings. In 2003, Jeanette Taylor conducted a similar study of teenaged male twins and concluded that violent and criminal traits were linked to genetic factors. It is worth noting that while these studies have produced statistically significant findings, the purported gene-crime link may be nothing more than an individual’s genetic trait interacting with certain environmental and social factors that bring out violent or criminal behaviors.
In recent decades, researchers have concentrated on biological theories based on biochemical factors, such as the impact of nutrition on crime and violence. These studies focus on intakes of sugar, food additives, vitamins, and minerals, as well as everyday exposure to minerals such as lead, copper, and zinc. In the 1980s, separate studies by Alexander Schauss and the team of J. Kershner and W. Hawke indicated positive behavioral changes occurred in delinquent youths when they were fed balanced diets. Both sets of researchers found that high-protein, low-carbohydrate, sugarless diets, with adequate vitamins and moderate intake of milk, significantly reduced delinquent behavior. Other experiments conducted in the New York City school system showed that students scored better on national achievement tests when they reduced their sugar intake and eliminated artificial flavors and preservatives from their diets prior to taking the tests.
Other researchers have explored a possible link between delinquency and hormone activity (especially testosterone and serotonin). Many hormone levels peak between the ages of 13 and 19, corresponding with times of high levels of violence and crime in youths’ lives. Studies have shown that hormonal changes in teens are linked to delinquency and crime, particularly for teenage boys.
Biological theories of juvenile violence and crime also focus on neurological factors. These theories study the brain and nervous system of delinquent offenders and compare them to the same systems in the average non-offender. As part of this work, researchers measure attention spans, learning ability, cognitive ability, brain waves, and heart rates. These social scientists believe that brain chemistry, as controlled by the endocrine system (glands that secrete hormones into the blood), is the key to understanding delinquent violence and crime.
Some neurological studies of children have pointed to identifiable brain defects as a key cause of violence and aggression. These brain abnormalities, often called minimal brain dysfunction (MBD), are frequently linked to a mother’s addiction to drugs or alcohol during pregnancy and result in low birth weight, birth complications, childhood head injuries, or other genetically inherited factors for her child. In separate studies conducted by Stephen Tibbetts and Jean Seguin, brain activity in affected youths showed chemistry that may be linked to violence, aggression, anger, and crime.
Specifically, some researchers are studying the potential relationship between learning disabilities (LD) and delinquency. Young people with learning disabilities have trouble reading, writing, listening, speaking, and organizing their thoughts. Learning disabilities are not associated with vision or hearing problems, motor handicaps, or mental retardation. Studies show that arrested and incarcerated children have higher rates of LD than the general population. In 1976, Charles Murray proposed two explanations for the high rates of LD youth in trouble. The first, which he called the “susceptibility rationale,” stated that LD offenders are impulsive, do not learn from experience, and stay engaged in violence or criminal activity despite being punished. The second, which Murray called the “school failure rationale,” suggested that LD youths act out violently or criminally because of their frustration at doing poorly in school.
Biological theories of juvenile crime and violence have been criticized on a number of grounds. Often, researchers have used populations of documented youth offenders as samples for their studies, making it difficult to determine whether these offenders are representative of all youth or representative of only offenders who were apprehended. Other criticisms of biological theories suggest that they are politically or socially motivated, harkening back to the eugenics movement of Nazi Germany. Biological theories also often fail to take into consideration social forces, individual factors, social class, and gender issues.
Proponents of biological theories stress that they do not view any biological theory as a generalizable explanation of all youth crime and violence, but simply suggest that biological theories can explain some aspect of delinquent behavior. The core principle of most biological theories is that some youth do have developmental issues that limit their ability to learn and cope with some situations and, as such, place these youths at a disadvantage in society. These developmental issues may be genetic, chemical, or hormonal and may manifest themselves as aggression, violence, or crime.
- Lombroso-Ferrero, G. (1911). Criminal man according to the classification of Cesare Lombroso. Montclair, NJ: Patterson Smith.
- Moffitt, T. (1993). Adolescent-limited and life course persistent antisocial behavior: A development taxonomy, Psychological Review, 100, 674-701.
- Raine, A., Lencz, T., Taylor, K., Hellige, J. B., Bihrle, S., Lacasse, L., et al. (2003). Corpus callosum abnormalities in psychopathic antisocial individuals. Archives of General Psychiatry, 60(11), 1134-1142.
- Rowe, D. (1995). The limits of family influence: Genes, experiences and behavior. New York: Guilford Press.
- Seguin, J., Phil, R., Harden, P., Tremblay, R., & Boulerice, B. (1995). Cognitive and neuropsychological characteristics of physically aggressive boys. Journal of Abnormal Psychology, 104, 614-624.
- Sheldon, W. (1949). Varieties of delinquent youth. New York: Harper Bros.