Discuss one Biological and one Psychological Explanation of Aggression

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Discuss one biological and one psychological explanation of aggression (25 marks)

Some biological psychologists point to the role of neural and hormonal mechanisms in aggression. Hormones have already been implicated in a number of other psychological disorders, e.g., depression and eating disorders.

Studies have found a strong, positive correlation between levels of testosterone and aggression. This applies to both men (Olweus et al 1988) and women (Ehlers et al, 1980). Clare (2000) noted that girls with the condition congenital adrenal hyperplasia – which is implicated in high levels of aggression – engaged in more ‘rough and tumble play’. Testosterone appears to be most influential at two stages of life – a few days after birth i.e. ‘the critical time period’ when sensitisation of neural circuits happens and in adulthood when testosterone modulates neurotransmitter pathways.

Hormones are definitely at least linked to behaviour – although a problem exists in trying to establish cause and effect, which will be discussed later. Much human and non-human research points to a link between the two. For example, when levels of testosterone peak at the time of puberty in young human males, aggression also peaks.

Many non-human animal studies support the idea that aggression is somehow caused or linked with testosterone. One such method of testing this is to castrate various animals. This always leads to a marked decrease in aggression. Furthermore, when testosterone is replaced by hormone therapy in the castrated animals, the aggression of the animal returns to its pre-castration level (Simpson, 2001). This seems to support a causation effect or at least a link between the two. A similar study on cockerels by Berhold found the same effect.

More specifically, it seems that androgen stimulation in the early days after birth (up to ten days) causes changes in the neuronal system, which affects the level of aggression of a person through into adulthood. Women are typically less aggressive because their brains contain beta blockers which block most of the effect of the testosterone in the brain. Male mice who are castrated straight after birth throughout their whole life – even if they are given hormone therapy, i.e. huge doses of testosterone, later on in life. If the castration occurs 10 days after birth, the difference in aggression levels is much less obvious. This is supposed to be because of the androgen stimulation in the neural circuits during the early days after birth (Motelica-Heino et al 1993).

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The usual explanation for the link between testosterone levels and aggression is that testosterone interacts with androgen or oestrogen receptors. During the critical time period, testosterone sensitises certain neural circuits in the brain. This allows for the effects that testerone have which last into adulthood. Testosterone can affect the effect of neurotransmitters, e.g. how fast they move and the amount of neurotransmitter released. It appears to act upon serotonergic synapses, lowering the amount of serotonin available for synaptic transmission. The significance of this is that serotonin inhibits aggression, so less serotonin means more aggression. To prove this, Simpson (2001) ...

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