Different Types of Aggression
Aggression is complex, as it is composed of a number of different types of behaviour.
In 1968, Moyer presented a classification of seven forms of aggression from a evolutionary and biological point of view.
Predatory aggression: attack on prey by a predator.
Inter-male aggression: competition between males of the same species over access to resources such as females, dominance, status, etc.
Fear-induced aggression: aggression associated with attempts to flee from a threat.
Irritable aggression: aggression induced by frustration and directed against an available target. For example, we are irritated that someone pulls out in front of us in the car, but go home and shout at our partner.
Territorial aggression: defence of a fixed area against intruders, typically co specifics.
Maternal aggression: a female’s aggression to protect her offspring from a threat. Paternal aggression also exists.
Instrumental aggression: aggression directed towards obtaining some goal, considered to be a learned response to a situation.
Currently, researchers have identified two broad categories of aggression:
- Hostile/Affective/Retaliatory aggression
- Instrumental/Predatory/Goal Orientated aggression.
Research has indicated that people who tend towards affective aggression tend to have lower IQs than those with a tendency towards predatory aggression.
THEORETICAL APPROACHES TO AGGRESSION
Freudian Theories
In his early theory, Freud asserts that human behaviours are motivated by sexual and instinctive drives known as the libido, which is energy derived from the Eros, or life instinct.
Beginning in early childhood, individuals learn that some libidinous behaviours are disapproved of and cause unpleasant consequences such as punishment or withdrawal of affection. As the growing person learns to suppress undesirable libidinous behaviours, they are displaced into other behaviours such as aggression. Thus, the repression of such libidinal urges is displayed as aggression.
Drive Theories
Another means of categorising aggression is through drive theories, which attribute aggression to an impulse created by an innate need. The most well known drive theory of aggression is the frustration-aggression hypothesis proposed by a group of researchers at Yale led by Dollard. In this theory, frustration and aggression are linked in a cause and effect relationship. Frustration is the cause of aggression and aggression is the result of frustration
Social Learning Theories
Unlike the other models, social learning theory does not attribute aggression to an internal mechanism. There are two important principles underlying this theory: one is that aggression is initially learned from social behaviour, and the other, that once learned, aggression is maintained by other conditions.
There are a variety of proposed methods through which aggression is learned and maintained. One method of learning aggressive behaviour is through simple operant conditioning. If after performing an aggressive act an animal or human receives a positive reinforcement (such as approval or a toy), they are likely to repeat the behaviour in order to gain more rewards.
This has been demonstrated in countless research articles. One of the most famous studies of aggression in social learning was by Alfred Bandura who showed that social modelling of aggression led to increases in aggressive response rates by children.
Biological and Evolutionary Theories
These theories see aggressiveness as beneficial. It allows for the survival and success of populations of aggressive species. As such, the strongest animals eliminate weaker ones and over the course of evolution the result is an ultimately stronger, healthier population.
This evolutionary theory of aggression is one of many biological theories where aggression is understood to be instinctual. Common to some of the other biological theories is the proposition that aggression is the manifestation of a genetic or chemical influence.
Aggression is often directed towards and originates from outside stimuli, but has an internal character. So, someone annoys us (outside stimuli) and this makes us angry and aggressive (internal reaction). Scientists have been able to look at the relationships between various parts of the body and aggression.
Brain and Aggression
Some researchers have looked at the brain to explain aggression. They have found at least two areas of the brain that affect or regulate aggression.
- The hypothalamus is believed to serve the role of regulating aggression. If the hypothalamus is electrically stimulated, it can cause aggression. It also has receptors that determine aggression levels, based on interactions with neurotransmitters, serotonin and vasopressin.
- The amygdala has also been shown to be an area that can cause aggression. Stimulation of the area can cause aggressive behaviour, whilst damage or lesions to the area can reduce a person’s aggression and competitiveness (Bauman et al, 2006).
Hormones and Neurotransmitters
Testosterone is a hormone commonly linked with aggression. Testosterone has been shown to correlate with aggressive behaviour in mice and some humans, but in other research there has been little evidence supporting a relationship between aggression in humans and their testosterone levels.
Serotonin has also been linked to aggression by actually reducing it. Vasopressin, norepinephrine (noradrenaline), cortisol and other neurotransmitters are also being researched to in an attempt to understand their links with aggression.
Genetics and Aggression
Is aggression inherited? It is hard to determine how much of aggression is due to nature and how much to nurture. Some studies on animals have shown that it is partly inherited at least. Some researchers suggest that some humans may have an ‘aggression gene’ (to put it simply).
This gene is then ‘switched on’, when the person is in the wrong environment. For example, if a child is born into an aggressive environment, their gene may be ‘switched on’ and the child becomes aggressive. This is obviously very simplistic, but further research is being carried out.
Other research involving fruit flies has found that a gene called the ‘fruitless’ can be mutated to cause male flies to fight more like females and vice versa.
Evolution and Aggression
Most researchers argue that aggression should be considered in relation to how it helps the animal to survive and reproduce. Animals use aggression to gain new territories, to protect the territories and secure them.
They will also use aggression to protect other resources, such as food, water, mating opportunities and so on. It is theorised that the ability of animals and humans to kill and be aggressive is a product of our evolutionary need for survival.
