Like many kinds of behavior, aggressive behavior also comes in different flavors. The large difference here appears to be whether or not the aggression was premeditated. Reactive aggression seems largely elicited, but I would argue that it can also be trained elicited if a person drills an effective form of self defense for long enough; many fighters and martial artists will confess to the fact that their style “becomes them”. It is of course extremely beneficial to have defensive moves “becoming” reflexes, and no doubt reflects changes in the brain that have occurred in order to promote the defensive movements as a likely outcome when given the right (probably aggressive) stimulus.
Blanchard et al (1977) lists reactive aggression as “the ultimate mammalian response to a threat”, and explains that in response to a threat, “[Humans] freeze to distant threats, attempt to escape from closer threats, and then launch explosive attacks against threats that cannot be escaped.” The main brain regions involved in our reaction to a threat are the frontal cortex (medial and orbital), the amygdala, hypothalamus, and the periaqeductul gray (Blair, James et al. 2010, The Psychopath – Emotion and the Brain, Blackwell). A large component of reactive aggression, therefore, is promoted by the autonomic nervous system.
Neurological studies of instrumental aggression appear to be less numerous. It is easy to see that the use of aggression can help individuals (also groups and nations) to achieve their goals, and is typically used to force another into subordination, but can we talk about the neurology of instrumental aggression in the same way? Instrumental aggression seems to be a social phenomenon, where the aggression is initiated in the form of a gamble; the odds of the fight are considered in light of potential outcomes, and a decision is made to fight or not. But once the fight has been initiated, the very same systems that are involved in reactive aggression will come to life, and so in this sense, instrumental aggression is merely the choice to activate your reactive aggressive response, presumably because you have a high degree of confidence in the outcome.
It is this gambling that makes me believe that the reward circuitry in the brain must be activated when considering instrumental aggression and the potential outcome is being considered. If you consider instrumental aggression as a means to be rewarded, then this makes sense. I haven’t seen any studies that have explored this, and would be grateful if anybody knows if these areas have been explored. Instrumental aggression, to me, is simply our own ability to assess whether or not to risk placing ourselves in harms way in the light of the potential goals/benefits.
Copyright Jack Pemment, 2012
Author, Seeing Red