Definition and Conceptual Background
Aggression is broadly defined as behavior intended to inflict physical or psychological harm on another individual.[1] Research in psychology, neuroscience, and sociology has consistently demonstrated that aggression is shaped by both biological and environmental determinants. This article reviews the current literature by addressing the biological and environmental foundations of aggression, followed by an interactionist perspective that integrates these dimensions.
Biological Foundations
Biological factors encompass the neurophysiological and genetic underpinnings of aggression:
- Genetic Factors: Twin and adoption studies highlight the contribution of genetic components to aggressive tendencies.[2] Specifically, the MAOA gene, which regulates serotonin metabolism, has been associated with heightened aggression.
- Brain Structure and Functions: The amygdala plays a central role in threat perception, whereas the prefrontal cortex is critical for impulse control.[3] Dysfunction in prefrontal cortical activity has been linked to increased impulsive aggression.
- Hormones and Neurotransmitters: Elevated testosterone levels and reduced serotonin activity significantly increase the likelihood of aggressive behavior.[4]
- Neurological Damage: Traumatic brain injuries and certain neurological disorders (e.g., epilepsy) are correlated with heightened aggression risk.
Environmental Foundations
Environmental influences stem from social, familial, and cultural contexts:
- Family Environment: Neglectful, authoritarian, or abusive parenting styles reinforce aggressive tendencies.[5]
- Social Learning: According to Bandura’s Social Learning Theory (1977), aggression can be acquired through observation. The well-known Bobo Doll experiments demonstrated that children imitate aggressive behaviors modeled by others.
- Societal Factors: Poverty, social inequality, and residence in high-crime neighborhoods elevate the risk of aggression.
- Media Influence: Exposure to violent media has been shown to increase aggressive behavior.[6]
- Stress and Substance Use: Alcohol and drug consumption impair impulse control, thereby lowering the threshold for aggression.
The Interactionist Approach
Modern psychology underscores that aggression cannot be adequately explained by biological or environmental factors in isolation. Instead, gene–environment interactions play a decisive role. For example, individuals with low-activity variants of the MAOA gene who also experienced childhood maltreatment exhibit significantly higher levels of aggression in adulthood.[7]
The origins of aggressive behavior are best understood through the interplay of biological predispositions and environmental influences. Consequently, effective interventions must address aggression at multiple levels: biological, familial, social, and cultural. Preventive strategies should combine individual-level treatments with structural reforms targeting broader societal conditions. Future research is expected to examine gene–environment interactions more comprehensively, thereby contributing to the development of evidence-based strategies to mitigate aggression.
[1] Anderson, C. A., & Bushman, B. J. (2002). Human aggression. Annual Review of Psychology, 53(1), 27–51.
[2] Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., … & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.
[3] Davidson, R. J., Putnam, K. M., & Larson, C. L. (2000). Dysfunction in the neural circuitry of emotion regulation. Science, 289(5479), 591–594.
[4] Dolan, M. (1998). The neurobiology of impulsive aggression. Personality and Individual Differences, 26(4), 679–689.
[5] Patterson, G. R., DeBaryshe, B. D., & Ramsey, E. (1992). A developmental perspective on antisocial behavior. American Psychologist, 44(2), 329–335.
[6] Huesmann, L. R., & Eron, L. D. (1986). Television and the aggressive child: A cross-national comparison. Hillsdale, NJ: Erlbaum.
[7] Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., … & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.
