Over the past two decades a significant amount of research has been undertaken that attempts to identify the connection between variations in brain structure and brain functioning with emotions, personality traits, and behaviors; this body of research has generated empirical evidence implicating variations in both brain structure and function in the development of practically every conceivable antisocial phenotype, especially aggression and violence (Beaver, 2013). Although Wright, Tibbets, and Daigle (2008) caution that some of the conclusions drawn from research into variations in brain structure and functioning are still preliminary and not well-established, the fact that there is a link between said variations and criminal violence is clear.
Two primary sections of the brain have been linked to the development of aggressive behaviors, primarily through the development of strong emotional responses combined with limited rational ability to regulate said responses: the limbic system and the frontal lobe. It is worth noting that multiple brain structures have been implicated in affecting behavior in addition to these two regions, especially the midbrain area including the pituitary, hypothalamus, cingulate gyrus, caudate nucleus, and ventral tegmental area (Wright et al., 2008).
Within the limbic system, the amygdala, which is responsible for emotions and partially responsible for memory, has been found to directly influence changes in violent or hostile activity (Wright et al., 2008). Also in the limbic system, the hippocampus, which is the primary memory center in the brain, is responsible for individuals' ability to anticipate or comprehend cause-effect relationships; an ability that has been found lacking in criminals, especially in violent offenders (Wright et al., 2008). Wright et al. (2008) state that these two brain structures, working together, are believed to be the most important sections of the brain that control emotions, survival responses (e.g. fight or flight response), and social responses (e.g. jealousy, anger). In addition, neuroimaging studies show structural and functional differences in the limbic systems of psychopaths as opposed to non-psychopaths, and spouse abusers have more active limbic systems combined with lower activity in the prefrontal cortex, which is examined below, than non-spouse abusers (Beaver, 2013).
The frontal lobe, which is the anterior portion of the cerebral cortex and located right behind the forehead, is the brain structure most implicated in the development of criminality (Wright et al., 2008). A healthy frontal lobe controls emotional impulses and drives rational thought, with injury to the area affecting an individual’s ability to control emotional impulses; in fact, damage to the frontal lobe results in severe mood changes, inflexibility in cognition, and a high inclination toward violent behavior (Wright et al., 2008). According to Wright et al. (2008), studies have linked frontal lobe damage to feelings of indifference toward the consequences of affected individuals’ behavior as well as impulsiveness. It is also important to note that the frontal lobe does not become fully developed until the mid- to late twenties as opposed to the limbic system, which becomes fully developed around the onset of puberty (Beaver, 2013).While this last fact could help explain the onset of delinquent and antisocial behaviors in adolescence and the “aging-out” of criminal involvement by most youth, it is also important when considering the ability of individuals to control emotional impulses.
Beaver (2013) describes the current state of research into brain structure and function with regard to criminality best, stating that empirical evidence supports the theory that both brain structure and function are directly associated with violence, psychopathy, and psychopathic personality traits. Further, the research has shown that criminals and individuals exhibiting antisocial phenotypes possess variations in brain structure and function that increase activity in the limbic system while also possessing an underactive frontal lobe (Beaver, 2013). In effect, the brain is unable to regulate impulses and emotions properly in criminally violent individuals.
Beaver, K. (2013). Biosocial criminology: a primer. (2nd ed.). Dubuque, IA: Kendall Hunt
Wright, J.P., Tibbetts, S.G., & Daigle, L.E. (2008). Criminals in the making: criminality across the life course. Los Angeles: Sage.