Aggression Photo courtesy of The American Psychological Association (APA)Opens in new window

Aggression is behavior that is intended to harm another individual. The harm may be either physical, such as a punch or a kick, or verbal, such as an insult. Social psychologists have long recognized two types of aggressions: instrumental and emotional.

Instrumental aggression occurs when an individual intends to harm someone to obtain a desired end. In this form, the act of harm may be regarded as the only way to achieve one’s goals. For instance, soldiers during war would likely explain their attack on the opposing forces in terms of instrumental aggression.

Emotional aggression, on the other hand, is behavior accompanied by both the means and the end and is often impulsive. The purpose of aggression in this case is solely to hurt. Hitting someone in a rage is an example of emotional aggression.

Certain neural systems within the brain are possible factors in aggression. Studies have found that stimulating the hypothalamusOpens in new window (Ferris et al., 1997) or the amygdale in hamsters increases aggressive behavior.

LeDoux (1986) has pointed out that the amygdaleOpens in new window contributes to aggression by activating the fight-or-flight responseOpens in new window, a physiological and psychological response associated with stress that involves preparing the body either to fight or to flee. Other brain areas that have been implicated in aggression include the hippocampusOpens in new window, prefrontal cortexOpens in new window, and septal nuclei.

Evidence consistently points to certain hormones and neurotransmitters (chemical messengers in the brain) as being involved in aggression. Studies have shown associations between aggression and the neurotransmitter (chemical messenger) serotoninOpens in new window as well as the hormone testosterone, especially in males. Randy Nelson’s (2005) book Biology of Aggression reviews the evidence on these chemicals, other hormones and neurotransmitters, genetics, and other biological aspects of aggression.

Evolutionary psychologists suggest that human aggression results from an innate motivation to protect the survival of their genes. The inhibited aggression against genetically related others (to the extent that that occurs) can be accounted for by this explanation.

From this point of view, there are sex differences in aggression. Males would be expected to aggress to achieve and maintain social status, while females would aggress to protect offspring.

Aggression seems to be affected by learning. According to social learning theoryOpens in new window, aggressive behavior is learned through the observation of others. Bandura, Ross, and Ross’s (1961) inflatable doll study showed that children who had previously observed an adult aggressing toward an inflatable doll were later more aggressive toward the doll than children who had watched an adult sitting quietly. The general results from this study have been replicated reliably. This line of research inspired studies about whether and how media violence may lead to aggressive behavior in young people.

Other topics in aggression include the influence of culture on aggression, social factors (other than social learning or culture) that affect aggression, personality and aggression, aggression in nonhuman animals, and war. The interest in aggression remains steady in both the social and biological sciences.

See also:
  1. Geen, R.G. (2001). Human aggression (mapping social psychology). Berkshire, England: Open University Press.
  2. Nelson, R.J. (Ed.). (2005). Biology of aggression. New York: Oxford University Press.
  3. Wallace, B.C. & Carter, R.T. (2002). Dealing with violence: A multicultural approach. Thousand Oaks, CA: Sage.
  4. Bandura, A., Ross, D., & Ross, S.A. (1961). Transmission of aggression through imitation of aggressive model. Journal of Abnormal and Social Psychology, 63 (3), 575 – 582.
  5. Ferris, C.F., Melloni, R.H., Koppel, G., Perry, K.W., Fuller, R.W., & Delville, Y. (1997). Vasopressin/serotonin interactions in the anterior hypothalamus control aggressive behavior in golden hamsters. Journal of Neuroscience, 17 (11),4331 – 4340.
  6. Freedman, J. (2002). Media violence and its effect on aggression: Assessing the scientific evidence. Toronto: University of Toronto Press.
  7. LeDoux, J.E. (1986). Sensory systems and emotion: A model of affective processing. Integrative psychiatry, 4, 237 – 234.
  8. Nelson, R.J. (Ed.). (2005). Biology of aggression. New York: Oxford University Press.