In this blog post, we’ll examine the relationship between criminal tendencies, genetic factors, brain structure, and environmental factors from the perspective of neurocriminology.
On September 13, 1848, a large-scale rock blasting operation was underway in the Green Mountains of Vermont. Phineas Gage, the foreman, was tasked with loading explosives into holes drilled into the rock. At the time, the process involved placing the explosives in the holes, covering them with sand, and compacting the mixture using a tamping rod. However, an accident occurred during the process when an explosion took place before the gunpowder had been sufficiently covered. At that moment, the force of the explosion propelled a long, heavy iron rod through Phineas Gage’s skull. Remarkably, he did not lose his life and was able to survive thanks to treatment from Dr. John Hallow, the attending physician.
This incident sent shockwaves through the medical community at the time. It was not merely because a person had survived. It was because Phineas Gage’s personality changed dramatically after the accident. Before the accident, he was known as a diligent, responsible, and sociable person. However, after the accident, he began to exhibit impulsive, erratic, and aggressive behavior. This case is a prime example demonstrating that damage to specific areas of the brain can affect human personality and behavior, and it is still frequently cited today. In other words, it demonstrated the possibility that the biological element—the brain—and the psychological trait—personality—are closely linked.
The field of study that examines this relationship is neuroscience. Neuroscience investigates how the brain and nervous system influence human behavior and thought. Among its subfields, neurocriminology is the discipline that explores the relationship between criminal behavior and brain function, analyzing the role biological factors play in the process of crime. In this article, we will focus on the major research and issues in neurocriminology.
Early discussions of neurocriminology began with the Italian criminologist Cesare Lombroso. He argued that criminals possess specific physical characteristics and that these can be used to distinguish criminal tendencies. He observed that common physical characteristics appeared depending on the type of crime—such as theft or rape—and even claimed that criminal tendencies themselves were hereditary. However, these claims lacked verification based on modern scientific methodology and later faced severe criticism after becoming associated with eugenics. Ultimately, Lombroso’s theory is not scientifically accepted today.
Modern neurocriminology, however, differs significantly from Lombroso’s claims. Current researchers focus not on appearance or physical characteristics, but on how brain structure and function, as well as genetic factors, influence behavior. In other words, they seek to scientifically analyze the biological differences between people who commit crimes and those who do not. Adrian Raine, a leading researcher in the field of neurocriminology, argued in his book *The Anatomy of Violence* that understanding crime requires considering not only environmental factors but also biological factors.
In fact, some studies have reported associations between specific genetic factors and aggression and impulsivity. In particular, mutations in the monoamine oxidase A (MAOA) gene have been extensively studied. MAOA is involved in the breakdown of neurotransmitters such as serotonin, dopamine, and norepinephrine. Some studies have reported that aggressive or antisocial behavior tends to occur more frequently in individuals with low MAOA activity. However, it is generally understood that these effects are more pronounced when combined with environmental factors such as childhood abuse or neglect.
Furthermore, the frontal lobe—particularly the prefrontal cortex—plays a crucial role in impulse control, decision-making, and empathy. In the case of Phineas Gage’s accident, the damaged area is believed to have been in the frontal lobe. Several brain imaging studies have reported that some violent offenders tend to show lower-than-average activity in the prefrontal cortex. This suggests that aggressive behavior may increase when impulse control functions are weakened. Of course, these results do not apply to all offenders, nor do they imply that criminal behavior can be determined based on brain structure alone.
Such diverse studies suggest the possibility of a certain correlation between brain function and criminal behavior. However, many social scientists argue that environmental factors—such as family background, educational level, economic conditions, and social discrimination—play a more significant role in the occurrence of crime. This is because crime is, in fact, a complex phenomenon that cannot be explained by a single cause.
Most people believe that environmental factors have a major influence on the occurrence of crime. Indeed, poverty, domestic violence, abuse, neglect, and low educational attainment are known to be factors that increase the risk of crime. However, there are also cases that cannot be fully explained by environmental factors alone. One frequently cited case is that of Jeffrey Landrigan. Despite growing up in a relatively stable environment, he committed crimes repeatedly. Later, he met an inmate who bore a striking resemblance to him, and an investigation revealed that the man was his biological father, Darren Hill, which attracted significant attention. This case sparked a debate about genetic factors.
So, which should be given greater weight as the cause of crime: environmental factors or biological factors? To date, numerous studies have shown that crime is significantly influenced by environmental factors. In fact, many serial killers and violent criminals are known to have experienced abuse or severe psychological trauma during their childhood. Furthermore, it has been pointed out that overemphasizing biological factors carries the risk of stigmatizing certain individuals as potential criminals. This is because such stigmatization can lead to human rights violations and social discrimination.
On the other hand, there has been a growing call recently to conduct more active research into biological factors. This is because there is a growing recognition that punishment after a crime has been committed has its limitations, and that prevention is crucial. To prevent crime, we must understand its causes more accurately, and neuroscience and genetics can provide important insights in this process. Of course, this does not mean that we should screen everyone’s brains to identify potential criminals. Rather, the intent is to use this information to identify risk factors early on and provide appropriate education, counseling, and social support.
Adrian Lane has argued that an integrated approach, considering both genetic and environmental factors, is necessary for crime prediction. However, given the current state of research, no algorithm capable of predicting whether an individual will commit a crime with high accuracy has been put into practical use, and crime prediction technology remains at a stage requiring extensive scientific and ethical validation. Therefore, discussions regarding crime prediction must be conducted with caution.
We can no longer view the issue of crime through the simple dichotomy of environment versus biology. The body of research accumulated to date demonstrates that genetic and environmental factors interact in complex ways. For example, even in studies related to MAOA, crime is not determined by specific genetic traits alone. Even people with the same genetic traits can lead completely different lives depending on their upbringing, education, and social experiences. Therefore, the key to crime prevention lies not only in identifying risk factors but also in creating an environment that can mitigate them.
This is also why social scientists take a cautious approach to crime prediction based solely on biological factors. If we emphasize biological information alone, important social issues such as poverty, discrimination, domestic violence, and educational inequality may be overlooked. Conversely, however, it is also undesirable to ignore biological research entirely. A more realistic approach is to develop an integrated model that considers both biological and environmental factors. This will enable the design of more sophisticated crime prevention policies and social support systems.
The brain and crime are distinct concepts but are deeply interrelated research subjects. Neurocriminology is an attempt to scientifically elucidate this relationship, and much more research is expected in the future. Of course, because human behavior is extremely complex, crime cannot be accurately predicted based solely on brain structure or genes. Nevertheless, this research can provide important insights for crime prevention, recidivism prevention, and the development of mental health support systems. Ultimately, what matters is not stigmatizing specific individuals, but rather creating a social environment that makes crime less likely to occur and identifying risk factors early to provide support. When we achieve a balanced understanding of both biological and environmental factors, we will be one step closer to a safer and healthier society.
