Monoamine oxidase A is an enzyme that breaks down important neurotransmitters in the brain, including dopamine, norepinephrine, and serotonin. The enzyme is regulated by monoamine oxidase A gene (MAOA). Humans have various forms of this gene, resulting in different levels of enzymatic activity. People with the low-activity form (MAOA-L) produce less of the enzyme, while the high-activity form (MAOA-H) produces more of the enzyme.

 

The MAOA gene causes an increase in serotonin within the brain. Usually serotonin has calming and relaxing properties but in the case of the ‘warrior gene’ the opposite occurs. The whole brain becomes 'soaked' and saturated in this enzyme, therefore the brain becomes insensitive towards it and the calming properties are lost.

It is thought that this gene is passed through generations via women/mothers as it is a mutation of the 'X' chromosome. This also suggests why more men and boys become criminal psychopaths as only sons get passed the 'X' chromosome from mothers where as a daughter can get one ‘X’ chromosome from the father and one ‘X’ from the mother, therefore it is more insignificant. However for a son, he can only inherit the ‘X’ chromosome from his mother increasing the likely hood that, that will be the MAOA gene.

 

Research has shown that aggression tends to show more characteristic wise with provocation. Study carried out by professor Rose McDermott (2008) at Brown University asked investigated how provocation affects levels of aggression due to the warrior gene.  Participants were directed to inflict physical pain on someone they believed had taken money from them by administering varying amounts of hot sauce.

A total of 78 subjects took part in the experiment over networked computers (all were male students from the University of California–Santa Barbara). Each subject (A) first performed a vocabulary task in which they earned money. Then they were told that an anonymous partner (B), linked over the network, could choose to take some of their earnings away from them. The original subject (A) could then choose to punish the taker (B) by forcing them to eat unpleasantly hot (spicy) sauce — but they had to pay to do so, so administering punishment was costly. In reality, the “partner” who took money away was a computer, which allowed the researchers to control responses. No one actually ingested hot sauce.

The findings are published in the Proceedings of the National Academy of Sciences.

Their results demonstrate that:

Low-activity MAOA subjects displayed slightly higher levels of aggression overall than high-activity MAOA subjects.

There was strong evidence for a gene-by-environment interaction, as MAOA is less associated with the occurrence of aggression in the low-provocation condition (when the amount of money taken was low), but significantly higher levels of aggression in a high-provocation situation (when the amount of money taken was high).

 

 

 

 

 

 

 

 

 

 

 

 

 

The results supported previous research suggesting that MAOA influences aggressive behaviour, with significant implications on decisions and behaviours such as aggression, violence, political decision-making, and crime. Several further studies have found a correlation between the low-activity form of MAOA and aggression in observational and survey-based studies.

Only about a third of people in Western populations have the low-activity form of MAOA. By comparison, low-activity MAOA has been reported to be much more frequent (approaching two-thirds of people) in some populations that had a history of warfare such as Germany, japan and Korea. This led to a controversy over MAOA being named the “warrior gene.”