Scientists in the fields of psychology, sociology and biology are interested in understanding the complex behavior of pathological aggression. For the purposes of this article, aggressive behavior refers to a range of behaviors that can result in both physical and psychological harm to oneself, others, or objects in the environment.
People with structural abnormalities and neurochemical imbalances are likely to engage in aggressive behaviors, then those who do not (Raine et. al., 2000, Rutter et. al., 1998). In recent years, neuroscientific studies have confirmed that several regions of the brain, including the amygdala, hypothalamus, and periaqueductal gray are involved in recognizing an acute threat and generating an emotional response (Sanchez et. al., 1998). Damage to the prefrontal cortex has especially been linked with reduced cognitive capacity and a triggered limbic system response and malfunction of the ventromedial and orbitofrontal sub-regions of the brain (Raine et. al., 2000). There regions have been associated with higher levels of impulsive behavior, with deficits in the withdrawal system, a system that promotes retreat from aversive and dangerous situations and a lack of emotional intelligence (Rutter et. al., 1998).
Adrian Raine and colleagues (1998) have conducted the largest and most thorough study to date, in which they used positron emission tomography (commonly called a PET scan) to compare brain activity in 41 convicted violent offenders to activity in 41 age matched control subjects. They found that the people convicted of murder had reduced activity in the prefrontal cortex and increased activity in subcortical regions such as the thalamus. This finding fits nicely with previous research showing that the damage to the prefrontal cortex impairs decision making and increasing impulsive behavior.
Imbalances in certain hormones, like testosterone and cortisol, and neurotransmitters, like serotonin and dopamine, may also be linked to aggression as well (Teicher et. al., 2003). These imbalances can occur for several reasons, including genetics, substance use, experiences of trauma, malnutrition, etc. (Kaufman et. al., 2000). Birth complications (e.g., fetal alcohol syndrome, poor maternal nutrition, and stress, etc.), acquired brain injuries, substance use, experiences of trauma, etc. Raine et. al. (1994) argued that protein synthesis can significantly impact executive functioning – sustained attention, behavioral flexibility to changing contingencies, working memory, self-regulation and inhibition, abstract decision making, planning and organization (Sonuga-Barke et. al., 2008).
Stress management during pregnancy could reduce pregnancy-induced hypertension and hypoxia to the fetus. In addition, healthy parenting programs may help parents to understand the effects of their discipline on their children's mental health. Research on childhood trauma demonstrated a significant correlation with hyperactivity, aggression, and violence (Kaufman, 2000).
In sum, aggressive behavior refers to a range of behaviors that can result in both physical and psychological harm to oneself, others, or objects in the environment. There are biological and environmental factors that can influence the onset and trajectory of aggression and violence. Prevention and intervention (e.g., maternal care, prevention of brain injuries, etc.) of cognitive disorders can improve long-term outcomes for individuals at-risk for aggression and violence.
References
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