Aggression (warrior gene) AQA A2 Psychology

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MAO-A- the warrior gene (AO1)

Men can inherit a genetic mutation which causes a deficicency in monoamine oxidase A (so they inherit the warrior gene)

MAO-A is an enzyme that causes a breakdown of excess monoamine neurotransmitters in the brain such as dopamine and noradrenaline.

The warrior gene is found on the X chromosone (so its more prevalent in men as women are protected by their other X chromosone)

Men who inherit the genetic defect on the X chromosone will have an imbalance of some neurotransmitters because not enough MAO-A has been released to break them down.

This imbalance causes the individual to become aggressive when under stress.

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IDA for warrior gene

Determinist and socially sensitive

The warrior gene explanation is biologically determinist.

It is effectively saying that men carrying the gene will be aggressive and when they are it cannot be deemed their fault as its all biological.

It has been shown that people with the gene are not aggressive and those without the defect are very aggressive so it doesnt appear to be a logical explanation.

This also makes it socially sensitive:

if its all biological no responsibility can be placed on the individual.

It could lead to society attempting to eliminate this gene through abortion etc in order to reduce aggression.

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Brunner 1993 supporting evidence

tested the urine of an aggressive dutch family who all inherited the defect warrior gene.

The 5 men tested with the defective gene had imbalanced levels chemicals thatr result from neurotransmitters.

This indicates the men were aggressive due to an imbalance of chemicals caused by the defect.


This research supports the genetic explanation as the men who inherited the gene showed clear signs of violent behaviour such as ****, arson etc.

leads to the conclusion that this genetic mutation of MAO-A is linked to their violence

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Vishnivetskaya et al 2007

Studied mice with the warrior gene (TG8 mice) and a control group who didnt have the defect.

The TG8 mice showed increased aggression towards intruder mice and increased territorial aggression, preditorial aggression and isolation induced aggression.

However, the didnt show incerased aggression in all form (E.G they were not more aggressive to juvenile mice)


This study partially supports the theory as it shows mice with the gene showing a general increased aggression.

HOWEVER, the behaviour was somewhat selective indicating other factors may play a role in aggression.

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AO3 warrior gene

Brunners study was based on one Ducth family making it hard to generalise.

Mice were used in Vitnivestskeya's study with may also be problematic when generalsing to the human population.

Ethical issues with studying animals?

The genetic explanation is therefore not completley persuasive because:

1) more research needs to be conducted to investigate genetic causes

2) there is not a clear cause and effect relationship  with males who inherit this gene#

3) recent research has discovered links with risk taking behaviour rather than aggression

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