Theory of Aggression: Testosterone

• Hormones are chemical messengers that transmit information around the body through the blood stream.
• They are involved in the regulation of our physiology and behaviour including breathing, temperature, metabolic rate, reproduction, stress, growth and development, sleep and mood
• They are produced and excreeted by glands and this system of glands is called the endocrine system

Testosterone has been linked to aggressive behaviour. It is an androgen meaning that it is a chemical that develops or maintains male characteristics. We all have testosterone in our bodies but it is present in a much greater degree in the average male compared to females.

Antenatal exposure to testosterone has an organising effect on the developing brain. During the critical period immediately following birth, testosterone sensitises certain neural circuits. It stimulates cell growth in areas of the hypothalamus and amygdala (which have a role in the perception and reaction to threats, which includes aggressive responses).

Castrated rodents show little or no aggressive behaviour. However, if testosterone is replaced, they will show typical aggressive behaviour. 

Injecting neonatal female rodents with testosterone made them much more aggressive when given testosterone as adults compared to female controls. This supports the idea that the sensitisation of neural cicuitry after birth is an important factor in the effect of testosterone release.

However, experiments on animals lacks generalisability as brain areas said to be affected by testosterone serve different functions accross species.

Looked at aggression and testosterone levels across the lifespan

Findings:

Testosterone levels increased during the early teens. There was also a strong positive correlation between aggressive behaviour and inter-male fighting.

Conclusion:

There is a link between testosterone and aggression.

Evaluation:

Correlation doesn't indicate causality and it might be that other variables, such as socialisation, affect these factors.

Looked at case studies of convicted sex offenders who had been castrated.

Findings:

The castration lead to a removal of aggression and loss of sex drive.

Conclusion:

Cause and effect relationship between testosterone and aggression.

Evaluation:

It is ethically questionable. There is also a lack of scientific rigour, such as having a control group and fully objective measures of aggression.

The theory could be applied to the drug treatment of violent offenders. If you can lower their testosterone levels, this could reduce their physical aggression.

• Useful that it is reductionist as it allows researchers to isolate variables, such as hormones, which are related to aggression.
• Much of the supporting evidence has been conducted on small mamals, such as rodents. This limits the generalisability of the findings as the brain areas said to be affected by testosterone serve different functions across species.

Learning theories suggest that how aggressive we are is a consequence of our learning experiences such as upbringing, parenting, peers, culture and the media.

In conclusion, the hormone testosterone as an explanation of aggression is reductionist as it oversimplifies the complex array of factors that determine how aggressive we are.