According to a US study of prisoners convicted of murder or delinquency, the brains of murderers have gray matter deficits in brain areas that have an impact on empathy or moral decision-making.
From Jack The Ripper to Charles Manson via Emile Louis, the murderers have always aroused curiosity. Whether it’s the general public, writers or scientists, everyone is trying to understand what’s going on in the head of a murderer. While much research has already been done on the subject, proving that the brains of perpetrators of homicide volunteers are different from that of “normal people”, American researchers have today managed to go further, discovering “for the first time the existence of brain abnormalities that distinguish the murderers from the perpetrators of violent aggression or non-violent antisocial acts “. The results of this study, the largest ever done on the subject, appeared in the journal Brain Imaging and Behavior.
Researchers from Albuquerque University (New Mexico) and the University of Chicago (Illinois) followed 808 men held in US jails. Taking care not to take into account individuals suffering from psychotic disorders or who had lost consciousness for more than two hours because of a brain injury, they separated the persons responsible for homicides (203 individuals), the violent offenders who did not commit homicide (475) and non-violent or non-violent offenders (130) in three separate groups. They studied their brain using an MRI. At the same time, they considered some factors such as drug use, age or IQ of the participants as well as their time of incarceration.
Conclusion: the murderers’ brains are slightly different from the offenders (violent and non-violent). However, researchers found no significant difference between the brains of violent and non-violent offenders. Thus, the neuroanatomy of a murderer would be special.
Scientists have been able to observe deficits in several brain areas. “Gray matter reductions among homicide offenders were evident in a number of important areas of the brain for emotional treatment, social cognition, and strategic behavioral control,” the study said. Most of the regions identified appear to play roles considered relevant to homicide. Scientists believe, for example, that some of these regions have an impact on empathy, guilt, emotional regulation or moral decision-making.
These results coincide with previous studies. Several studies had already shown reduced activity in several brain areas of the murderers, especially in the prefrontal cortex, an important area for, inter alia, moderate social behavior, and in the amygdala, very important in the management of emotions. These studies, however, were not as comprehensive as this one, as the researchers followed exclusively participants deemed “not guilty for insanity”. Thus, every discovered brain difference could as well have been caused by a mental illness or a brain injury.
However, the current study also has some limitations. Although they have taken many factors into account, researchers may have ignored important parameters such as impulsivity. Neuroanatomical changes may just mean that murderers are more impulsive than those who commit less violent crimes, concede the researchers. What’s more, they examined the inmates’ brain scans without being able to determine when brain changes had occurred. A crucial question remains unanswered: were individuals convicted of murder born with these deficiencies, or did they evolve over time?
From these results, scientists want to continue their research to determine how and why these neuroanatomical changes occur, whether they can be reversed or prevented and whether this could change the behavior of the murderers. Work that “represents a further step in securing our society by demonstrating the crucial role of brain health and development in the most extreme forms of violence represented among antisocial populations,” they conclude.
Every day in the world, 541 people are killed, 197,333 a year. The countries with the most killings are in order: Brazil, Mexico, Russia, the United States, Estonia, Chile, and Israel.