Anthropological research data has shown the violence is an inherent conduct among the primate species (Walker, 2001). In society, criminal violence is a common occurrence and legislators have suggested that the behavior of criminals be analyzed in order to identify any psychological patterns that are consistent among these particular types of individuals.
In the past few decades, neurobiologists have proposed that an individual’s condition, which encompasses empathy, morality and free will, is holistically influenced by the frequency of stimulation and assembly of the neurons of an individual. Such notion is contradictory to the concept of Cartesian dualism, which states that the brain and the mind are two independent entities that coordinate with each other.
To date, the accumulation of research reports from the field of neuroscience is gradually affecting the concepts and effectivity of the justice system because of the shifting in the concept of human behavior and response to different stimuli. Neuroscience has influenced our current understanding of the multiple factors that govern violent behavior among criminals.
The 19th century classic report of Phineas Gage regarding the anti-social behavior that emerged after massive damage of the prefrontal cortex of his brain from a railroad accident is now considered as the birth of the field of forensic neurology (Harlow, 1848).
Today, computerized imaging of his fractured skull has shown that the autonomic and social nerve systems are the specific damages that were affected, thus resulting in a totally different individual.
Such observation, together with research results gathered from war veterans, has led to the conclusion that violent criminal behavior is caused by injuries to the frontal lobe of the brain. It has then been proposed that injury to the prefrontal cortex of the brain causes a condition that has been coined as acquired sociopathy or pseudopsychopath (Blair and Cipolotti, 2000).
It is interesting to know that there is an 11% reduction in the size of the grey matter of the prefrontal cortex among patients diagnosed with anti-social personality disorder (APD) (Raine et al., 2000). A related observation has also been observed between intelligence and alterations in the grey matter of the prefrontal cortex.
The temporal lobe of the brain has also been determined to influence an individual’s emotional response and aggression, wherein lesions in the amygdale of the temporal lobe result in an individual’s failure to recognize fear and sadness among the faces of other people (van Elst et al., 2001).
The connection between the decreased expression of the monoamine oxidase A enzyme and reactive violence has already been established (Caspi et al., 2002). Monoamine oxidase A is responsible for the catabolism of monoamines such as serotonin (5-HT). The working hypothesis currently accepted is that the prefrontal-amygdala connection is altered, resulting in a dysfunctional aggressive and violent behavior, resulting in criminality in particular individuals.
Earnest A. Hooton (1887 – 1954) is a highly acclaimed physical anthropologist and evolutionist. Much of his work focused on interindividual variations based on physiological and anatomical characteristics, including measurements of buttock-knee lengths as the main basis for constructing seats for the Pennsylvania railway trains. Hooton was also recognized for his concepts in primatology and comparative anatomy as basis for explaining differences in the human as well as primate species.
He was successful in describing a primary race, of which can be further subdivided in several racial subtypes. He is a proponent of the concept of eugenics, which involves genetic selection of traits that are deemed beneficial to the current population. The field of eugenics has been an interest in the field of biology and medicine because it facilitates the creation of new haplotypes that may be positively selection in the course of evolution.