A research led by the University of Chicago's Irving B. Harris Distinguished Service Professor in Psychology and Psychiatry, Jean Decety presents that the brain scans of murderers who had committed or attempted homicide had less gray matter as compared to those prisoners involved in other criminal offenses.
As Decety reports, the areas where gray matter was noticeably reduced were the regions of the brain responsible for processing of emotions, control of behavior, and perception in a social environment. He explains that the amount of gray matter in the brain correspond to the number of cells, neurons, and glia that are necessary in processing information. This then affects how the information processed in order for one person to feel empathy towards a person or in order for one to "control behavior" thus preventing reactions in a rather inconvenient social convention.
Along with other scholars, working with Decety was University of New Mexico neuroscientist Kent Kiehl who reported that the study had gone on for ten years, while they collected data over eight prisons in two states. He noted the results as remarkable while pointing out that the study involved the largest sample of its kind. This means that they were able to have control variables for some factors like psychosis, therefore not including in the study those people who suffered brain injuries in the past or had psychiatric disorders such as schizophrenia.
In the study, 203 people who were charged with homicide or attempt of homicide made up the first group, 475 of them who committed assault, robbery, or other crimes described as violent made up the second group, and the remaining 130 people who were involved in crimes described as nonviolent or minimally violent made up the third group.
Although the study involved a large group of participants, the researchers noted that there is still not enough data to prove the link between homicide and the amount of gray matter in the brain. To follow this research, Decety and Kiehl are now working on a study on high-risk men currently in their mid-20s to look at their brain scans as well. They are planning to predict possible homicidal behavior in the future based on the image of the same regions of the brain as they identified in the recent study. With this, they hope to conclude whether or not the results of the first study would be enough proof for the relationship.
