... the University of Akron found that male rat aggression results from reduced levels of serotonin in the brain. These researchers therefore suggested that aggressiveness in human males is also the result of reduced levels of serotonin in the brain and is not a learned behaviour. Research was conducted on a colony of rats. By introducing new male and female rats to an established colony, the resulting behaviour could be observed. As expected, the males in the group reacted strongly to the introduced rats whereas the females did not. After the experiment, norepinephrine, dopamine and serotonin were measured in various regions of the brains by high performance liquid chromatography. Serotonin is one of several substances known to affect mood and aggression. The decreased serotonin in the male brain was associated with increases in aggressive behaviour. The Y chromosome governs serotonin levels. It can be concluded that when the Y chromosome is ...

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